Citation
Hurricane Opal

Material Information

Title:
Hurricane Opal results from repeated surveys in selected developed and undeveloped areas
Series Title:
UFLCOEL-98020
Creator:
Dean, Robert G ( Robert George ), 1930-
Suter, Carrie L
University of Florida -- Coastal and Oceanographic Engineering Dept
Florida -- Office of Beaches and Coastal Systems
Place of Publication:
Gainesville Fla
Publisher:
Coastal & Oceanographic Engineering Program, Dept. of Civil & Coastal Engineering, University of Florida
Publication Date:
Language:
English
Physical Description:
1 v. (various foliations) : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Hurricane Opal, 1995 ( lcsh )
Coast changes -- Florida -- Florida Panhandle ( lcsh )
Hurricanes -- Environmental aspects -- Florida -- Florida Panhandle ( lcsh )
Storm surges -- Environmental aspects -- Florida -- Florida Panhandle ( lcsh )
Genre:
government publication (state, provincial, terriorial, dependent) ( marcgt )
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references.
General Note:
"December 28, 1998."
General Note:
"Project sponsor: Bureau of Beaches and Coastal Systems, Department of Environmental Protection."
Statement of Responsibility:
prepared by Robert G. Dean and Carrie L. Suter.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
43794608 ( OCLC )

Full Text
UFL/COEL-98/020

HURRICANE OPAL RESULTS FROM REPEATED SURVEYS IN SELECTED DEVELOPED AND UNDEVELOPED AREAS
by
Robert G. Dean and
Carrie L. Suter

December 28, 1998
Project Sponsor: Bureau of Beaches and Coastal Systems Department of Environmental Protection Tallahassee, Florida 32399-3000




HURRICANE OPAL

RESULTS FROM REPEATED SURVEYS IN SELECTED
DEVELOPED AND UNDEVELOPED AREAS
December 28, 1998
Prepared by: Robert G. Dean and
Carrie L. Suter
Project Sponsor: Bureau of Beaches and Coastal Systems Department of Environmental Protection Tallahassee, Florida 32399-3000
Submitted by: Department of Coastal and Oceanographic Engineering University of Florida Gainesville, Florida 32611




TABLE OF CONTENTS
LIST OF FIGU RES ........................................................... iii
LIST OF TABLES ............................................................ A
1 INTRODU CTION ....................................................... 1
1.1 Purpose .......................................................... 1
1.2 B ackground ...................................................... 2
2. MONITORING EFFORTS BY THE UNIVERSITY OF FLORIDA ................ 3
3. R ESU LTS ............................................................. 3
3.1 Beach Profiles .................................................... 3
3.2 Beach Volumes and W idths .......................................... 5
3.3 D une Recovery ................................................... 11
4. D ISCU SSION ......................................................... 11
5. EFFECT OF FEBRUARY 1998 SURVEY ................................... 19
6. CONCLUSION S ....................................................... 20
7. REFEREN CES ........................................................ 20
APPENDICES
A DESCRIPTION OF METHODOLOGY USED FOR COMPUTATIONS OF
AVERA GES ........................................................ A -1
B PLOTS OF SHORELINE AND VOLUME CHANGES ....................... B-1




LIST OF FIGURES

FIGURE PAGE
1 Location M ap of Four Study Sites ........................................... 1
2. Beach Profile in Natural Area of Santa Rosa County, Monument Number R-188 ...... 4 3. Cumulative Change in Average Volume for All Escambia County Profiles ........... 7
4. Beach Profile R-194.5 in Developed Area of Santa Rosa County Showing
Artificially Placed Berm .................................................. 9
5. Cumulative Change in Average Volume for All Counties ....................... 13
6, Cumulative Change in Average Volume for All Developed Profiles ............... 14
7. Cumulative Change in Average Volume for All Natural Profiles .................. 15
8. Cumulative Change in Average Shoreline Position for All Counties. Pre-Opal
and October 1995 Positions Based on Aerial Photography ....................... 16
9. Cumulative Change in Average Shoreline Position Line for All Developed
Profiles. Pre-Opal and Oct 1995 Positions Based on Aerial Photographs ............ 17
10. Cumulative Change in Average Shoreline Position for All Natural Profiles. PreOpal and Oct 1995 Positions Based on Aerial Photographs ...................... 18
B-1. Cumulative Change in Average Volume for All Counties ...................... B-2
B-2. Cumulative Change in Average Volume for All Developed Profiles .............. B-3
B-3. Cumulative Change in Average Volume for All Natural Profiles ................. B-4
B-4. Cumulative Change in Average Shoreline Position for All Counties. Pre-Opal and
October 1995 Positions Based on Aerial Photography ......................... B-5
B-5. Cumulative Change in Average Shoreline Position for All Developed Profiles.
Pre-Opal and Oct 1995 Positions Based on Aerial Photographs .................. B-6
B-6. Cumulative Change in Average Shoreline Position for All Natural Profiles. PreOpal and Oct 1995 Positions Based on Aerial Photographs ..................... B-7




B-7. Cumulative Change in Average Volume for All Escambia County Profiles ......... B-8
B-8. Cumulative Change in Average Volume for Developed Profiles in Escambia
C ounty .............................................................. B -9
B-9. Cumulative Change in Average Volume for Natural Profiles in Escambia County ..1B-10 B-10. Cumulative Change in Average Shoreline Position for All Escambia County
Profiles. March '84 and Oct '95 Positions Based on Aerial Photographs .......... B-11
B-1 1. Cumulative Change in Average Shoreline Position for Developed Profiles.
Escambia County. Mar '84 and Oct '95 Positions Based on Aerial Photographs .... B-12 B-12. Cumulative Change in Average Shoreline Position for Natural Profiles. Escambia
County. Mar '84 and Oct '95 Positions Based on Aerial Photographs ............. B-13
B-13. Cumulative Change in Average Volume for All Santa Rosa County Profiles ...... B-14 B-14. Cumulative Change in Average Volume for Developed Profiles in Santa Rosa
C ounty ............................................................. B -15
B-15. Cumulative Change in Average Volume for Natural Profiles in Santa Rosa
C ounty ............................................................. B -16
B-16. Cumulative Change in Average Shoreline Position for All Santa Rosa County
Profiles. March '84 and Oct '95 Positions Based on Aerial Photographs .......... B-17
B-17. Cumulative Change in Average Shoreline Position for Developed Profiles in
Santa Rosa County. Mar'84 and Oct '95 Positions Based on Aerial Photographs ... B-18 B-18. Cumulative Change in Average Shoreline Position for Natural Profiles in Santa
Rosa County. Mar '84 and Oct '95 Positions Based on Aerial Photographs ........ B-19 B-19. Cumulative Change in Average Volume for All Walton County Profiles ......... B-20
B-20. Cumulative Change in Average Volume for Developed Profiles in Walton County B-21 B-21 Cumulative Change in Average Volume for Natural Profiles in Walton County .... B-22 B-22. Cumulative Change in Shoreline Position for All Walton County Profiles. Oct
1995 Positions Based on Aerial Photographs ............................... B-23
B-23. Cumulative Change in Shoreline Position for Developed Profiles in Walton
County. Oct '95 Positions Based on Aerial Photographs ....................... B-24




B-24. Cumulative Change in Shoreline Positions for Natural Profiles in Walton County.
Oct'95 Positions Based on Aerial Photographs .............................. B-25
B-25. Cumulative Change in Average Volume for All Bay County Profiles ............ B-26
B-26. Cumulative Change in Average Volume for Developed Profiles in Bay County .... B-27 B-27. Cumulative Change in Average Volume for Natural Profiles in Bay County ....... B-28 B-28. Cumulative Change in Average Shoreline Position for All Bay County Profiles.
Oct 1995 Positions Based on Aerial Photography ............................ B-29
B-29. Cumulative Change in Shoreline Position for Developed Shorelines in Bay
County. Oct 1995 Positions Based on Aerial Photography ..................... B-30
B-30. Cumulative Change in Average Shoreline Position for Natural Profiles for Bay
C ounty .............................................................. B -31




LIST OF TABLES

TABLE PAGE
I DNR Monument Numbers for "Developed" and "Natural Areas Monitored by
C O E .................................................................. 3
2. Average Shoreline Changes: Pre-Opal to Immediately Post-Opal and Post-Opal to
First COE Survey in M ay 1996 ............................................ 10
3. Beach Volume and Width Trends as Determined by the Least Squares Method ...... 12 A-1 Original Shoreline Positions ............................................ A-1
A-2 Shoreline Changes from Original Positions ................................. A-2
A-3 Shoreline Changes from Original Positions, with Average Shoreline Change ...... A-2 A-4 Complete Data Set for Shoreline Changes with Average Shoreline Change Filled
in all Em pty Data Sets ................................................. A-2
A-5 Complete Data Set for Original Shoreline Positions .......................... A-3
A-6 Shoreline Position Changes ............................................. A-4




HURRICANE OPAL
RESULTS FROM REPEATED SURVEYS IN SELECTED DEVELOPED AND UNDEVELOPED AREAS
1. INTRODUCTION
1.1 Purpose
This report presents the results of an intensive two year monitoring study conducted in the wake of Hurricanes Erin and Opal by the University of Florida's Department of Coastal and Oceanographic Engineering (COE). Four specific shorelines sites, each including both developed and natural areas in the Panhandle of Florida, were surveyed from May 1996 to February 1998. In total, five surveys from the COE and several surveys and aerial photographs available from the Florida Bureau of Beaches and Coastal Systems (BBCS) of the Florida Department of Environmental Protection (DEP) provide the basis for both volumetric and beach width changes in the following counties from west to east: Escambia, Santa Rosa, Walton and Bay, see Figure 1.

3390000 3370000 3350000 3330000 3310000 3290000

3270000 -t 1 1
450000 470000 490000

510000 530000 550000 570000 590000 610000 630000 650000
EASTING (m,. UTM Zone 16, NAD 1983)

Figure 1. Location Map of Four Study Sites.




1.2 Background

On October 4, 1995 at approximately 6:00 p.m. Central Daylight Time, Hurricane Opal made landfall near Navarre Beach, which is located on Santa Rosa Island in Santa Rosa County. Prior to Hurricane Opal, Hurricane Erin had impacted the Florida Panhandle on August 3, 1995. In the most active storm season since 1933, Hurricane Opal was the 15th named storm out of 21 total tropical storms or hurricanes. At landfall, the winds decreased to 110 mph from the maximum sustained surface winds of 150 mph, which had placed the hurricane at a Category 4 status on the SaffirSimpson scale. As determined by the Beaches and Shores Resource Center of Florida State University, the hurricane had a central pressure deficit of 2.16 in. mercury, a radius of maximum winds estimated at approximately 30 miles and a forward speed of 23 knots in a north-northeast direction (Leadon, 1996).
Storm surge data obtained from a National Oceanic and Atmospheric Agency (NOAA) tide gauge located on the Panama City Beach pier showed a peak water level of 8.3 feet above National Geodetic Vertical Datum (NGVD), which was nearly 8 feet above the normal predicted astronomical tide. High water mark surveys conducted by DEP staff documented a storm surge ranging from 8-11 feet above NGVD between Pensacola Beach and Fort Walton Beach and approximately 12-20 feet above NGVD between Destin and Seagrove Beach (FEMA, 1996). In Panama City Beach, evidence of wave impacts and sand deposition were found in first-floors of structures up to 17-18 feet above NGVD during post-storm inspections conducted by the DEP (Leadon, 1996).
Hurricane Opal caused extensive damage to the beach and dune system. Eight million cubic yards of sand were lost from above sea level due to breaking waves, extensive flooding, a substantial storm surge and extensive overwash in lower dune areas. East of Fort Walton Beach, portions of Highway 98 were washed away, and many of the survey control monuments maintained by the BBCS were destroyed (Leadon, 1996). The approximately $2 billion damage to structures during Hurricane Opal rank it as one of the most costly natural disasters to affect the United States (FEMA, 1996). It caused more structural damage along the Florida coast than all of the hurricanes and tropical storms combined in the last 20 years (Leadon, 1996).
Immediate post storm response consisted mainly of debris removal and beach scraping, the bulldozing of sand from the lower portions of the subaerial profile and moving this sand landward to the base of an eroded dune. Because the navigational entrance to St. Andrews Bay at the eastern limit of Panama City Beach places erosional pressure on the shoreline of Panama City Beach, renourishment of this beach is in progress and improved management of the sand resources in the vicinity of the entrance is being investigated.




2. MONITORING EFFORTS BY THE UNIVERSITY OF FLORIDA

The five monitoring surveys conducted by the COE took place in: May 1996, October 1996, March 1997, July 1997 and February 1998. The four areas surveyed in Escambia, Santa Rosa, Walton and Bay Counties each contained approximately 20 survey monuments and each county area contained approximately equal lengths of "developed" and "natural" shorelines. The monuments were located approximately 500 feet apart, and the surveys were carried out with standard land-based rod and level survey techniques with the surveying planned to extend from the monuments out to wading depth limits. An area was deemed "natural" if there were no structures located in the immediate vicinity of the monument and "developed" if there were. Walton County was the one exception to this definition, as the entire study area was situated in a local city. Therefore, Henderson State Park and four other monuments in Walton County were included in the "natural" category, even though they would not normally be considered "natural", due to a parking lot adjacent to the beach. This segment was considered natural due to the protection and vegetation of the dunes from the parking lot down to the beach berm.
Table 1 presents the locations of the "developed" and "natural" areas, identified by their corresponding BBCS monument numbers.
Table 1
DNR Monument Numbers for "Developed" and "Natural" Areas Monitored by COB
County "Developed" "Natural"~
Escambia R133 to R138.5 R139 to R144
Santa Rosa R1 92.5 to R197 R187 to R192
Walton R1 to R2, R4.5 to R6A.5 R2.5 to R4, R7 to R8.5
Bay R85 to R91, R93 R91.5 to R97 (excetnt R23)
3. RESULTS
3.1 Beach Profiles
The survey data were plotted for each monument and computer programs were developed and applied to extract shoreline and volumetric changes from the data. A typical profile for the natural areas of Santa Rosa County is plotted in Figure 2 for Monument Number R-1 88. By plotting several surveys on the same graph, erosional or accretional trends are evident. To better illustrate




20 ........I March 1997
February 1998
~15
-~ 0c10 Jl19
0 Gulf of Mexico
0 100 200 300 400 500
Distance Seaward of Monument (ft)
Figure 2. Beach Profile in Natural Area of Santa Rosa County, Monument Number R-188.




these trends, the profile at Santa Rosa County Monument R- 188 will be discussed in detail.
The monument location is plotted as zero on the horizontal axis, and all subsequent horizontal positions are relative to the monument position. At this particular location in Santa Rosa County, the dune system is extensive, as indicated by the 17 foot height of the primary dunes. The dune heights in this area decrease with increasing proximity to the developed areas, which are located 5,000 feet farther east. The solid line plotted on the graph represents the only DEP survey (February 1996) used in the Santa Rosa County analysis. The survey was conducted 4 months after Hurricane Opal and illustrates several storm effects. The very steep dune scarp with the distinct cut at the base is a result of hurricane waves impacting this dune. Each subsequent survey shows an increasingly milder slope of the dune scarp, probably due to sloughing of the sediments to approach a more natural angle of repose, i.e. the steepest angle that a loose sediment of a given size can remain stable.
The seasonal fluctuations are most evident in the vicinity of the beach face, which is located approximately 180-260 feet from Monument R-188 at the gulfward limit of the berm. For those surveys that would typically be considered "summer" profiles, the October 1996 and July 1997 surveys, the beachface locations are more landward than for the other surveys, thus resulting in a narrower beach for the summer surveys. Two of the winter profiles, (May 1996 and March 1997) consist of somewhat wider beaches with larger volumes. This is contrary to the normal definition of "summer" and "winter" profiles normally associated with sandy beaches.
The February 1998 survey was conducted immediately after two storms impacted the area. The narrowed beach width, a steep scarp in the vicinity of the high water lines of the storms (located at approximately 220 feet) and an offshore bar are all signs of a post-storm beach. The sand in the offshore bar was eroded from the beach face during the storm, but will most likely be redeposited back on the beach during periods of milder wave activity.
Due to the different tide and wave conditions during the various surveys, each survey ends at a different distance from the monument. For example, the DEP survey was conducted farther offshore than any of the COB surveys which were planned to extend to wading depth only. The volumetric computations were extended out to the seawardmost common surveyed point at the monument location for all surveys. For Monument Number R- 18 8 in Santa Rosa County, the last data point for the July 1997 survey establishes the limiting distance for volumetric computations and is approximately 250 feet from the monument.
3.2 Beach Volumes and Widths
The data for each survey were analyzed to quantify changes in beach volume and shoreline position defined as the distance from the monument to the NGVD water line. These changes were compared throughout the entire survey period. The changes were averaged for each county and for each "developed" and "natural" segments within each county area, as will be apparent from the figure title of each graph. Finally, the average changes that occurred between each survey were




combined to obtain a cumulative response throughout theentire survey period. For illustrative purposes, the graph for the average change in volume for all Escambia County profiles will be discussed in the following paragraphs, see Figure 3.
Analysis of the data concentrated on the changes that occurred between each successive survey. However, the numbers of monuments surveyed for each time period were sometimes different from one monitoring survey to the next. Some monuments were lost due to construction or damaged due to other causes, and only half of the monuments had been established prior to the COE October 1996 surveys. In the graphs, the numbers in parentheses beside each date signify the number of monuments that the previous survey and the survey in question have in common. In Figure 3, there were twenty common surveyed profiles between the October 1996 survey and the March 1997 survey. However, three monuments were not located during the July 1997 survey, so there are only seventeen common profiles between the March 1997 and the July 1997 surveys. The number of common profiles can also be considered as an approximate measure of the confidence level, as an increase in the number of common data points yields a higher confidence in the results.
For each monument, the changes were calculated by subtracting the values (shoreline positions or volumes) of the previous survey from those of the present survey. Missing data sets occur when a particular location was not surveyed on one trip, but was surveyed on a later trip. The following example will illustrate this method: a monument is surveyed in May 1996 and October 1996, not surveyed in March 1997, but is surveyed again in July 1997 and February 1998. The difference between the October 1996 and the May 1996 surveys is calculated. Because there is no March 1997 data available for comparisons, both the October 1996-March 1997 comparison and the March 1997-July 1997 comparison are missing data sets for this particular monument. The difference in the February 1998 and the July 1997 surveys is determined and recorded. For this particular example, there are two missing data sets and two data entries. A different method of comparing the data is required when the data set is not complete; this technique is described and discussed in detail in Appendix A.
All of the differences for a particular time interval are averaged based on the total number of data sets available. The number of data sets used is noted in the graphs, as previously discussed. For each graph in which the data represents an average of several values, the standard deviation of the values entering into the average is shown as vertical bars, see Figure 3. The results for developed or natural segments are obtained by averaging the appropriately designated monuments (Table 1) according to the total number of data sets available for each respective classification.
Additional surveys and/or aerial photographs available through the DEP were used in some instances to supplement the COE data set. The following DEP surveys and aerial photography were used: for Escambia and Santa Rosa Counties, February 1996 (survey data), March 1984 (aerial photography) and October 1995 (aerial photography); for Walton County, May 1995 (survey data), March 1996 (survey data) and October 1995 (aerial photography); and for Bay County, March 1995 (survey data), February 1996 (survey data), October 1996 (survey data) and October 1995 (aerial photography). In the graphs, the asterisk next to a date indicates that the data were obtained from




Cumulative Volume Change per Unit Beach Length (yd3/ft)

I I I C0 0 -0 0 0

0 0

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C0 C0 0

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Oct 1996 (11)
- Mar 1997 (20) Jul 1997 (17)
Feb 1998 (17)

*Feb 1996 .4 May 1996 (10)




DEP surveys, instead of COE surveys. Dates in parentheses indicate that these shoreline data were obtained from aerial photography. The February 1996 survey in Figure 3 was conducted by the DEP, and the remaining five surveys were conducted by COE.
The May 1996 survey is the earliest survey conducted by COE that is common for all of the profiles. Thus, for consistency purposes, all of the changes are referenced to May 1996 for plotting purposes, and the best fit trend lines of the data begin with May 1996, see Figure 3. In addition to presenting data associated with our surveys, results are presented representing changes from preOpal conditions to immediately post-Opal and immediately post-Opal to May 1996. Specifically, shoreline position data were obtained from a time prior to the hurricanes and immediately after Hurricane Opal. The additional data sources are: Escambia and Santa Rosa Counties, aerial photographs from August 1984; Walton County, February 1995 survey data were used and; Bay County, a DEP March 1995 survey was used. The October 6, 1995 aerial photographs (two days after Hurricane Opal) were used for all counties. The pre-Opal conditions are always plotted at time zero. All other values are plotted at their actual times. For plotting purposes, May 1996 is arbitrarily selected at Year 1.0. Finally, the scale of the vertical axis for the volumetric and beach width changes are the same for all counties to allow easy visual comparison.
Between the March 1997 and the July 1997 surveys, a berm with a nominal volume of 6 yd'/ft was added to the beach in Santa Rosa County in the "developed" locations, from R-193 through R-197. This berm was constructed through an emergency program of the Federal Emergency Management Agency (FEMA). A typical profile which experienced this berm placement, R- 194.5, is shown in Figure 4. The addition of the FEMA berm is evident by reference to the preceding surveys. Because this berm nourishment would have been the primary volumetric component of change instead of natural recovery, no volumetric comparisons were made for those monuments between those two survey dates. The post-nourishment surveys, July 1997 and February 1998, were compared as usual. After the placement, the volume of sand in the vicinity of the berm placement should remain reasonably constant, even though there was some redistribution of the sand from the initial shape, see Figure 4. There is no volumetric data set listed for the developed sites for the July 1997 survey, since the beach at every developed monument was manipulated. No placement of sand occurred in the natural areas in Santa Rosa County, so the associated data are unaffected. Finally, all of the data points are used for the beach width comparisons for Santa Rosa County because the artificial nourishment was considered to have a minimal effect on the beach width.
Table 2 presents the average county shoreline positions for the pre-Erin and pre-Opal dates to immediately Post-Opal and for the period from immediately post-Opal to the May 1996 COE postOpal survey. It is seen that on average, the shoreline retreat from pre-Erin and pre-Opal to immediately post-Opal is 63.2 feet and the average shoreline advancement from immediately postOpal to the COE May 1996 survey is 58.0 feet resulting in a net retreat of 5.2 feet. Thus at the time of the first COE post-Opal survey, most of the shoreline recovery from the erosion due to the hurricanes had occur-red. This small net retreat is substantially less that the approximate 20 to 30 feet of average seasonal shoreline change along the Panhandle beaches. It will be seen that the shoreline changes over the period of COE monitoring were substantially less than from October 1995 (PostOpal) to May 1996.




20 February 1998
Artificial Berm 15
Equilibrating Berm
IF Equilibrating Berm
0
z 10
---------------- ----0
CU
5
ED
0 Gulf of Mexico
-5
0 100 200 300 400 500
Distance Seaward of Monument (ft) Figure 4. Beach Profile R-194.5 in Developed Area of Santa Rosa County.
Showing Artificially Placed Berm.




Table 2
Average Shoreline Changes: Pre-Opal to Immediately Post-Opal
and Post-Opal to First COB Survey in May 1996

County Segment Date of Photography (P) Average Shoreline Date of Photography (P) Average Type or Survey (S) Change (fi) or Survey (S) Shoreline
_________________ (Pre-Opal to Post-Opal) _________ (Post-Opal to May 1996) Change (ft)
Average -63.2 +58.0
Average of DvlpdComposite -00Composite+5.
All Four Deeoe-6.+53
Counties Natural 1__________ -67.6 _____________ +63.3
Average March 1984 (P) -46.9 October 6, 1995 (P) +78.4
Escambia Dvlpdto -35to+7.
Devloed October 6, 1995 (P) May 1996 (5)+7.
_______ Natural __ _ _ _ _ _-50.9 __ _ __ _ __ _ +81.2
Average March 1984 (P) -81.2 October 6, 1995 (P) +72.9
Santa Rosa Dvlpdto 805to+6.
Devloed October 6, 1995 (P) 805May 1996 (5)+68
Natural -81.7 +75.5
Average May 1995 (5) -64.7 October 6, 1995 (P) +23.0
Walton Dvlpdto -32to 2.
Devloed October 6, 1995(P) -32May 1996 (5)+2.
Natural -67.1 +27.0
Average March 1995 (5) Insufficient Data October 6, 1995 (P) Insufficient Data
ay Developed Oto 6,195()53.3 Mat99o5 +44.2
________ Natural October__6,__1995_(P) Insufficient Data_ May___ 1996____(S) Insufficient Datae




3.3 Dune Recovery

Individual beach and dune profiles were examined to determine the extent of dune recovery over the 1.75 year monitoring period. Although dunes on a few profiles showed a limited degree of recovery, the numbers of such profiles and the amount of recovery were not considered sufficient to conduct a detailed analysis of dune recovery. It is concluded that general dune recovery in the study area occurs on a significantly longer time scale than that of the monitoring period.
4. DISCUSSION
The averages of all of the data were plotted for each location to provide a general overview of the results. The averages for each time were plotted as well as error bars representing one standard deviation of the spread of the averaged data. For the data points that have a lower number of surveys included in the data analysis, the error bars presented are somewhat artificially reduced. A linear "best fit" straight line was plotted for the data sets so that the slope of the line represents the prevailing trend from May 1996 to February 1998, thereby encompassing the period of the COB surveys. Because of the large number of figures in this report, all of the county plots are presented in Appendix B. The composite results for the four counties are included in the main body of this report as well as in Appendix B. The summary trend values for volumetric and shoreline changes are presented in Table 3.
As Table 3 and Figure 5 show, the average overall rate of volume loss for all four counties including the February 1998 data is 2.5 yd3/fllyr. The difference between the trends in the developed areas (-2.4 yd3/ft/yr, Figure 6) and the natural areas (-2.6 yd/ft/yr, Figure 7) is not considered significant. The overall rate of beach retreat for all of the counties is 10.6 ftlyr (Figure 8) with the developed areas retreating at a rate of 9.8 fllyr (Figure 9) and the natural areas retreating at 11.4 ft/yr (Figure 10). If the effects of the erosive February 1998 storms are not included in the analysis, the rates of erosion are reduced substantially or change to accretion in both the volumetric and shoreline trends.
In Escambia County, the beach width and volume changes in the developed and undeveloped areas are approximately the same, see Table 3 and Figures B-7 through B3-12. Although natural areas are slightly more erosive volumetrically and show greater shoreline recession than the developed areas, the differences are not considered significant. The removal of the effects of the February 1998 storms from the analysis results in less erosion in all categories.
Santa Rosa County has an overall negative trend for both volume and beach changes, see Table 3 and Figures B- 13 through B3-18. Although the exclusion of the February 1998 data reduces the erosional trends, all trend values remain negative.
Overall, Walton County has the lowest erosion/greatest accretion rate of any county studied, Table 3 and Figures B3-19 through B-24. All of the rates are positive with removal of the February 1998 data.




Table 3

Beach Volume and Width Trends as Determined by the Least Squares Method County Volume Trend (yd3/ft/yr) Shoreline Trend (ft/yr)
and
Shoreline Segment February 1998 included February 1998 included
Type
Yes No Yes No
All Counties- Average -2.5 0.1 -10.6 2.7
Developed -2.4 0.1 -9.8 -0.9
Natural -2.6 0.2 -11.4 5.8
Escambia- Average -2.5 -0.2 -16.7 -12.0
Developed -2.5 0.0 -15.8 -8.2
Natural -2.6 -0.3 -17.6 -13.1
Santa Rosa- Average -2.3 -0.6 -11.6 -4.9
Developed -1.7 -4.2 -6.7 -6.7
Natural -5.2 -0.7 -15.7 -4.2
Walton- Average -1.4 3.7 4.8 34.7
Developed -1.7 4.3 1.1 30.7
Natural -1.1 3.1 8.6 36.5
Bay- Average -4.0 -3.0 -17.8 -9.7
Developed -4.2 -3.7 -16.8 -12.7
Natural -3.4 -1.4 -20.6 3.1
(Note: there are varying amounts of natural and developed areas in each of the four counties. Thus, a straight averaging method for these two shoreline types cannot be used).




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o -30
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E Time (years)
O

Figure 5. Cumulative Change in Average Volume for All Counties.




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00
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a-)
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O Time (years)

Line

2 3

Figure 6. Cumulative Change in Average Volume for All Developed Profiles.




co
a) Icu a)
-c2
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10
"-) ....... ......
0'- 0 . . . . .
0 10
.,.
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o Time (years)
Figure 7. Cumulative Change in Average Volume for All Natural Profiles




o 80)- -9 >
.0 0 0) 1C. LO (0
0 3 00
() 0-" 1,-- 0
03) 00
100 a) (020
S 80 0
Co
o 20
c
0 ....... ....
Best Fit Trend Lin
-20/Best Fit Trend Lino

o -40
a)
-60
E
S-80
o
-100
-1 0 1 2
Time (years)
Figure 8. Cumulative Change in Average Shoreline Position for All Counties.
Pre-Opal and October 1995 Positions Based on Aerial Photography.

3




o- Q
60 8 "
o O "oN
U)'
40
100 C 0-.
o -20
est Fit Trend Line
60 60
CI
40
020
CU_ -40est Fit Trend Line
-60
0
-80
-100 '
-1 0 1 2
Time (years)
Figure 9. Cumulative Change in Average Shoreline Position for All Developed Profiles.
Pre-Opal and Oct 1995 Positions Based on Aerial Photographs.

3




0
(
0 0
IL a)
0

U)
00

0
)
Ej

100
80 60
40
20
0
-20
-40
-60
-80
-100
-1.0

Best Fit Trend Line

1.0
Time (years)

2.0

3.0

Figure 10. Cumulative Change in Average Shoreline Position for All Natural Profiles.
Pre-Opal and Oct 1995 Positions Based on Aerial Photographs.

0.0




Bay County is generally characterized by negative volumetric and shoreline trends, Table 3 and Figures B-25 through B-30. This site is downdraft (west) of the entrance to St. Andrews Bay which may play a role in these predominantly erosive trends.
Overall, although quantitative differences in volumetric and shoreline trends exist between the developed and natural areas, they are not considered significant in light of the natural variability of the beach and dune system.
5. EFFECT OF FEBRUARY 1998 SURVEY
The discussions of the trends in volumetric and shoreline changes have emphasized the role of the erosive conditions documented in the February 1998 survey. In order to quantify the effect of this storm on the overall results, the data for all of the counties were reanalyzed excluding the February 1998 survey data set. The results are presented in Table 3, where it is seen that the February 1998 data represent a significant component to the overall erosive trends documented in this study.
Referring to Table 3 and Figures 5-10 for the four county composite results, it is reasonably clear that the storms which occurred between the July 1997 and February 1998 surveys caused a beach response that is as great or greater than the recovery effects of the beach system during the preceding COE period of monitoring. Figures B-7 through B-30 will document that these discussions and results are generally applicable individually to each of the four counties studied.




6. CONCLUSIONS

Changes in beach volumes and shoreline positions consist of trends due to longer term "forces" and superimposed "noise" which can vary substantially seasonally and due to individual storms and the causes of which are poorly understood quantitatively. In the present case, Hurricanes Erin and Opal caused substantial shoreline and dune erosion along the Panhandle area of Florida. The time scales of the beach and dune equilibration processes are of interest as are the degrees of recovery in areas designated as "developed" and "natural". The surveys associated with this study commenced in May 1996, some seven months after the passage of Hurricane Opal. Data obtained from pre-Opal surveys and pre- and post-Opal aerial photographs have established that the shoreline recovery was fairly rapid. The dune recovery occurs on a much longer time scale which depends on the strength of the wind, the size of the sediment and the width of the berm.
The conclusions detennined from this study are:
(1) The beach width recovers on reasonably short time scales, on the order of several months,
(2) The dune recovers on time scales on the order of years to decades, depending on several factors,
(3) The beach recession due to Hurricanes Erin and Opal was on the order of 60 to 70 feet,
(4) No clear evidence of differences between beach or dune recovery in "developed" and "natural" areas could be identified,
(5) Any dune recovery over the 1.75 years on monitoring associated with this study was small, a result of the relatively long time associated with dune recovery for the conditions (coarse sand and narrow berms) in the study area, and
(6) The natural beach and dune system is characterized by substantial natural fluctuations, for which the full causal relationships are not known, thereby complicating the interpretation of measured changes. Two individual storms before the last COE survey (February 1998) affected the overall trend rates of beach and dune change substantially.
7. REFERENCES
Federal Emergency Management Agency, 1996. Hurricane Opal in Florida: a Building Performance Assessment, FEMA 28 1. August 1996.
Leadon, Mark E., 1996. "Hurricane Opal: Damage to Florida's Beaches, Dunes and Coastal Structures", Proceedings, Ninth National Conference on Beach preservation Technology: The Furure of Beach Nourishment, Edited by D. Tait, pp. 313-328.




APPENDIX A
DESCRIPTION OF METHODOLOGY USED FOR COMPUTATIONS OF AVERAGES




APPENDIX A

DESCRIPTION OF METHODOLOGY USED FOR COMPUTATIONS OF AVERAGES One of the difficulties encountered in calculating average shoreline positions and volume changes for a number of monuments was related to the incomplete data for every time at a particular monument location. Resolution of that problem under the constraint that all available data are to be used is described below.
Table A- I is a hypothetical example of a spreadsheet denoting the original shoreline positions of various monument locations for several surveys. Monuments R-1, R-3 and R-6 are the only monuments with complete data sets. Monuments R-2, R-4 and R-5 all contain partially missing data sets. This appendix provides a detailed description of the processes used to analyze "empty" data sets.
Table A-1
Original Shoreline Positions
Time R-1 R-2 R-3 R-4 R-5 R-6
(years)
0 100 150 225 125 175 200
0.25 75 175 150 150
0.5 50 200 175
0.75 100 225 100 200 15
1 150 100 250 1'75 225 200
Table A-2 lists the changes that occurred in the original shoreline positions between surveys. Only the changes between two consecutive data sets can be obtained for reasons listed in the main body of text.
Table A-3 lists the data from Table A-2 (the changes in shoreline position) in addition to the average shoreline change for each time interval.
Table A-4 lists the shoreline changes from Table A-3, and the missing data are filled with the average shoreline change values.




Table A-2
Shoreline Changes from Original Positions

Change Between Time R-1 R-2 R-3 R-4 R-5 R-6
(years)______ _____ ______ _____ ______ __ __0.25-0.00 -25 -50 25 -50
0.5-0.25 -25 25 25
0.75-0.5 50 25 -25
IL1-0.75 1 50 _____ 25 1 75 1 25 50-j
Table A-3
Shoreline Changes from Original Positions, with Average Shoreline Change
Change Between Time R-1 R-2 R-3 R-4 R-5 R-6 Average Shoreline
(years) Change
0.25-0.00 -25 -50 25 -50 -25
0.5-0.25 -25 25 25 8.3
0.75-0.5 50 j j25 j j -25 16.7
1-0.75 50 25 175 125 150 45
Table A-4
Complete Data Set for Shoreline Changes with Average Shoreline Change Filled in all Empty Data Sets
Change Between Time R-1 R-2 R-3 R-4 R-5 R-6 Average Shoreline
(years) Change
0.25-0.00 -25 -25 -50 25 -25 -50 -25
0.5-0.25 -25 8.3 25 8.3 8.3 25 8.3
0.75-0.5 50 16.7 25 16.7 16.7 -25 16.7
I. 1-0.75 50 145 25 75 _25. 50 45




Table A-5 lists the original shoreline positions for each of the monuments, with the missing data filled in. Working backward using the changes listed in Table 4A, the shoreline positions can be reasonably estimated.
For consistency, three rules are followed-when working backward. The first rule is if there is only one missing data set from the original shoreline position spreadsheet, the value of the missing number is obtained by adding the shoreline change to the number listed above the missing value. For example, for Monument R-4, the shoreline position for time 0.5 is missing. From Table A-4, the average change between time 0.5 and 0.25 is 8.3, and the number listed above the missing data is 150 for time 0.25. Therefore, 8.3 is added to 150, and the value for the previously missing data, at time 0.5, is 158.3.
For instances where there are two consecutively missing data sets from the original
shoreline position spreadsheet, the missing data are filled in using the adjacent cell values. For example, for Monument R-5, the shoreline position for times 0.25 and 0.5 are missing. The average change between time 0.25 and 0 from Table A-4 is -25, and the number listed adjacent to the cell, the above value, is 175. Therefore, -25 is added to 175, and the value for the first missing data, at time 0.25, is 150.
The second missing data value for Monument R-5 is located at time 0.5. The adjacent cell with an original value is 200 for time 0.75. The average change between time 0.75 and 0.5, from Table A-4, is 16.7. Therefore, the average change is added to the value of the adjacent cell, and the missing data is filled with the value of 216.7.
In cases where there are three consecutively missing data sets in the original shoreline position, a combination of the first two rules are used. The top and bottom missing data value are filled in from adjacent cells, via rule two, and the middle missing data value is filled in from the number listed above. See Monument R-2 for an example of this type.
Table A-5
Complete Data Set for Original Shoreline Positions
Time R-1 R-2 R-3 R-4 R-5 R-6
0 100 150 225 125 175 200
0.25 75 125 175 150 150 150
0.5 50 133.3 200 158.3 216.7 175
0.75 100 145 225 100 200 150
1 150 100 250 175 225 200




Table A-6 contains the final shoreline position change data that would be plotted in a graph. The mean of the data and the standard deviation that are plotted are all obtained from a spreadsheet of this type.
Table A-6
Shoreline Position Changes
Change Between Time R-1 R-2 R-3 R-4 R-5 R-6
0.25-0.00 -25 -25 -50 25 -25 -50
0.5-0.25 -25 8.3 25 8.3 66.7 25
0.75-0.5 50 11.7 25 -58.3 -16.7 -25
1-0.75 50 -45 25 75 25 5L_

A-4




APPENDIX B
PLOTS OF SHORELINE AND VOLUME CHANGES




APPENDIX B

PLOTS OF SHORELINE AND VOLUME CHANGES
The thirty plots on the following pages are presented in five groups of six plots for each group. The first group represents the composite changes for all four counties and the next four groups are for the four individual counties in the following order: Escambia, Santa Rosa, Walton and Bay. The six plots within each group are, in the following order: volume changes for all profiles in the group, volume changes for "developed" profiles in the group, volume changes for "natural" profiles in the group, shoreline changes for all profiles in the group, shoreline changes for "developed" profiles in the group, and shoreline changes for "natural" profiles in the group.




30
20 2
10 **
0
-10 1*
Best Fit Trend Line
-20
-30
40 I I
-1 0 1 2 3
Time (years)
Figure B-I. Cumulative Change in Average Volume for All Counties.




400
mW
. E 1 0
0 0
co -10
o Best Fit Trend
0)
E -20o
"3
30
m
...
cu)
75 -40
0 1
OJ Time (years)

Line "

2 3

Figure B-2. Cumulative Change in Average Volume for All Developed Profiles.




")

a)

cD
._J

E C.,
=.
a)
E
U
-5
E
0

Time (years)

Figure B-3. Cumulative Change in Average Volume for All Natural Profiles

40 30
20 10
0
-10
-20
-30
-40

(0 000)0
Best Fit Trend Line
SI I




0
(U)
0 (U)
:
0
C' CU
0) .t
E


('
E) 0m

100
80 60
40 20
0
-20
-40
-60
-80
-100

Figure B-4.

0 0 )
0) a) Qa)) LL
U CU
0 I 0 0 (

Best Fit Trend Line

0 1 2 3
Time (years)
Cumulative Change in Average Shoreline Position for All Counties. Pre-Opal and October 1995 Positions Based on Aerial Photography.




CL 1- (0 N
100 ( a 0
0) CCU
80
, 60 V "D
af o 0
60 8
40
._ 20
(D
w 0
-C
o -20
S-4- est Fit Trend Line
CU-40
S-60
o
-80
-100 '
-1 0 1 2 3
Time (years)
Figure B-5. Cumulative Change in Average Shoreline Position for All Developed Profiles.
Pre-Opal and Oct 1995 Positions Based on Aerial Photographs.




100
80 60
40 20
0
-20
-40
-60
-80
-100
-1.0

0.0

Best Fit Trend Line

1.0
Time (years)

Figure B-6. Cumulative Change in Average Shoreline Position for All Natural Profiles.
Pre-Opal and Oct 1995 Positions Based on Aerial Photographs.

2.0

3.0




8-Cumulative Volume Change per Unit Beach Length (yd3
Cumulative Volume Change per Unit Beach Length (yd3/ft)

-~ N) C,3 -~ 0 0 0 0 0

4*Feb 1996 .- May 1996 (10)

Oct 1996 (11)
- Mar 1997 (20) Jul 1997 (17)

0 CD CD C,,

OO
I~ KI
C3 C)

-0 Feb 1998 (17)




30 ..
20 o
10
0 '... ... .... .
cu~
.
" -20 Best Fit Trend Line
E
2-30
S-40
S -1 0 1 2 3
E Time (years)
O
Figure B-8. Cumulative Change in Average Volume for Developed Profiles in Escambia County.




40- -*
40 ca 75
coo
- 0 0 0
E 0) 0- 0) 0 0
a 20
C0
2o
D -10
-~ 1 00 )
C, (1
E-20 Best Fit Trend Line
20 20
-30
E -40
-1 0 1 2 3
0 Time (years)
Figure B-9. Cumulative Change in Average Volume for Natural Profiles in Escambia County




0Cl
cx0 0ON
100 o
a) 0) 0) ca 03) 0)
= 80 cc
00- -.o VI ;- (3 00
:- L-L ) C
o 6 0 a u 0 o
6 0 U ?
40
- o
0 20
.c 0CD
00
S-20
o -40 -Q)
-60Best Fit Trend Line U -60
S-80
o
-100
-1 0 1 2 3
Time (years)
Figure B-10. Cumulative Change in Average Shoreline Position for All Escambia County Profiles.
March '84 and Oct '95 Positions Based on Aerial Photographs.




~-100 'o o CD 0)
10) M 0)'- (0CDD
- T O 0) M 0 co
o 0)
Z 80
-20c
o LL >, J
a-60 a )
a) L La LL
a -0 -0
10
- 20 0 0 2
) 0
-M -60
0 -80
Escambia County. Mar '84 and Oct '95 Positions Based on Aerial Photographs.




10 o0)
CY) (100 0) M
0 0 I,-80 (0 D -a0)
4) L ou
o 60
= 40
-20
-c
o -40
M-60
6 \ Best Fit Trend Line
S-80
o
-100 '
-1 0 1 2 3
Time (years) Figure B-12. Cumulative Change in Average Shoreline Position For Natural Profiles.
Escambia County. Mar '84 and Oct '95 Positions Based on Aerial Photographs.




Cumulative Volume Change per Unit Beach Length (yd3/ft)

I I I
CO3 Is)
1 1 1

- 0 0 C 0 4D
0 0 0 0 0

-n
0
I
C
m
0 0.
0" C)2
_--.
CD
-I

Oct 1996 (11)

0
O C1)
2
(D (D CI)
N)

4C- Feb 1998 (14)

0

*Feb 1996 May 1996 (9)

--Mar 1997 (20)
-4- Jul 1997 (9)




0(0
0)
0)' LL)Ca

0) LO
vO Ift(0 0) 0
0 0 0
0

cf)

0)
cu
(1)
M
-L
0)
-'
I
E
0

0 1 2 3
Time (years)

Figure B-14. Cumulative Change in Average Volume for Developed Profiles
in Santa Rosa County.

40 30
20 10
0
-10
-20
-30
-40

Best Fit Trend Linez"1




-01- co
0( -2M
00 0 ) 0
- u_ 0 0 0))
cm 1- L
r- LL 0
a)
-j 0
20
-30
co
a)
_10
-40
0
Figure B-15. Cumulative Change in Average Volume for Natural Profiles in Santa Rosa County.
E
~-40
ca
=3 -1 0 1 2 3
E Time (years)
Figure B-15. Cumulative Change in Average Volume for Natural Profiles in Santa Rosa County.




00 80-O
8 60 o : o-
O8 40
120
- 2 00
L0()
8 -0
0 u
CA 0) C 0 0
S-0
Ca)
S 40 L
0 -20
U)
-1 0 1 2 3
Time (years)
Figure B-16. Cumulative Change in Average Shoreline Position for All Santa Rosa County Profiles.
March '84 and Oct '95 Positions Based on AerialiPhotographs.
a)
c-20
cu
o -40a)
-5 Best Fit Trend Line
E -8
0 8
-100,
-1 0 1 2 3
Time (years)
Figure B-I 6. Cumulative Change in Average Shoreline Position for All Santa Rosa County Profiles.
March '84 and Oct '95 Positions Based on Aerial, Photographs.




100 -LO 0)
80 o0
60 2 M M c
8 40
oa 0 M Eo
._I
8 20
0- -20
-80
0 20
_ -40 1)

o
-100
a)
_-60 Best Fit Trend Line
E
S-80 -100
-1 0 1 2 3
Time (years)
Figure B-17. Cumulative Change in Average Shoreline Position for Developed Profiles
in Santa Rosa County. Mar '84 and Oct '95 Positions Based on Aerial Photographs.




-20 CD M 0
N--40
O CD mD 0M M 0
100 u -1 0) 0) 0M M M
80 ,
60 0 0 2L
0 60 a
a) 0
_ 40
0 20o
,)oI, 2 -__ _ __ _
U)
SataRoaCont. aB'4 endOt 9Fitins BaedoAeilPtgrps
-20
r- -2
-u -80
-8
-100 '
-1 0 1 2 3
Time (years)
Figure B-18. Cumulative Change in Average Shoreline Position for Natural Profiles in Santa Rosa County. Mar '84 and Oct '95 Positions Based on Aerial Photographs.




OZ-El
Cumulative Volume Change per Unit Beach Length (yd3/ft)
I I I I
I

C
w Co
0
C)
0
D
(D
Co
")
0 C'
0I

-o1 *May 1995
*Mar 1996 (3)
SMay 1996 (9)
Oct 1996 (9)
4 Mar 1997 (20)
-P4--- Jul 1997 (20)

-. Feb 1998 (16)

"n




Cumulative Volume Change per Unit Beach Length (yd3/ft)

I I I
111
0 00

".1
-n
CD
0
(D
14
su
0 5.
CD
=,.
CD
-I
0
0
0 0I

0 0 C) C

0 -0 0) 0

*May 1995

*Mar 1996 (2)
- May 1996 (5)
Oct 1996 (5)
4 Mar1997 (10) -- Jul 1997 (10)
- Feb 1998 (8)

1
40
I

CD CD Cl)

CD CD




z-Cumulative Volume Change per Unit Beach Length (yd3
Cumulative Volume Change per Unit Beach Length (yd3/ft)

"1
-n
e
w
CC
_3
.o o
CD
<
E, o ".
0
0 O 0o
0I

I I I I
0 0 0 0 0 0 00o0o o o
o 0

*May 1995
--S *Mar 1996 (1) 4t- May 1996 (4)
SOct 1996 (4)
-*- ~Mar 1997 (10)
-A$- Jul 1997 (10)

-Feb 1998 (8)




100-0
LO .0
0 ) %- -- N 0
0) 0) 0' ) ) 0
S 0(0 M
60
P -20
S-40 )Best Fit Trend Line
-60
-80
100 ''
-1 0 1 2 3
Time (years)
Figure B-22. Cumulative Change in Average Shoreline Position for AII Walton County
Profiles. Oct 1995 Positions Based on Aerial Photographs.
60
0~
C
o -20 etFit Trend Line
CU -60
E -80-100 F
-1 0 1 2 3
Time (years)
Figure B-22. Cumulative Change in Average Shoreline Position for All Walton County
Profiles. Oct 1995 Positions Based on Aerial Photographs.




(D
gVO 0)
0) LO () .
cu 0)
0

100
80 60
40 20
0
-20
-40
-60
-80
-100

0 1 2 3
Time (years)

Figure B-23. Cumulative Change
in Walton County.

in Average Shoreline Position for Developed Profiles Oct '95 Positions Based on Aerial Photographs.

Best Fit Trend Line




800 OO
0C4
0) ) !'0 N
200 "-...... ---"C- 000)
Le 0
o -4 0 0
)0)
-6 0 70
-100
cui
0 80 a)IiL
-1) 0 0
60
_: 40
0 20 .....
--. . . .
U 0/ /
0)
Tim (yars
F-20i
cu
o -40
> Best Fit Trend Line
-u -60
E
2 -80
-100 1 ,
-1 0 1 2 3
Time (years)
Figure B-24. Cumulative Change in Average Shoreline Position for Natural Profiles
in Walton County. Oct '95 Positions Based on Aerial Photographs.




9Z-e i
Cumulative Volume Change per Unit Beach Length (yd3/ft)

I I I
C C) ) C)
111

-I
,
0
<
O
o
,
o
0
=h
S

- 0 ) 0 0
0 0 o 0 0

May 1996
- *Oct 1996 (6)
--- Mar 1997 (18)
-_ Jul 1997 (15)

Feb 1998 (15)

C)
I

0
--!
3
(D) CD CD
1-)

Oct 1996 (10)




4 30 S 400
.e20 O l
0-30
cc
a)
> 10
CL
-40
- -1 0 1 2
a)
-10 0
20 Best Fit Trend Line(years)
E ~-30
=3 -1 0 1 2
E Time (years)
0

Figure B-26. Cumulative Change in Average Volume for Developed Profiles in Bay County.

3




203
1- 101
00
30 ca
S 20
.- Best Fit Trend Lin
ciz
S-30
Do
000
-40
> 30BetFtTedLn
a) I I I 0
-5 -1 0 1 2 3
E Time (years)
0
Figure B-27. Cumulative Change in Average Volume for Natural Profiles in Bay County.
Figure B-27. Cumulative Change in Average Volume for Natural Profiles in Bay County.

e




LO L0
Mco-
o0600o CD CD
S100 ( (~ 0) ) N-cc
CU ) a) a)- a,
80 4 a
00
* -20 "
o -40
- 60
- -80Best Fit Trend Line
0
L..I
0 20
coo
-100
O-40
a)
S-60
75 -8 Best Fit Trend Line0
o 800
-1 00 I
-1 0 1 2
Time (years)
Figure B-28. Cumulative Change in Average Shoreline Position for All Bay County
Profiles. Oct 1995 Positions Based on Aerial Photography.

3




l I (.0 0O()
0) 0' a) V

(0 %
0) N-

100 0) -.
100 OM Uv ~~LL U' '- I '
- u 0
'o 80 _o 0 co0).
o -40
- -TO
= -80Best Fit Trend Line
E In-- I
-O
M
- 10
a)
-1 0 1 2 320
Time (years)
Figure B-29. Cumulative Change in Average Shoreline Position for Developed Shorelines
-in Bay County. Oct 1995 Positions Based on Aerial Photography. o -0
a)
~ -80
in Bay eouty Ot 1995d Poionsae nAralPoorpy




oo600-)
0)0 cx
40
860 a) 0
I,.- T
oC
) 207
0 -0
0
a2)
-40
00 E -60-1 0 1 2
Time (years)
Figure B-30. Cumulative Change in Average Shoreline Position for Natural Profiles in Bay County.

o
0 I)
w

nd Line

3

(D3