Citation
Applying Low Impact Development Strategies to High Density Residental Area

Material Information

Title:
Applying Low Impact Development Strategies to High Density Residental Area
Creator:
Fan, Tiantian
Place of Publication:
[Gainesville, Fla.]
Publisher:
College of Design, Construction and Planning, University of Florida
Publication Date:
Language:
English
Physical Description:
Project in lieu of thesis

Thesis/Dissertation Information

Degree:
Master's ( Master of Science in Architectural Studies)
Degree Grantor:
University of Florida
Degree Disciplines:
Architecture
Committee Chair:
Cohen, Donna L.
Committee Co-Chair:
Tilson, William L.

Subjects

Subjects / Keywords:
Bioretention areas ( jstor )
Green roofs ( jstor )
Pavements ( jstor )
Precipitation ( jstor )
Rain ( jstor )
Site plans ( jstor )
Soils ( jstor )
Storms ( jstor )
Stormwater ( jstor )
Surface runoff ( jstor )
City of Miami ( local )

Notes

Abstract:
Storm water in large amount from precipitation extremes create great risks on urban flooding and aquatic environment pollution. On the other hand, urbanization impact the natural drainage system by over using groundwater, replacing soil and vegetarians covered surfaces with impervious pavements, and polluting water resources with potential contaminants. Furthermore, urban sprawl makes the situation even worse by expanding the adverse impacts of urbanization. Realizing adverse consequences, such as increased traffic, habitat fragmentation and heath issue caused by Urban Sprawl, governments and planners seek to sustainable develop methods to transform the city pattern. High density development has become the trend. ( ,, )
Abstract:
Traditional urban drainage system controlling stormwater runoff relies on pipes, canals, pumping stations and other structure facilities which generally ends with centralized facilities and requires a large amount of space. In addition, large amount runoff in the early raining period can cause water bodies pollution, and draining water out sites quickly is also a waste of water resources. In contrast to conventional drainage 10 strategies focusing on “end”, Low Impact Development (LID) conducts stormwater runoff from the source. LID is a sustainable design method managing stormwater through creating a hydrologically functional landscape that mimics the natural hydrologic regime.
Abstract:
However, compared to the low density area, high density residential areas have less land for LID strategies while need more green infrastructures due to the higher population and impervious surfaces cover rate. Hence, researches about how to use Low Impact development strategies in high residential area with limited availability of open spaces are needed. In order to evaluate the effectiveness of Low Impact Strategies on high residential area and analysis the efficiency of LID plans with different spatial pattern, in the present study, a high density residential area in Miami is chosen as the study site, and four scenarios including predevelopment scenario, existing scenario, and two Low Impact development scenarios with different spatial pattern are simulated by using Storm Water Management Model (SWMM).
General Note:
sustainable design terminal project

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Tiantian Fan. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
1022120844 ( OCLC )

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APPLYING LOW IMPACT DEVELOPMENT STRATEGIES TO HIGH DENSITY RESIDENTIAL AREA By TIANTIAN FAN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE O F MASTER OF SCIENCE IN ARCHITECTURAL STUDIES UNIVERSITY OF FLORIDA 2015

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2 2015 Tiantian Fan

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3 To My Family

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4 ACKNOWLEDGMENTS Firstly, I would like to thank my parents for their continuous support of my life and study. They scarified a lot to make sure I can get the best education. And they give me a lot of freedom to choose the way I want to live. Moreover, I would like to thank my advisor Prof. Ding Jianmin in Huazhong University of Science and Technolo gy for giving me this valuable learning opportunity. I also would like to express my sincere appreciation to my advisor Prof. Cohen and Prof. Tilson for the guidance of my research Prof. Cohen helps me get the license of a software that plays a very imp ortant role in my research. My thanks also goes to Dr. Lu for his suggestion to my research. Last but not the least, I am grateful to my classmates for the sleepless nights we were working together before deadlines, and for all the memorable experiences a nd adventures we have had in Unite States, Singapore, and the Netherlands.

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5 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ ................................ ....... 11 Problem Statement ................................ ................................ ................................ ................................ 11 Objective and Scope ................................ ................................ ................................ ............................... 12 Research Significance ................................ ................................ ................................ .............................. 12 2 BACKGROUND AND LITERATUR E REVIEW ................................ ................................ .............................. 14 The climate change and urbanization impacts on urban hydrological environment ............................. 14 Traditional stormwater management ................................ ................................ ................................ ..... 16 Low impact development ................................ ................................ ................................ ....................... 17 Rain Garden /Bioretention ................................ ................................ ................................ ................... 18 Green Roof ................................ ................................ ................................ ................................ .......... 19 Permeable Pavement ................................ ................................ ................................ .......................... 20 Bioswales ................................ ................................ ................................ ................................ ............. 21 Effectiveness of Low Impact Dev elopment Practices ................................ ................................ ............. 22 Reduction of runoff ................................ ................................ ................................ ............................. 22 Reduction of pollutant load ................................ ................................ ................................ ................ 23 Cost ................................ ................................ ................................ ................................ ..................... 24 Maintenance ................................ ................................ ................................ ................................ ....... 25 Low Impact Development site plan method ................................ ................................ ........................... 26 LID Hydrologic Evaluation model ................................ ................................ ................................ ........ 26 Stormwater management case studies in high residential area ................................ ........................ 27 Summary of Literature Re view ................................ ................................ ................................ ............... 30 3 METHODOLOGY ................................ ................................ ................................ ................................ ...... 32 Introduction ................................ ................................ ................................ ................................ ............ 32 Site Description ................................ ................................ ................................ ................................ ....... 32 Climate Data ................................ ................................ ................................ ................................ ............ 33 Scenario Design ................................ ................................ ................................ ................................ ....... 35 4 SCENARIOS DEVELOPMENT ................................ ................................ ................................ .................... 38 LID Strategies Design ................................ ................................ ................................ ............................... 38 Non Directly Connected Impervious Areas (NDCIA) ................................ ................................ ........... 38 Parameters of LID control methods in SWMM ................................ ................................ ................... 38

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6 LID Scenario Design ................................ ................................ ................................ ................................ 44 Pre development condition ................................ ................................ ................................ ................ 44 Existing condition ................................ ................................ ................................ ................................ 45 LID site plan condition ................................ ................................ ................................ ......................... 46 5 RESULTS AND DISCUSSION ................................ ................................ ................................ ...................... 49 Comparing Pre development scenario and Existing site plan scenario ................................ .................. 49 Continuous model results ................................ ................................ ................................ ................... 49 Single event model results ................................ ................................ ................................ .................. 50 Comparing Existing site plan scenario and LID site plan L scenario ................................ ........................ 52 Continuous model resu lts ................................ ................................ ................................ ................... 52 Single event model results ................................ ................................ ................................ .................. 56 Comparing LID site plan L scenario and LID site plan H scenario ................................ ........................... 59 Continuous model results ................................ ................................ ................................ ................... 59 Single event model results ................................ ................................ ................................ .................. 62 Conclusion ................................ ................................ ................................ ................................ ............... 6 5

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7 LIST OF TABLES Table 2 1. Cost Comparisons Between Conventional and LID Approaches ................................ ................ 17 Table 2 2. The summary of maintenanc e difficult degree of LID strategies ................................ ............... 26 Table 3 1. Average evaporation rate during January to December in 2006 ................................ ............... 34 Table 4 1. Layer s consist of LID strategies in SWMM ................................ ................................ ................. 38 Table 4 2. Parameters of rain garden in SWMM ................................ ................................ ........................ 43 Table 4 3. Parameters of green roof in SWMM ................................ ................................ .......................... 43 Table 4 4. Parameters of permeable pavement in SWMM ................................ ................................ ........ 44 Table 5 1. Runoff of predevelopment scenario and existing site plan sce nario under continuous 5 years ................................ ................................ ................................ ................................ ................................ .... 50 Table 5 2. Runoff Existing site plan and Predevelopment in single events ................................ ................ 52 Table 5 3 Exceedanc es analysis of LID site plan L and Existing site plan (Exceedance threshold=0.02 cfs) ................................ ................................ ................................ ................................ ................................ .... 54 Table 5 4 Runoff summary of green roof, rain garden and permeable model ................................ ......... 56 Table 5 5. Runoff summary of Existing site plan and LID site plan L in single events ................................ 58 Table 5 6. Runoff of LID site plan L and LID site plan H under continu ous 5 years ................................ .... 60 Table 5 7. Exceedances analysis of LID site plan H and LID site plan L (Exceedance threshold=0.01 cfs) .. 61 Table 5 8 Runoff summary of LID site plan L and LID site plan H in single events ................................ .... 65

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8 LIST OF FIGURES Figure 2 1 Precipitation Worldwide 1901 2013 ................................ ................................ ...................... 15 Figure 2 2. Thompson Creek Flow Rates in Pre& Post Development Scenario ................................ .......... 16 Figure 2 3. Rain gardens. (Source: Collett, B., McCown, K., & Wall, S. (2013). LO W IMPACT DEVELOPMENT OPPORTUNITIES FOR THE PlanET REGION). ................................ ................................ ...... 18 Figure 2 4. Typical structure of green roof (Retrieved 07/13/2015 from https://greenerheights.wordpress.com/2012/04/22/the structur e of green roofs/) .............................. 19 Figure 2 5. The summary of percent runoff by bioretention, green roof and permeable pavement ........ 23 Figure 2 6. The summary of LID strategies cost ................................ ................................ .......................... 25 Figure 2 7. Cost per unit volume of runoff reduction. Data from D. Joksimovic and Z. Alam, 2014. ......... 25 Figure 2 8. The schematic of spatial pattern of Beijing Olympic Village (A) and Bishan Ang Mo Kio Park, Singapore (B) ................................ ................................ ................................ ................................ ............... 27 Figure 2 9.The aerial view of Beijing Olympic Village. ................................ ................................ ................ 29 Figure 2 10. The aerial view of of Bishan Ang Mo Kio Park. ................................ ................................ ...... 30 Figure 3 1. The high density residential site in Miami ................................ ................................ ................ 33 Figure 3 2. Rainfall data from 1/1/2001 to 12/31/2006 ................................ ................................ ............. 34 Figure 3 3. 100 year design storm ................................ ................................ ................................ .............. 35 Figure 3 4. The schematic of spatial pattern of four scenarios ................................ ................................ .. 37 Figure 4 1. Existing site plan ................................ ................................ ................................ ....................... 46 Figure 4 2. LID si te plan L ................................ ................................ ................................ ............................ 48 Figure 4 3. LID site plan H ................................ ................................ ................................ ........................... 48 Figure 5 1. Runoff of predevelopment scenario and existing site plan scenario under co ntinuous 5 years ................................ ................................ ................................ ................................ ................................ .... 49 Figure 5 2. Runoff of Existing site plan and Predevelopment under 2 year storm ................................ .... 51 Figure 5 3. Runoff of Existi ng site plan and Predevelopment under 50 year storm ................................ .. 51 Figure 5 4. Runoff of Existing site plan and Predevelopment under 100 year storm ................................ 52 Figure 5 5 Runoff summary of LID site plan L and Existing site plan through 2001 to 2006 ..................... 53 Figure 5 6 Frequency analysis of event volume of Lid site plan L and Existing site plan ........................... 55 Figure 5 7. Runoff of Existing site plan and LID site plan L under 2 year storm ................................ ......... 57 Figure 5 8. Runoff of Existing site plan and LID site plan L under 50 year storm ................................ ...... 57 Figure 5 9. Runoff of Existing site plan and LID site plan L under 100 year storm ................................ ..... 58 Figure 5 10. Runoff summary of LID site plan L and LID site plan H through 2001 to 2006 ....................... 59 Figure 5 11 Frequency analysis of event volume of Lid site plan L and LID site plan H ............................ 62 Figure 5 12. Runoff of LID site plan L and LID site plan H under 2 year storm ................................ ........... 63 Figure 5 13. Runoff of LID site plan L and LID site plan H under 50 year storm ................................ ......... 64 Figure 5 14. Runoff of LID site plan L and LID site plan H under 100 year storm ................................ ....... 64

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9 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Architectural Studies APPLYING LOW IMPACT DEVELOPMENT STRATEGIES TO HIGH DENSITY RESIDENTIAL AREA By Tiantian Fan July 2015 Chai r: Donna Cohen Cochair: William L Tilson Major: Architecture Storm water in large amount from precipitation extremes create great risks on urban flooding and aquatic environment pollution. On the other hand, urbanization impact the natural drainage syste m by over using groundwater, replacing soil and vegetarians covered surfaces with impervious pavements and polluting water resources with potential contaminants. Furthermore, urban sprawl make s the situation even worse by expanding the adverse impacts of urbanization. Realizing adverse consequences, such as increased traffic, habitat fragmentation and heath issue caused by Urban Sprawl, governments and planners seek to sustainable develop methods to transform the city pattern. High density development has become the trend. Traditional urban drainage system controlling stormwater runoff relies on pipes, canals, pumping stations and other structure facilities which generally ends with centralized facilities and requires a large amount of space. In addition, large amount runoff in the early raining period can cause water bodies pollution, and draining water out sites quickly is also a waste of water resources In contrast to conventional drainage

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10 ucts stormwater runoff from the source. LID is a sustainable design method managing stormwater through creating a hydrologically functional landscape that mimics the natural hydrologic regime. However, compared to the low density area, high density residen tial areas have less land for LID strategies while need more green infrastructures due to the higher population and impervious surfaces cover rate. Hence, researches about how to use Low Impact development strategies in high residential area with limited a vailability of open spaces are needed. In order to evaluate the effectiveness of Low Impact Strategies on high residential area and analysis the efficiency of LID plans with different spatial pattern, in the present study, a high density residential area i n Miami is chosen as the study site, and four scenarios including predevelopment scenario, existing scenario, and two Low Impact development scenarios with different spatial pattern are simulated by using Storm Water Management Model (SWMM).

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11 CHARPTER 1 INTROD UCTION Problem Statement According to Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, "The frequency of heavy precipitation events has increa sed over most land areas". (IPCC, 2007) Storm water in large amount from these precipitation extremes create great risks on urban flooding and aquatic environment pollution. On the other hand, urbanization impact the natural drainage system by over using g roundwater, replacing soil and vegetarians covered surfaces with impervious pavements thus acting against recharge process of groundwater; and polluting water resources with potential contaminants. ( WWAP 2015 ) Traditional urban drainage system controlling stormwater structure facilities which generally ends with centralized facilities and requires a large amount of sp ace. Furthermore, large amount runoff in the early raining period can cause water bodies pollution, and draining water out sites quickly is also a waste of water resources. ( Wang, Eckelman, & Zimmerman, 2013 ) In contrast to conventional stormwater runoff from the source. LID is a sustainable design method managing stormwater through creating a hydrologically functional landscape that mimics the natural hydrologic regime. (County, P. G. S. 1999). A study shows that, area with high impervious surfaces cover rate, such as high dense housing, down town and lar ge retail, also have high rate of stormwater surface runoff. (University of Tennessee, 2013). However, compared to the low density area, high density residential areas have less land for LID strategies while need more green

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12 infrastructures due to the highe r population and impervious surfaces cover rate. Hence, researches about how to use Low Impact development strategies in high residential area with limited availability of open spaces are needed. Objective and Scope The primary objective of this research i s to find out how to use Low Impact Development strategies in high density residential area. A high dense housing district in Miami, FL in US facing significant urban flooding issue is chosen to be the research site. The research plan is as follows: Evalua ting the effectiveness of different Low Impact Development strategies, including reduction rate of runoff and pollutant loads, occupied area and cost, by reviewing different Low Impact Development sit plans of high residential areas and relative researches Calculating site runoff under undeveloped conditions through SWMM Calculating site runoff under present develop conditions through SWMM Redesigning the high density residential site using LID practices in different patterns. Examining the effectiveness of LID site plans in runoff controlling through SWMM. Analysis and discuss the experiment results and drawing conclusions. Research Significance Realizing adverse consequences, such as increased traffic, habitat fragmentation and heath issue caused by Ur ban Sprawl, governments and planners seek to sustainable develop methods to transform the city pattern. Smart growth is a potential solution to the problem of urban sprawl, as it provide citizens walkable neighborhood, green spaces and convenient local fac ilities by increasing land use density. ( Resnik,

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13 2010 ) As increasing density and impact of climate change give potential pressures on urban drainage system, researches on how to apply Low Impact Development practices on high dense area have practical significanc e.

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14 CHARPTER 2 BACKGROUND AND LITERATURE REVIEW The climate change and urbanization impacts on urban hydrological environment The hydrosphere on the earth is a dynamic circulation system. The water cycle can be described as four steps including evaporation, condens ation, precipitation and collection. Sun drives the water cycle, warms water in waterbody. Then water vanishes as water vapor into the air. Air flows move water vapor and drop out of the upper air layers as precipitation. Most water falls go into the seas or onto arrive at downpour, where the water streams over the seas. Others are absorbed by earth and stored as ground water. After the water comes back to the sea, a new water cycle is about to begin. Both climate change and urbanization have impacts on wat er cycle process. According to the recording of temperature data from N OAA the global average temperature is increasing in recent decades. The warming atmosphere brings changes in weather and climate. In many places, changes in precipitation is obvious, l eading to hurricane drought, and flooding. Figure 2 1 shows the total annual amount of precipitation over land worldwide has increased since 1901. This graph uses the 1901 2000 average as a baseline for depicting The global warming not only changes the rainfall amount but also changes the precipitation pattern. Places already wet get more extra water vapor than dry area when temperature is increasing, which makes rainfall intensity increased in wet area while decreased in dry area. That means more floodi ng will happen in already wet urban area while already dry places will hardly get rainfall. Large amount rainfall will make significant pressure on wet drainage work, while dry area should consider about how to capture and restore the rare water resources.

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15 Figure 2 1 Precipitation Worldwide 1901 2013 On the other hand, urbanization also has significant impact on the evaporation and collection process of water cycle The urban development result in the reduc ing the vegetation and the compacting of the soil. The natural permeable surface is replaced by impervious concrete surface. Thus instead of being absorbed by soil and plants rainfall turns into runoff on hard surfaces such as parking lots, driveways and c oncrete squares. Significantly increased runoff can grow flooding risks. A study shows that the runoff for peak discharges are approximately doubled after development, as seen in the F igure 2 2 in Thompson Creek, Santa Clara Valley, CA. ( Mangarella & Palhegyi, 2002 ) Furthermore, urbanization brings potential pollutant. C oncentrated population generate a large amount of waste and pollutant, such a s heavy metal, bacteria and other sediment. When the surface covered by vegetarian, plants can sufficiently absorb and break down the pollution during rains. However, by running across of large impervious

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16 surface, the rainwater can collect more pollutants. Figure 2 2 Thompson Creek Flow Rates in Pre& Post Development Scenario Traditional stormwater management In tradition, the goal of stormwater management is to prevent flooding by using underground pipes, p ump station, and other structural measures to remove surface water runoff out of sites. However, this method has limitations such as high cost and environment pollutant since it is a single objective oriented design ignoring water cycle, landscape benefit s and wildlife habitats First, traditional methods are expensive. In order to process runoff centrally a huge amount of canals and underground pipes are needed to make up the drainage pipe net. Pump station also costs a lot since construction occupies ex pensive urban land. Table 2 1 shows cost of conventional methods can be as much as 80% more than LID Approaches. Second, water quality management cannot achieved easily in traditional drainage system. Traditional methods treat stormwater in the end, while pollution is generated on site. During conveying to the centralized treatment station, fast moving stormwater can erode ecological banks and

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17 lead to water quality deterioration. Growing bacteria in pipes and canals also treats urban hydrological environme nt. Furthermore, in most cases, conventional drainage strategies drains runoff out of the local watershed this can cause violation of water cycle balance. In many places small streams and lakes have been seen dried because of traditional drainage system cannot capturing the runoff for local watershed. (NIPC, 1997) Last, instead of vegetarian surfaces which can cooling down the runoff, the concrete drainage system can increase the temperature of the running through stormwater. This is problematic that war mer water can impact the wildlife habitat of fish and other aquatic organisms. Table 2 1 Cost Comparisons Between Conventional and LID Approaches Project Conventiaonal Development Cost LID Cost Cost Differen ce percent difference 2nd Avenue SEA Street $868,803 $651,548 $217,255 25.01% Auburn Hills $2,360,385 $1,598,989 $761,396 32.26% Bellingham City Hall $27,600 $5,600 $22,000 79.71% Bellingham Bloedel Donovan Park $52,800 $12,800 $40,000 75.76% Gap Cree k $4,620,600 $3,942,100 $678,500 14.68% Garden Valley $324,400 $260,700 $63,700 19.64% Low impact development Since its inception, Low Impact Development was raised to deal with growing urban drainage issues that traditional stormwater management method s could no long George's County, Maryland, in 1993.( County, P. G. S. 1993). Low impact development is an enhanced approach to achieve stormwater management by conserving natural resources, providing runoff storage, prolonging travel time and controlling discharge rate

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18 Comparing to traditional drainage strategies, LID strategies cannot only reduce runoff a nd pollutant, but also add value to landscape with a lower cost. Commonly used LID strategies include rain gardens, green roofs, permeable pavements, and swale systems. Rain Garden /Bioretention Rain gardens or Bioretention are shallow planted depressions d esigned to retain and infiltrate stormwater. (County, P. G. S. 1993). Rain gardens generally are consisted by drought tolerant plants, porous material, and bioretention soil. Figure. 2 3 shows an example of rain gardens. Figure 2 3 Rain gardens (Source: Collett, B., McCown, K., & Wall, S. (2013). LOW IMPACT DEVELOPMENT OPPOR TUNITIES FOR THE PlanET REGION ). As rain fall into bioretention, the stormwater is caught by vegetarian surface at first, then it wil l be absorbed and storied by bioretention soil level. Meanwhile suspended pollutants coming with stormwater are removed or mitigated through this subsidence and infiltration process and are further break down through biological treatment. At last, nutrient s and heavy metals will be absorbed by plants. In that way, rain gardens help

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19 reduce surface runoff and pollutant load. Rain gardens can be arranged among lawns, parking lots and pavement sides where directly connect to runoff. Sunny places are recommende d for locating rain gardens, since plants and soils can be fully drying out between storm events. Design guidelines recommend that bioretention systems occupy 5 7% of the drainage basin. Green Roof Green roofs, or so called vegetated roofs or living roofs are roofs covered by vegetarians and function as gardens on top of buildings without occupied extra urban land, which make it an idea strategy applied to stormwater management in high dense area. ( Berndtsson, 2010 ) There are multiple benefits can be contributed by green roofs, such as collecting rain water as water r esources, reducing stormwater runoff, reducing urban heat island, providing wildlife habitat and enhancing biodiversity. ( Bengtsson, Grahn, & Olsson, 2005 ; Takebayashi & Moriyama, 2007 ) In general, the construction layers typical for green roofs are vegetation layer, soil layer, webbing filter and drainage material. Figure. 2 4 shows the typical structure of green roof. Figure 2 4 T ypical structure of green roof ( Retrieved 07/13/2015 from https://greenerheights.wordpress.com/2012/04/22/the structure of green roofs/ )

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20 Green roofs can be classified as extensive and intensive types based on soil media, types of vegetation and thickness of substrate. The substrate layer of extensive green roof is about 150mm, while the depth of intensive green roof is more than 150mm. Extensive green roofs are mainly covered by Se dum species with easier maintenance and more often used for residential buildings. Intensive green roofs needs more maintenance jobs, since large plants and shrubs are planted. Unlike extensive green roofs providing limited spaces just for people doing mai ntenance on roofs, intensive green roofs are more open and accessible, thus are more appropriate to commercial and industrial area offering green public open spaces for human recreation activities on top of buildings. ( Berndtsson, 2010 ; Mentens, Raes, & Hermy, 2006 ) Permeable Pavement Traditional pavement generates about twice the impervious surface cover of bui ldings. As using of impervious material such as conventional asphalt and concrete, traditional pavement cannot infiltrate stormwater thus causing ponding and sheet flow in traffic area. ( Carlson et al., 2013 ) In contrast, permeable pavement is design to reducing runof f and pollutant loads by retaining and infiltrating rain water with proliferous surface and subbase. Permeable pavement can be used in parking lots, squares, and sidewalks where hard surfaces are required, beneficing pedestrians by cleaning flooded surface s. Permeable pavement can be flexibly used in design except sites with harmful substances or high sediment erosion. ( Collett, McCown, & Wall, 2013 ) There are six types permeable pavement including pervious concrete, porous asphalt, permeable interlocking concrete pavers (PICP), concrete grid pavers, porous gravel pavement and reinforced grass pa vement according to study of Ferguson. ( Ferguson, 2005 ) The most common permeable pavements among these permeable pavements are concrete gr id

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21 pavers (CGP), permeable interlocking concrete pavers (PICP), and permeable concrete (PC). These permeable pavements drainage stormwater in different ways. CGP have void spaces in both internal and between individual pavers. PICP are concrete pavers that leave void spaces at corners and midpoint of pavers during paving. PC is different from standard concrete in that accomplishing interconnected void spaces during curing process by removing fine aggregate from the compound. Permeable pavements achieve infi ltrating storm runoff via the existence or formation of these void spaces. ( William F. Hunt & Bean, 2006 ) Bioswales Bioswales are channels with slight slopes and covered by plants, designed to reduce surface runoff and improve stormwater quality by infiltrating and settling stormwater during the process o f conveying surface water slowly from walkways, roads, parking lots, and buildings. ( Ahiablame, Engel, & Chaubey, 2012 ) In urban area, bioswales are inexpensive and flexible strategies used along linear infrastructures. There are dry swales and wet swales two general types of bioswales. Dry swales are like bioretention described in 2.4.1 with vegetarian on the top, pre mixed soil media in base, and combing underdr ain system in the under base layer. Due to the linear feature of dry swales, they are more suitable used at highway median, low and medium density residential roadside, landscape buff, and the margins of small parking lots. Wet swales are more similar to linear wetland cells with wetland plantings and permeable ponds. However, bugs and odors generating in the aquatic environment can be problematic, when wet swales be used in high density residential areas. As limitation, both swales are not appropriate for ultra urban areas and stormwater hot spots such as

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22 gas station and popular shopping center, since limited penetrable spaces and high rate of pollutants. ( Clark & Acomb, 2008 ; Virginia, 2010a 2010b ) Effectiveness of Low Impact Development Practices Effectiveness of different Low Impact Development strategies can be evaluated in various aspects such as reduction percentage of runoff and pollutant load, constructio n cost, maintenance operability and consumers acceptable degree. Researches and practices in this field have been well documented. ( Ahiablame et al., 2012 ; Bowman, Tyndall, Thompson, Kliebenstein, & Colletti, 2012 ; Dietz, 2007 ; Joksimovic & Alam, 2014 ) Effectiv eness of Low Impact Development strategies such as bioretention, green roof, permeable pavement and bioswales are compared in this section. Reduction of runoff Bioretention, green roofs and permeable pavement can efficiently reduce stormwater runoff volum e and peak flow rate. According to the literature review of LID practice by Laurent M. Ahiablame, Bernard A. Engel and Indrajeet Chaubey. The runoff reduction rate of bioretention is from 40% to 97%. The rate is effected by rainfall intensity. Rain gardens can nearly capture the whole inflow rainfall in small rainfall events. ( Davis, 2008 ) The mean rainfall capture rate of green roof differs between 20% and 100%. Increasing the thickness of infiltrate s oil and roof media can improve the performance of vegetated roofs, while increasing rainfall amount can decrease the performance of the system. Permeable pavement can be one of the most effective strategies, since the average runoff reduction is between 50 % and 93%. A study by Fassman and Blackbourn (2010) even prove that pre development hydrology can be achieved with permeable pavement. ( Ahiablame et al., 2012 ; Fassman & Blackbourn,

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23 2010 ) Figure. 2 5 shows the summary of percent runoff by bioretent ion, green roof and permeable p avement Figure 2 5 The summary of percent runoff by bioretention, green roof and permeable pavement Reduction of pollutant load The amount of sediment removed from the runoff is mostly dependent upon (1) the speed at which the water flows through the filter, trap, or basin; (2) the length of time the water is detained; and (3) the size, shape, and weight of the sediment particles. (County, P. G. S. 1999). Bioretention has been proved the NO.1 LID strategy in efficiently removing sediment and nutrient losses by a large amount of practices. T he average reduction rate of metal is between 30% and 90%. The mean retention of bacteria ranges from 70% to 99%. The performance of bioretention is effected by scales, location, material and quality of maintenance. The reduction rate of sediment and nutri ents in permeable pavement varies between 0% and 94%. Average metal reduction ranges from 20% to 99%. Permeable pavement can also dissolve grease and bacteria such as E. doli and fecal Streptococci. Swales also can contribute a moderate

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24 reduction for heavy metals. However, thing are different in green roofs. Studies shows that green roofs can capture rainfall while no nutrition are retained. Furthermore, fertilization and unhealthy vegetation on green roofs can add hazardous substances such as NO3 N and P t o runoff. However, these adverse effect can be reduced by appropriate green roof media and combination with other LID strategies. For example, conveying the runoff from green roof to bioretentions is a good alternative to prove aquatic quality. ( Ahiablame et al., 2012 ) Cost Installation cost of Low Impact development strategies may be high in some situation due to costly vegetation covers, expensive permeable ma terials, filter underdrains and maintenance fees. Nonetheless, these costs can be offset by benefits including reducing cost of superabundance storm drainpipes, site grading, site paving, and landscape. In most practices, LID strategies can reduce cost ran ged from 15 to 80 percent in all comparing to traditional measures. Rain gardens and Green roofs can cost much than bioswales and permeable pavements, since the requirement of planting drought resistant plants and Landform treatment. And intensive green ro ofs can be most expensive one due to an extra fee of altering the building tops for large vegetation. Permeable pavement is the cheapest strategy with a cost range from $2.5 to $10 based on different types. For example, the price of interlocking concrete p aving blocks can be 4 times higher than asphalt. Cost ranges for these LID strategies are listed in. ( ABC, 2015 ; EPA, 2000 ) Figure. 2 6 shows summary of LID strategies cost. According to a study about LID strategies cost efficiency in runoff control by D. Joksimovic and Z. Alam, green roofs, the most costly practice, has the best cost efficien cy. Permeable

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25 pavement, the cheapest strategy ranking second in the list ( Joksimovic & Alam, 2014 ) Figure. 2 7 shows the cost efficiency of different LID strategies. Figure 2 6 The summary of LID strategies cost Figure 2 7 Cost per unit volume of runoff reduction. Data from D. Joksimovic and Z. Alam 2014. Maintenance Maintenance of LID strategies includes maintenance of vegetation material, infiltration soil and mulch layer. Depending on different structures, materials and scales

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26 of LID strategies, the maintenance frequency and cost varies. In general, the maintenance difficult degree of permeable pavement is high, because keeping permeability of the surface needs frequent vacuuming work. Rain gardens requires lower maintenance when plants are established. Maintenance works includes amending mulch layer annually, and r emoving erosion of berm following heavy rainfall. Green roofs should leave access for maintainers. The cost of intensive green roofs are higher than extensive green roofs. Maintenance difficult degree of these LID strategies is shown in. ( Collett et al., 2013 ) The summary of maintenance difficult degree of LID strategies are listed in Table. 2 2. Table 2 2 The summary of maintenance difficult degree of LID strategies Maintenance LID strategy Maintenance difficult degree Bioretention Medium Green roof Low to Medium (extensive), High (intensive) Permeable pavem ent High Vegetated swale Low Low Impact Development site plan method LID Hydrologic Evaluation model The software used in modeling is PCSWMM which is an advanced software built EPA Storm Water Management Model (SWMM) is a dynamic rainfall runoff simulation model used for single event or long term (continuous) simulation of runoff quantity and quality from primarily urban areas. The runoff component of SWMM operates on a collectio n of subcatchment areas that receive precipitation and generate runoff and pollutant loads.

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27 The routing portion of SWMM transports this runoff through a system of pipes, channels, storage/treatment devices, pumps, and regulators. SWMM tracks the quantity a nd quality of runoff generated within each subcatchment, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period comprised of LID practices at the software. St ormwater management case studies in high residential area High following, one is Beijing Olympic Vil lage in China, and another one is Bishan Ang Mo Kio Park in Singapore. Both plans of these two cases are high density residential area, but with different spatial patterns. The spatial layout of Beijing Olympic Village is inclined to equilibrium, while Bis han Ang Mo Kio Park is more concentrated. Stormwater Strate gies are applied in both cases. Figure. 2 8 shows the schematic of spatial pattern of the two cases. A B Figure 2 8 The schematic of spatial patt ern of Beijing Olympic Village (A) and Bishan Ang Mo Kio Park, Singapore (B)

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28 The case of Beijing Olympic Village The Olympic village in Beijing, China is World's Largest Green Neighborhood awarded LEED (Leadership in Energy & Environmental Design) Gold sta tus in 2008. It is designed for 16000 athletes including 42 six story to nine story residential buildings, five public buildings, and a few leisure clubs. Figure. 2 9 shows the image of Beijing Olympic Village. After the 2008 Beijing Summer Olympic Games i t has been converted to a residential area. As a high density residential area, land is limited. In order to maximum the green spaces, parking has been located underground. As a result, 90 percent of the landscaping are green spaces along with pedestrian a nd bike paths. Also, this strategy leaves spaces for stormwater management practices, such as infiltration trenches, rain gardens, permeable pavements and rainwater cisterns. Other strategies like green roofs, water efficient irrigation system and drought resistant and native vegetation are used to capture stormwater in the village. However, these strategies give more attentions to how to make the landscaping attractive and how to capture the rainwater but without advanced stormwater treating measures and c oncerns of urban flood control. A study which aimed at improving runoff control benefits demonstrates an evaluation of urban runoff systems on Beijing Olympic village by modeling techniques. ( Jia, Lu, Shaw, & Chen, 2012 ) As a result, some Low Impact Development strategies are added or modified in the recommended plan for Beijing Olympi c village, such as re routing runoff collected by green roofs through bioretentions before directly falling into the rain cisterns, prolonging flow detention times, and the use of properl y designed bioretention cells.

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29 Figure 2 9 .The aerial view of Beijing Olympic Village. The case of Bi shan Ang Mo Kio Park, Singapore Floods are a common occurrence in Singapore usually caused by a combination of heavy rainfall, high tides and drainage problems, especially in Low lying areas. Most floods in Singapore are flash floods that subside within a few hours. In order to solve the flood issue and create a joyful, beautiful and health hydrologic environment, Active, Beautiful, Clean Waters (ABC Waters) Programme is laun ched to integrate the traditional drainage facilities with the surrounding parks and spaces. Bishan Park in Singapore is a flag project of the ABC Waters Programme. The park is located between two high density housing complexes Bishan and Ang Mo Kio. Figur e 2 10 shows an aerial view of of Bishan Ang Mo Kio Park. The project transforms 3km of Kallang River from a linear utilitarian concrete drainage channel into a meandering natural river with eco embankment. When heavy storm comes, the park works as a over sized

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30 bioretention, capturing rainwater and runoff from surrounded high density spaces, and slowing down the water, thus reducing the hydraulic overload of the river in more dense urban areas downstream. Enough open spaces for this project are guaranteed by the building spatial pattern of this area. The highly concentrated residential buildings around this park not only meet the request of plenty rooms for citizens but also create a large open spaces for stormwater management practices. Figure 2 10 The aerial view of of Bishan Ang Mo Kio Park Summary of Literature Review As increasing inflow by growing extreme precipitation events and increasing impervious surfaces area by turning vegetarian covers into hard surface, climate change and urbanization bring a lot of challenge to stormwater management in high density area. Compared to the traditional ways which cost a lot and cause hydrological pollutant issue, LID is a more sustainable method to deal with ur ban runoff. However, due to limited space, applying LID to high density area can be challenging. Hence, how

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31 to design the spatial pattern of high density area in order to effectively apply the LID strategies needs to be studied.

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32 CHARPTER 3 METHODOLOGY Introduction This chapter describes the research method of building Low Impact Development evaluation model. First, introduce the location, land use, landform, and soil type of the study site. Second, describe the climate condition, including precipitation and evapora tion. Last, model the original site plan and two advanced site plan with different spatial pattern. Site Description The selected research site is a 7.24 acres high density residential area located in Miami, FL where rainfall intensity is higher than stat e average. This site is chosen from sites zoned RU 4, which means a high density apartment house district with a density above 50 units per acre according to Miami zoning code. Figure. 3 1 shows the existing site layout. The site is located near the Royal Galdes Canal which is connecting Maule Lake and other canals. According to the Flood Zones GIS data from FGDL, the site is in Zone AE, the flood insurance rate zone that corresponds to the 100 year floodplains. Hence, the 100 year storm standard is adopte d in the following design storm model. Terrain is another primary element in stormwater management. This site is flat with a slope less than 2%. The exactly soil data in FGDL for this site do not record the drainage and soil type. However, these data can b e achieved through analyzing of surrounding undeveloped parcels. Most soil type of surroundings are sandy. So when modeling the scenarios, sandy soil is concerned as the site soil type.

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33 Figure 3 1 The hig h density residential site in Miami Climate Data Continuous rainfall data, evaporation data and design storm are needed in SWMM modeling. The available rainfall data in the site area is from 1970 to 2006 obtained by the Fort Lauderdale, which is the neares t National Weather Service rain gage from the site. As rainy season of Florida is lasting from June to August, continuous rainfall data ranges from 6/1/2006 to 8/30/2006 is selected for the site. Figure. 3 2 shows this rainfall data. The corresponding evap oration data is also chosen from the same rain gage. Table 3 1 shows average evaporation rate during January to December in 2006. Design storm is precipitation pattern defined for use in the design of hydrologic system. According to the SCS rainfall distr ibutions map, the design storm for

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34 this site is SCS type Three return period, 2 year, 50 year and 100 year are discussed. Figure 3 3 shows 100 year design storm Frequency Analysis of Daily Rainfall Maxima for Central and South Florida presents 24 hour s maximum rainfall data for 2 year, 50 year and 100 year return periods are 5 inches, 17.8 inches and 21 inches ( Pathak, 2001 ) Figure 3 2 R ainfall data from 1 /1/200 1 to 12 /3 1 /2006 Table 3 1 A verag e evaporation rate during January to December in 2006 Monthly evaporation (in/day) Jan Feb Mar Apr May Jun 0.16 0.19 0.24 0.3 0.29 0.26 Jul Aug Sep Oct Nov Dec 0.26 0.25 0.22 0.21 0.17 0.16

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35 Figure 3 3 100 year design storm Scenario Design To evaluate the effectiveness of LID and the impacts of building spatial pattern on LID practices, the site was designed and modeled using continuous simulation under four scenarios. Figure. 3 4 shows the schematic o f spatial pattern of these four scenarios. Pre development. This scenario is used as a basic scenario to examine the effectiveness of LID strategies in water. Although the site is already developed into a high density apartment, a pre development scenarios can be built based on the surrounding environment. Existing site plan (Without LID strategies). This model is built based on the actual situation. The neighborhood is consisted with 5 three story buildings and a bungalow with a swimming pool used as comm unity club. These building foot print combining with

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36 parking lots and roads consist the impervious surface which is 4.67 acre. This model is built to check the impact of high density house are in natural drainage system. LID site plan L. This is an advance d model built based on the existing site plan using LID strategies including green roof, rain garden, permeable pavement and bioswales. This scenario is created to examine the effectiveness of LID strategies used in high density residential area with lower rate of building footprint. LID site plan H. This plan cuts down the building footprint by raising the building levels in LID site plan L. In the meantime, the area of pervious surface is increasing. LID strategies such as green roof, rain garden, permea ble pavement and bioswales are also applied in this plan, but with different location and scale due to the change of the building spatial pattern.

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37 Figure 3 4 T he schematic of spatial pattern of four sc enarios

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38 CHARPTER 4 SCENARIOS DEVELOPMENT LID Strategies Design The infiltration methods can be classified into whole infiltration and partial infiltration. Differ from whole infiltration method using a subcatchment for permeating all the inflows, partial infiltrati on method adds nods under LID strategies to route water from the base storages. The whole infiltration method is used in the present study. Non Directly Connected Impervious Areas (NDCIA) for the subcatchment with NDCIA. The model will then flow runoff from the impervious area onto the pervious area. This method can be used to represent roof down spouts and patios draining over grass yards, and sidewalks draining to grassed areas, as seen in Figure. Parameters of LID control methods in SWMM In SWMM, parameters for settling LID control methods are classified into six categories including surface layer, pavement layer, soil layer, storage layer drain system, and drainage mat. Table 4 1 show s detailed categories of each LID strategy. Since LID site plans in this study applies the whole infiltration method, the drain system and drainage mat are not discussed. Table 4 1 Layers consist of LID stra tegies in SWMM LID Strategy Surface Pavement Soil Storage Drainage Mat Drain Rain Garden Green Roof v Permeable Pavement Bioswale

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39 Surface layer. Surface layer contains berm height, vegetation volume fraction, surface roughness, surface slope parameters and swale side slope parameter especially for bioswal es. Berm Height (or Storage Depth). This parameter describes the maximum depth of berm which used to contain water on the surface of LID control methods such as rain garden and permeable pavement when overflow happens. The general storage depth for rain g arden is 4 to 8 inches, since shallow rain garden need to be expanded to provide enough water storage and deep rain garden takes too long to drain. ( Bannerman & Considine, 2003 ) depth and for bioswales it is the height of the trapezoidal cross section. Vegetation Volum to volume of surface storage. In most cases, this volume can be neglected. However, in high density vegetation area like Florida in this case, the volume can be as high as 0.1. Surface Rough ness. This parameter is decided by type and condition of surface materials. Suggested values are shown in table. According to the table, 0.014 is used in permeable pavement, 0.24 is used in bioswale and extensive green roof which is more suitable for resid ential area than intensive green roof discussed in 2.3.2, and 0.80 is used in rain garden in this case. Surface Slope. This parameter is concerned in design processes of green roof, permeable pavement and bioswale. According to a study about Quantifying th e effect of slope on extensive green roof stormwater retention, green roof demonstrate greatest in 2% slope. ( Getter, Rowe, & Andresen, 2007 ) Also, table shows slope ranges of typical extensive green roof. Hence 2% is used for slope of green roofs in following models. 2%

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40 Slope of pavement surface is recommended for good drainage in Florida Greenbook. ( TALLAHASSEE, 2002 ) Less than 2% is recommaned for bioswale surface slope in Storm Water Technology Fact Sheet Vegetated Swales of vegetative swale by EPA. ( EPA, 2002 ) In this case, the default 1% is applied in models. 0 is used for other types of LIDs. Swale Side Slope. Mo stly, swale side slope is bigger than 3/1 (run/rise) Swale side slope remains default as 5 in this case. Pavement layer. Pavement layer is located under surface layer in permeable pavement. Thickness. Two type permeable pavement are used in LID site plan. Porous Concrete is used for driveways with a thickness of 5 inch, and interlocking pavers are used in parking lot with a thickness of 3 inch. ( VDEQ, 2011 ) Void Ratio. This parameter is used to describe the volume of void space. For porous concrete and interlocking pavers, void ratio is relative to the stone type. According to a study about permeable pavement, stone ASTM D 448 No.57 stone which has a 0.4 void ratio is a good choice for both porous concrete and interlocking pavers. ( VDEQ, 2011 ) Impervious Surface Fraction. It describes the coverage of impervious pavement of total area. Since porous pavement is continuous in this case, 0 is used for impervious surface fraction. ( VDEQ, 2011 ) Permeability. Permeability is also decided by structure and material of the pavement. The design permeability of porous pavement is 5 in/hr, for interlocking pavemen t is 0.5 in/hr in this models. ( VD EQ, 2011 )

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41 Clogging Factor. Pavement clogging can be caused by sediment from runoff that filling the void spaces in permeable pavement, preventing runoff go through infiltration layer. In this model, default value 0 is used as clogging factor to ignore cl ogging. Soil layer. Soil layer is below surface and pavement layer. The main function of soil layer is purify and absorb runoff then infiltrate them to the base storage layer or surroundings subcatchments. Parameters in this category are as followed. Thic kness. The thickness of the soil layer which is under the surface and pavement layer. In most cases, the soil layer thickness of land based bioretention LID strategies such as rain garden is between 18 to 36 inches. In this case, 5 inches is chosen for gre en roofs. And 18 inches is used in rain gardens and permeable pavements. Porosity. The ratio of the volume of void space to total volume of soil. For sandy soil in this case, the porosity is 0.437. olume after the soil has been allowed to drain fully. Below this level, vertical drainage of water through the soil al volume for a well dried soil where only bound water remains (as a fraction). The moisture content of the soil cannot in/hr or mm/hr) 4.74 In/ hr. is used for sandy soil in this study. conductivity decreases with decreasing soil moisture content Conductivity slope for

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42 sandy soil is 5 based on MSDGC SWM Modeling Guidelines & Standards. ( MSDGC, 2013 ) ion along the wetting front (inches or mm). This is the same parameter as used in the Green Ampt infiltration y soil in the following models. Storage layer. layer used in bio retention cells, permeable pavement systems, and infiltration trenches as a bottom storage/drainage layer. It is also used to specify the height of a rain barrel (or the thickness of a gravel layer or the height of a rain barrel concrete and interlocking pavement used in driveways and parking lots is 6 in. ( CDT, 2014 ) Void Ratio. It describes the percentage of solids in the storage layer. Generally, 0.5 to 0.75 is used for gravel beds. Default 0.75 is applied in this case. Seepage Rate. This parameter des cribes the percentage of water which infiltrate into soil under storage layer. The rate is depended on the local soil type. Since the soil type in the study site is sandy, 4.74 in/hr is used as seepage rate. Clogging Factor. In this model, default value 0 is used as clog ging factor to ignore clogging. Parameters for LID controls in this study are shown in Table 4 2, 4 3, 4 4

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43 Table 4 2 Parameters of rain garden in SWMM Layer Properties Value Surface Berm H eight (in.) 4 Vegetation Volume Fraction 0.1 Surface Roughness 0.8 Surface Slope (percent) 1 Soil Thickness (in. ) 18 Porosity 0.437 Field Capacity 0.062 Wilting Point 0.024 Conductivity (in/hr) 4.74 Conductivity Slope 5 Suction Head (in .) 1.93 Table 4 3 Parameters of green roof in SWMM Layer Properties Value Surface Berm Height (in.) 4 Vegetation Volume Fraction 0.1 Surface Roughness 0.24 Surface Slope (percent) 2 Soil Thickness (i n. ) 5 Porosity 0.437 Field Capacity 0.062 Wilting Point 0.024 Conductivity (in/hr) 4.74 Conductivity Slope 5 Suction Head (in.) 1.93 Drainage Mat Thickness (in. ) 3 Void Fraction 0.5 Roughness 0.1

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44 Table 4 4 Parameters of permeable pavement in SWMM Layer Properties Value Surface Berm Height (in.) 0 Vegetation Volume Fraction 0.1 Surface Roughness 0.014 Surface Slope (percent) 1 Pavement Thickness (in.) 3(PP), 5(PICP) Void Rati o 0.4 Impervious Surface 0 Permeability (in/hr) 5(PP), 0.5(PICP) Clogging Factor 0 Soil Thickness (in.) 18 Porosity 0.437 Field Capacity 0.062 Wilting Point 0.024 Conductivity (in/hr) 4.74 Conductivity Slope 5 Suction Head (in.) 1.93 St orage Thickness (in.) 6 Void Ratio (Voids/Solids) 0.75 Seepage Rate (in/hr) 4.74 Clogging Factor 0 Drainage Mat Thickness (in.) 3 Void Fraction 0.5 Roughness 0.1 LID Scenario Design Pre development condition The pre development condition is de signed as a basic scenario which shows how natural drainage system works under single storm event and continuous rainfall condition. In SWMM, the whole site is described as a subcatchment unit. nd drainage system

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45 subcatchment attributes and infiltration type are set up showing in table. According to the analysis in chapter 3, the area is 7.34 acers and the slope is 0.5 %. As the site drains stormwater into the Royal Galdes Canal in the east, the width of overland flow path is design as 500ft which is the length of the field from west to east. The infiltration method used in this research is Green odeling infiltration assumes that a sharp wetting front exists in the soil column, separating soil with some l capillary suction along the the site is considered as a grassland According to the soil characteristics table suction head for sandy soil is 1.93 inch, conductivity is 4.74 in/hr, and initial deficit is 0.375. In addition, the impervious area is 100% of the site. ( USDA, 1986 ) Existing condition The existing scenario is created based on the real site condition. T he different between the pre development scenario and the existing scenario is the rate of impervious area. The impervious area of existing case includes driveways, parking lots and building site, which is 62% of the total area. The leaving pervious area i s considered as same as the grassland with sandy soil in predevelopment scenario. Hence the only difference parameter between the pre development scenario and the existing scenario is the rate of impervious area. The attributes are shown in table.

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46 Figur e 4 1 Existing site plan LID site plan condition There are two different LID scenarios in this study. Both sites have same amount of resident units guaranteeing these two plans have same population density. One of these LID plans is LID site plan L which adds LID strategies including green roof, rain garden, and permeable pavement on existing site plan without changing the building sites area. The other scenario LID plan H uses LID strategies as well, but the area of building sites are reduced by half as building levels are double from three to six. The area of LID strategies are different in these two LID plans due to the different spatial pattern. In LID plan L scenario, the design green roof covers 100% of the flat roof surfaces which area is 87426 ft2. However, when it comes to LID plan H, the roof area are decreased to 41287 ft2 which is 47% of that in LID plan L. As LID plan H reduces the building site area, there are more space available for rain gardens Hence, the area

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47 of rain gardens in LID plan H which is 11819 is ft2 is 70% larger than that in LID plan L which is 7040 ft2. According to the discussion in 2.3.1, places where sunny and directly drying the moisture infiltration soil layer and capturing runoff. So in both LID site plans, rain gardens are located around the building except the shadow north side. The other LID strategy used in LID site plan is permeable pavement. Based on the discus sion in section 2.3.3 and 2.4 two kind of permeable pavements are chosen to be applied, one is porous concrete used for driveways, and the other one is interlocking pavers used in parking lots. In this research, assuming the changing of building site has n o influence on area of driveways and parking lots since both LID plans has same population density.

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48 Figure 4 2 LID site plan L Figure 4 3 LID site pla n H

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49 CHARPTER 5 RESULTS AND DISCUSSION Comparing Pre development scenario and Existing site plan scenario Continuous model results The continuous PCSWMM model output are analyzed based on runoff volume, flow duration, and flood frequency for Pre development scenario and existing site plan scenario. Runoff volume Figure 5 1 presents the runoff of predevelopment scenario and existing site plan scenario under continuous 5 years. Table. 5 1 shows the total runoff volumes of five years. The runoff of the existing plan is much larger than the predevelopment scenario whose runoff is 0 throughout the simulation time span. Figure 5 1 Runoff of predevelopment scenario and existing site plan scenario under continuous 5 years

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50 Table 5 1 Runoff of predevelopment scenario and existing site plan scenario under continuous 5 years System ExsitingSitePlan Continuous5year System Predevelopment Continuous5year Maximum Runoff(cfs): 12. 7 0 Minimum Runoff(cfs): 0 0 Mean Runoff(cfs): 0.0288 0 Total Runoff(ft): 5450000 0 Single event model results Runoff volume The runoff of two scenarios are compared under 2 year, 50 year, and 100 year design storm. (Figure. 5 2, 5 3, 5 4) Similar to the five year continuous situation, f or 2 year design storm, the runoff of predevelopment scenario is 0 while the run off of existing site plan scenario is much higher. For 50 year and 100 year storm cases, the runoff of predevelopment is still much lesse r than existing site plan scenario but not remains 0 Under 100 year design storm, t he total runoff of existing plan is six times larger than that of the predevelopment one while the peak flow of existing plan is three times larger than that of the predev elopment one. Under 50 year design storm, the total runoff of existing plan is nine times larger than that of the predevelopment one while the peak flow of existing plan is six times larger than that of the predevelopment one. (Table 5 2) As a result, the existing plan largely reduce the ability to control runoff comparing with the predevelopment condition. For small precipitation, the predevelopment condition is more effective in controlling runoff. As the precipitation increases, the effectiveness of cont rolling runoff for predevelopment condition becomes less significant.

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51 Figure 5 2 Runoff of Existing site plan and Predevelopment under 2 year storm Figure 5 3 Runoff of Existing site plan and Predevelopment under 50 year storm

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52 Figure 5 4 Runoff of Existing site plan and Predevelopment under 100 year storm Table 5 2 Runoff Existing site plan and Predevelopment in single events Predevelopment Exsiting Site Plan 2 Year 50 Year 100 Year 2 Year 50 Year 100 Year Maximum Runoff (cfs) 0 11.73 19.16 13.96 57.56 70.04 Minimum Runoff (cfs) 0 0 0 0.008348 0.07195 0.0 9331 Mean Runoff (cfs) 0 0.3397 0.5883 0.8953 3.537 4.265 Total Runoff (ft) 0 29040 50300 76550 302400 364600 Comparing Existing site plan scenario and LID site plan L scenario Continuous model results The simulation result of existing site plan scena rio and LID site plan L scenario under continuous rainfall condition are compared in this section.

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53 Runoff volume The runoff of existing site plan scenario and LID site plan L scenario under continuous rainfall condition are compared in this section. Figure .5 5 shows the runoff during five years of both scenarios. The total volume of runoff for existing site plan scenario is much higher than that for LID site plan L And d uring small precipitation period the LID site plan controls runoff better than existin g site plan However, the Table. 5 3 shows that the peak of r unoff in both scenario is close. Figure 5 5 Runoff summary of LID site plan L and Existing site plan through 2001 to 2006

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54 Exceedances The exc eedances includes duration hours and numbers of exceedances. T he exceedances hours refers to total hours when runoff volume exceeds 0.02 cfs ( cubic feet per second ). And the exceedances number represents the number of peaks that exceeds 0.02 cfs. These par ameters are calculated u sing Pc T able. 5 3 shows that the number of exceedances are close of both scenarios. However, the duration of exceedances hours for existing site are 50% higher than that for LID site plan L. Table 5 3 Exceedances analysis of LID site plan L and Existing site plan (Exceedance threshold=0.02 cfs) Ex is tingSitePlan Continuous5year LIDSitePlanL Continuous5year Maximum Runoff(cfs): 12.7 11.96 Minimum Runoff(cfs): 0 0 Mean Runoff(cfs): 0.0288 0.01222 Duration of Exceedances(h): 2533 1760 Number of Exceedances: 897 876 Volume of Exceedances(ft): 5239000 2158000 Volume of Deficits(ft): 0 0 Total Runoff(ft): 5450000 2312000 Annual peak volume The annual peak volume is calculated using PCSWMM frequency analysis on annual time series. Plotting position formulas is Gringorten. For the whole range of return period, the peak runoff of LID site plan L is smaller than that of existing site plan. In addition, for retu rn period smaller than 2.4 years, the LID site plan L control the runoff

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55 much more efficiently than the existing site plan, while for return period larger than 2.4 years, the above difference become less significant. (Figure. 5 6) Figure 5 6 Frequency analysis of event volume of Lid site plan L and Existing site plan LID practices performance In order to estimate the runoff control ability of different LID practice. Green roof, rain garden and permeable pav ement of LID site plan L are modeling individually under 5 year continuous rainfall time series. Table. 5 4 shows that permeable pavement has the lowest peak runoff and smallest total runoff, which makes it the best runoff control strategy in LID site pla n L. As for total runoff, the total runoff of green roof is lesser than that of rain garden. It means the green roof has a better ability of reducing runoff. As for maximum runoff, the maximum runoff of green roof is larger than rain garden. It means that the rain garden has a better ability of controlling peak flow. 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 Peak runoff (cfs) Return period (year) LID site plan L Existing Site Plan

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56 Table 5 4 Runoff summary of g reen roof, rain garden and permeable model GreenRoof PermeablePavement Raingarden Maximum Runoff(cfs): 14.85 10. 09 12.41 Minimum Runoff(cfs): 0 0 0 Mean Runoff(cfs): 0.02317 0.01853 0.02827 Total Runoff(ft): 4385000 3507000 5350000 Single event model results The runoff of existing site plan scenario and LID site plan L scenario are compared under 2 year, 50 y ear, and 100 year design storm. (Figure. 5 7, 5 8, 5 9 ). Table. 5 5 presents the runoff volume for these two scenario under different design storms. F or 2 year design storm, the difference between two scenarios is significant. The maximum runoff volume of existing site plan scenario is as much as twice that value of LID site plan L. And f or 50 year and 100 year storm cases, the total runoff of existing plan is 10% larger than that of the LID site plan L scenario. However, when the precipitation is large, th e peak runoff of LID site plan L is large than existing site plan. Because when in the early period of precipitation LID site plan L is saturated due to infiltration a lot of runoff, so the continuous runoff cannot be absorbed efficiently. As a result, fo r smaller precipitation the LID site plan L can largely reduce the total runoff and peak flow comparing with the existing plan. However, for large precipitation, the ability of reducing total runoff for LID site plan L is decreasing and the LID site plan L cannot control the peak discharge well.

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57 Figure 5 7 Runoff of Existing site plan and LID site plan L under 2 year storm Figure 5 8 Runoff of Existing s ite plan and LID site plan L under 50 year storm

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58 Figure 5 9 Runoff of Existing site plan and LID site plan L under 100 year storm Table 5 5 Runoff summary of Existing site plan and LID site plan L in single events Existing Site Plan LID Site Plan L 2 Year 50 Year 100 Year 2 Year 50 Year 100 Year Maximum Runoff(cfs): 13.96 57.56 70.04 4.815 65.86 80.43 Minimum Runoff(cfs): 1.1 4.192 4.985 0.3824 1.422 1.68 7 Mean Runoff(cfs): 4.238 16.88 20.57 1.489 14.97 18.58 Total Runoff(ft): 45290 180400 219800 15920 160000 198600

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59 Comparing LID site plan L scenario and LID site plan H scenario Continuous model results Runoff volume The runoff of LID site plan H s cenario and LID site plan L scenario under continuous rainfall condition are compared in this section. Figure.5 10 shows the runoff during five years of both scenarios. Table. 5 6 shows that t he total volume of runoff for LID site plan L is much higher tha n that for LID site plan L. And during large precipitation period, the LID site plan controls runoff better than existing site plan. Figure 5 10 Runoff summary of LID site plan L and LID site plan H throug h 2001 to 2006

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60 Table 5 6 Runoff of LID site plan L and LID site plan H under continuous 5 years Exceedances The exceedances includes duration hours and numbers of exceedances. T he exceedances hours refers to total hours when runoff volume exceeds 0.0 1 cfs which is the approximate value of mean runoff And the exceedances number represents the number of peaks that exceeds 0.0 1 cfs. Table. 5 7 shows that the duration, number and total volume of exceedanc es are close of both scenarios. However, the duration and number of exceedances for LID site plan H is higher than LID site plan L, while LID site plan L has a larger total volume of exceedances. From the total exceedances runoff volume point of view, LID site plan H has a better ability to control runoff. As for the long er duration time of each peak for LID site plan H, it means that the retain time is longer. As for the larger number of exceedances of LID site plan H, it means that the ability of runoff control is less effective than that of LID site plan L during small precipitation. LIDSitePlanH Continuous5year LIDSitePlanL Continuous5year Maximum Runoff(cfs): 9.306 11.96 Minimum Runoff(c fs): 0 0 Mean Runoff(cfs): 0.01176 0.01222 Total Runoff(ft): 2225000 2312000

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61 Table 5 7 Exceedances analysis of LID site plan H and LID site plan L ( Exceedance threshold =0.01 cfs) LIDSitePlanH Continuous5year LIDSitePlanL Continuous5year Duration of Exceedances(h): 1 124 1112 Number of Exceedances: 747 739 Volume of Exceedances(ft): 1686000 1766000 Annual peak volume The annual peak volume is calculated using PCSWMM frequency analysis on annual time series. Plotting position formulas is Gringorten. For the whole r ange of return period, the peak runoff of LID site plan H is smaller than that of LID site plan L (Figure. 5 11 ) It indicates that the ability of peak flow control for LID site plan H is better than that for LID site plan L.

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62 Figure 5 11 Frequency analysis of event volume of Lid site plan L and LID site plan H Single event model results Runoff volume The runoff of LID site plan H and LID site plan L scenario are compared under 2 year, 50 year, and 100 y ear design storm. (Figure. 5 1 2 5 1 3 5 1 4 ). Table. 5 8 presents the runoff volume for these two scenario under different design storms. For 2 year design storm, the total runoff of LID site plan H is higher than LID site plan L. The peak rate of LID site plan H scenario is 7% more than that value of LID site plan L. However, for 50 year and 100 year storm cases, the total runoff of LID site plan L is larger than that of the LID site plan H scenario. And under 50 year, the peak discharge of LID site plan L 17% larger than that of the LID site plan H. When it comes to 100 year storm cases the peak discharge of LID site plan L is 15% larger than that of the LID site 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 Peak runoff (cfs) Return period (year) LID site plan H LID site plan L

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63 plan H As a result, for smaller precipitation the LID site plan L can reduce the total runof f and peak flow more efficiently comparing with the LID site plan H However, for large precipitation, the ability of reducing total runoff for LID site plan H is better than LID site plan L. Figure 5 12 R unoff of LID site plan L and LID site plan H under 2 year storm

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64 Figure 5 13 Runoff of LID site plan L and LID site plan H under 50 year storm Figure 5 14 Runoff of LID site plan L and LID site plan H under 100 year storm

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65 Table 5 8 Runoff summary of LID site plan L and LID site plan H in single events LID Site Plan L LID Site Plan H 2 Year 50 Year 100 Year 2 Year 50 Year 100 Year Maximum Runoff(cfs): 4.815 65.86 80.43 5.198 56.21 69.66 Minimum Runoff(cfs): 0.006713 0.04662 0.05848 0.0033 01 0.02338 0.0296 Mean Runoff(cfs): 0.3074 2.762 3.389 0.3308 2.418 3.02 Total Runoff(ft): 26290 236100 289700 28280 20 6700 258200 Conclusion The results of c omparing Pre development scenario and Existing site plan scenario indicate that high density house can significantly increase the stormwater runoff. The results of c omparing Existing site plan scenario and LID sit e plan L scenario present that LID strategies works more efficiently under small precipitation. And Permeable pavement is the most efficient Lid strategy in controlling runoff. Comparing with green roof, rain garden has a better a bility of controlling peak flow but are less effective in reducing total runoff. Synthesizing evaluation of LID strategies in different aspects which is discussed in section 2.4, permeable pavement is cheap but the need frequent maintenance. G reen roofs is expensive but need less m aintenance, also it has the best cost efficiency in runoff reduction Rain garden has the modest performance in cost and maintenance, but it can efficiently reducing runoff pollution. As runoff pollution issue is significant in high density area, rain gard en which can efficiently reducing the pollution and with modest performance in other aspects is recommended to applying to high density residential area. But as how to leave enough space and combine the landscape with the design of rain gardens is need to be concern. Besides, permeable

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66 pavement which is the highest in feasibility is also recommended to high density area. I f economic is possible green roof is also a good choice to high density area since it not occupy ground space and has the best cost eff iciency in runoff reduction. The results of c omparing LID site plan L scenario and LID site plan H scenario shows that for smaller precipitation the LID site plan L can reduce the total runoff and peak flow more efficiently comparing with the LID site plan H. However, for large precipitation, the ability of reducing total runoff for LID site plan H is better than LID site plan L. Comparing the runoff reduction effectiveness of LID strategies used in high density residential area with different spatial patte rn And the ability of peak flow control for LID site plan H is better than that for LID site plan L. As conclusion even site plan which is represented by LID site L is more suitable for residential area where precipitation is smaller. And the concentrated site plan which is represented by Lid site plan H is more suitable for residential area where precipitation is larger.

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67 LIST OF REFERENCES ABC. (2015). FLOODING / SEA LEVEL RISE STORMWATER MANAGEMENT. Retrieved 07/02, 2015, from http://challengeforsustainability.org/ Ahiablame, L. M., Engel, B. A., & Chaubey, I. (2012). Effectiveness of Low Impact Development Practices: Literature Review and Suggestions for Future Research. Wat er Air and Soil Pollution, 223 (7), 4253 4273. Bannerman, R. T., & Considine, E. (2003). Rain Gardens: A how to manual for homeowners : Wisconsin Department of Natural Resources. Bengtsson, L., Grahn, L., & Olsson, J. (2005). Hydrological function of a thin extensive green roof in southern Sweden. Nordic Hydrology, 36 (3), 259 268. Berndtsson, J. C. (2010). Green roof performance towards management of runoff water quantity and quality: A review. Ecological Engineering, 36 (4), 351 360. doi: DOI 10.1016/j.ecol eng.2009.12.014 Bowman, T., Tyndall, J. C., Thompson, J., Kliebenstein, J., & Colletti, J. P. (2012). Multiple approaches to valuation of conservation design and low impact development features in residential subdivisions. J Environ Manage, 104 101 113. d oi: 10.1016/j.jenvman.2012.02.006 Carlson, W., Fitzpatrick, E., Flanagan, E., Kirschbaum, R., Williams, H., & Zickler, L. (2013). Eastern Washington Low Impact Development Guidance Manual. CDT, C. D. o. T. (2014). Pervious Pavement Design Guidance. Clark, Florida Field Guide to Low Impact Development Collett, B., McCown, K., & Wall, S. (2013). LOW IMPACT DEVELOPMENT OPPORTUNITIES FOR THE PlanET REGION. Davis, A. P. (2008). Field performance of biorete ntion: Hydrology impacts. Journal of Hydrologic Engineering, 13 (2), 90 95. Dietz, M. E. (2007). Low impact development practices: A review of current research and recommendations for future directions. Water, air, and soil pollution, 186 (1 4), 351 363. E PA. (2000). Low Impact Development (LID) A Literature Review EPA. (2002). Storm Water Technology Fact Sheet Vegetated Swales. Fassman, E. A., & Blackbourn, S. (2010). Urban runoff mitigation by a permeable pavement system over impermeable soils. Journa l of Hydrologic Engineering Ferguson, B. K. (2005). Porous Pavements Boca Raton, FL: CRC Press. Getter, K. L., Rowe, D. B., & Andresen, J. A. (2007). Quantifying the effect of slope on extensive green roof stormwater retention. Ecological Engineering, 3 1 (4), 225 231. Jia, H., Lu, Y., Shaw, L. Y., & Chen, Y. (2012). Planning of LID BMPs for urban runoff control: The case of Beijing Olympic Village. Separation and Purification Technology, 84 112 119. Joksimovic, D., & Alam, Z. (2014). Cost Efficiency of Low Impact Development (LID) Stormwater Management Practices. Procedia Engineering, 89 734 741. Mangarella, P., & Palhegyi, G. (2002). Santa Clara Valley Urban Runoff Pollution Prevention Program: Hydromodification Management Plan Literature Review. Geo Syntec Consultants, Walnut Creek, CA Mentens, J., Raes, D., & Hermy, M. (2006). Green roofs as a tool for solving the rainwater runoff problem in the urbanized 21st century? Landscape and Urban Planning, 77 (3), 217 226. doi: DOI 10.1016/j.landurbplan.200 5.02.010 MSDGC, T. M. S. D. o. G. C. (2013). MSDGC MODELING GUIDELINES AND STANDARDS VOLUME I SYSTEM WIDE MODEL. Pathak, C. S. (2001). Frequency analysis of daily rainfall maxima for Central and South Florida : Hydro Information Systems & Assessment Depart ment, South Florida Water Management District.

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68 Resnik, D. B. (2010). Urban sprawl, smart growth, and deliberative democracy. Am J Public Health, 100 (10), 1852 1856. doi: 10.2105/AJPH.2009.182501 Takebayashi, H., & Moriyama, M. (2007). Surface heat budget o n green roof and high reflection roof for mitigation of urban heat island. Building and Environment, 42 (8), 2971 2979. doi: DOI 10.1016/j.buildenv.2006.06.017 TALLAHASSEE, F. (2002). MANUAL OF UNIFORM MINIMUM STAN DARDS FOR DESIGN, CONSTRUCTION AND MAINTENANCE FOR STREETS AND HIGHWAYS. USDA, S. (1986). Urban hydrology for small watersheds. Technical release, 55 2 6. VDEQ, V. D. o. E. Q. (2011). VIRGINIA DEQ STORMWATER DESIGN SPECIFICATION No. 7. from http://www.vwrrc.vt.edu/swc/NonPBMPSpecsMarch11/VASWMBMPSpec7PERMEABLEPAVEME NT.html Virginia, D. (2010a). Stormwater Design Specification No. 10. Infiltration Practices Version, 1 Virginia, D. (2010b). Stormwater Design Specification No. 11. Infiltration Practices Version, 1 Wang, R., Eckelman, M. J., & Zimmerman, J. B. (2013). Consequential environmental and economic life cycle assessment of green and gray stormwate r infrastructures for combined sewer systems. Environ Sci Technol, 47 (19), 11189 11198. doi: 10.1021/es4026547 William F. Hunt, I., & Bean, E. Z. (2006). NC STATE UNIVERSITY PERMEABLE PAVEMENT RESEARCH AND CHANGES TO THE STATE OF NC RUNOFF CREDIT SYSTEM W WAP. (2015). The United Nations World Water Development Report 2015.


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