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 Front Cover
 Title Page
 Scope of the report
 Experimental conditions
 Comparisons of experimental...
 Summary
 References






Group Title: UFL/COEL (University of Florida. Coastal and Oceanographic Engineering Laboratory); 94/005
Title: Evaluation study and comparison of erosion models and effects of seawalls for coastal construction control line
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00084999/00001
 Material Information
Title: Evaluation study and comparison of erosion models and effects of seawalls for coastal construction control line interim report #3
Series Title: UFLCOEL-94005
Alternate Title: Physical modelling progress report for evaluation study and comparison of erosion models and effects of seawalls for coastal construction control line
Physical Description: 48 leaves : ill. ; 28 cm.
Language: English
Creator: Charles, Lynda L., 1962-
Lin, Li-Hwa
Dean, Robert G ( Robert George ), 1930-
University of Florida -- Coastal and Oceanographic Engineering Dept
Florida -- Dept. of Environmental Protection
Publisher: Coastal & Oceanographic Engineering Dept., University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1994
 Subjects
Subject: Storm surges -- Mathematical models   ( lcsh )
Coastal engineering -- Mathematical models   ( lcsh )
Sea-walls -- Models   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaf 48).
Statement of Responsibility: by Lynda L. Charles, Lihwa Lin, and R.G. Dean ; prepared for Department of Environmental Protection, State of Florida.
General Note: At head of title: Physical modelling progress report for.
General Note: "April 25, 1994."
Funding: This publication is being made available as part of the report series written by the faculty, staff, and students of the Coastal and Oceanographic Program of the Department of Civil and Coastal Engineering.
 Record Information
Bibliographic ID: UF00084999
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 30993353

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Scope of the report
        Page 1
        Page 2
    Experimental conditions
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
    Comparisons of experimental results
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
    Summary
        Page 47
        Page 48
        Page 46
    References
        Page 48
Full Text



UFL/COEL-94/005


Evaluation Study and Comparison of Erosion Models and
Effects of Seawalls for Coastal Construction Control Line





Interim Report # 3


by


Lynda L. Charles
Lihwa Lin
and
R.G. Dean


April 25, 1994


Prepared for:


Department of Environmental Protection
State of Florida












Physical Modelling Progress Report for:


Evaluation Study and Comparison of
Erosion Models and Effects of Seawalls for
the Coastal Construction Control Line


Interim Report #3


by
Lynda L. Charles
Lihwa Lin
and
R.G. Dean




Prepared For:
Department of Environmental Protection
State of Florida
Gainesville, Florida


April 25, 1994


I









1.0 SCOPE OF THIS REPORT


This report presents results from wave tank experiments recently performed at the University of Florida's
Coastal and Oceanographic Engineering Laboratory facilities in Gainesville, Florida. These experiments comprise

a portion of the physical modelling aspect of a DEP Coastal Construction Control Line study. The main objective

motivating the physical modelling is to evaluate seawall effects on adjacent beaches under controlled forcing

conditions.


Table 1 summarizes the experimental cases and test parameters employed in the wave tank studies

completed to date. The shaded experiments in Table 1 are discussed and compared in sections 3.1 through 3.4 of
this report. The various experimental parameters listed in Table 1 are described in more detail in Section 2.0 of

this report.


The wave tank experiments were designed to serve as sensitivity tests for individual experimental
parameters. Each comparison in this report is made between two experiments which differ in only one parameter,

thus providing insight into the effect of that single parameter. Table 2 provides a summary of the experimental

parameters varied for each comparison presented in this report as well as those evaluated in the two previous interim

reports.


In brief, the first interim report compares experiments A2 and B1. These experiments vary only in
sediment size. The second interim report, which presents the results of the four C-series experiments, expressly
investigates scour adjacent to the seawall for regular versus random waves with two different wave periods and a

time-invariant surge water level (SWL).


In the present report, four regular wave experiments each with unique time-varying storm surge conditions
are compared in Section 3.1 which covers the results of experiments Al, A2, B2, and B9. Section 3.2 of this

report focuses on the results of experiments B6, B7, B8, and B9 in order to investigate the effect of different wave

types (regular versus random) on the model beach profile in the vicinity of a seawall under time-varying storm surge

conditions. Section 3.3 examines the effect of lowering the initial model beach profile while leaving all other
experimental parameters unchanged. Section 3.4 focuses on the results of experiments B5 and B6 in which wave

energy is the only experimental parameter that differs between these two random wave experiments. Section 3.5
summarizes the findings from sections 3.1, 3.2, 3.3, and 3.4.










Table 1. Summary of experimental cases and test parameters where the shaded portions indicate those experiments

which are discussed in the present report.


water level characteristics seawall characteristics sediment wave characteristics water
stepwise time-varying const. straight, vertical median wave type deep water wave volume
Experiment storm surge level seawall top diameter regular random wind wave height [cm] period overtopping
Series model peak level [cm] [cm] model elevation [cm] [mm] waves waves waves time [s] seawall
14.4 16.8 14.4 21.12 22.34 19.90 0.18 0.09 16.0 15.0 varied 1.65 1.30 measured
#1 #2 #3 #4 #5 #1 #2 #3 #1 #2 #1 #2 #3 #1 #2 #3 #1 #2


Al X X X X X X
A2 X X X X X X
A3 X X X X X X X
A4 X X X X X X X X
B1 X X X X X X
B2 X X X X X X
B3 X X X X X X
B4 X X X X X X
B5 X X X X X X X
B6 X X X X X X X
B7 X X X X X X
B8 X X X X X X
B9 X X X X X X
C3 X X X X X X X
C4 X X X X X X X
C5 X X X X X X X
C6 X X X X X X X
S3 X X X X X X
T3 X X X X X X
R3 X X X X X X X
R4 X X X X X X X
N1 X X X X X
N2 X X X X X
F1 X X X X X X
F2 X X X X X X
F3 X X X X X X
F4 X X X X X X









Table 2. Listing of the experiments compared in the present and previous interim reports.





INTERIM VARIED EXPERIMENTAL PARAMETERS EXPERIMENTS
REPORT [model units] COMPARED



#1 sediment size: [0.18mm] vs. [0.09mm] A2 B1
#2 wave period: [1.65s] vs. [1.30s] C3 C4
C5 C6
wave type: regular vs. random C3 C5
(for time-invariant SWL) C4 C6
#3
section 3.1 storm surge: peak level [14.4cm] vs. [16.8cm] Al A2
B2 B9
section 3.2 wave type: regular vs. random B6 B7
(for time-varying SWL) B9 B8
section 3.3 initial profile elevation: unchanged vs. lower B6 B9*
B7 B8*
section 3.4 wave energy: [Ho=15cm] vs. [Ho= 16cm] B5 B7


2.0 EXPERIMENTAL CONDITIONS



2.1 Laboratory Facility


The laboratory experiments were conducted in the air-sea tank at the University of Florida Coastal and

Oceanographic Engineering Laboratory. The tank section used for the experiments is 37 meters long, 0.9 meters

wide and 1.2 meters high (Figure 1). The tank is equipped with an hydraulic powered wave maker located at one

end of the tank. This wave maker is capable of generating regular and irregular waves controlled by a Wavetek

Model 110 computer system. Also located at this end of the tank is a powered fan used to generate wind waves.

A wave energy absorbing basin is located at the far end of the wave tank where the model beach is located.






















LEV.(fl


Figure 1. Schematic diagram of wave tank facility.









Above the wave tank, there is an electrically powered trolley capable of moving over the entire length of

the wave tank. This trolley is used in measuring the model beach profiles in the following way. Along the entire
length of the model beach, a grid is marked on the top of the wave tank wall. The trolley is equipped with a
graduated vertical rod which can be raised and lowered manually. By stopping the cart at predetermined increments
along the grid, model beach elevations are then measured by lowering the graduated rod so that it just rests on the
sand and an elevation is read from the graduated survey rod. Horizontal distances are adjusted with zero datum

at the seawall location. Elevations are referenced to the DNR vertical datum of NGVD. These surveys were

conducted at various time intervals for each experiment depending on the objectives and time allotted (Table 3).


Two capacitance type wave gages were installed in the tank for monitoring waves. Gage #1 is located 18.3
meters (457.5 meters prototype) seaward of the seawall and Gage #2 is located 5.3 meters (132.5 meters prototype)
seaward of the seawall.


The volume of water overtopping the seawall is measured during some experiments by collecting the water
in a movable catch pan located immediately landward of the seawall. Measurement of this overtopping volume
requires the experiment to be run twice. The profile response behind the seawall is also of interest, thus, the

experiment must be performed once for each measurement.


2.2 Scaling


A model to prototype length scale ratio of 1:25 and time scale ratio of 1:5 are used in all studies. This
means that, for instance, a distance of 1 meter in the model corresponds to a distance of 25 meters in the prototype
or actual case being modelled. Likewise, a time duration of 1 second in the model corresponds to a time duration
of 5 seconds in the prototype. The dimensions in this report are primarily given in model units followed by
prototype units in parentheses.


2.3 Initial Profile and Seawall Configuration


The initial profile used in the 27 experiments listed in Table 1 is modelled after an actual beach profile in

Highland Beach located in Palm Beach County. This profile coincides with the DNR Range Number R-192. The
model initial profile is presented in Figure 2.










Table 3. Time intervals for the surveys of the model beach profile which were performed in each experiment.


experiment time of model beach profile surveys in hours total
series number
model: 00 0.6 1.2 1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0 6.4 6.6 7.2 7.6 7.8 8.4 9.0 of
prototype (00) (03) (06) (09) (12) (15) (18) (21) (24) (27) (30) (32) (33) (36) (38) (39) (42) (45) surveys


Al X X X X X X X X X X X X X X 14
A2 X X X X X X X X X X X X 12
A3 X X X X X X X X X X X X 12
A4 ___X X 2
B1 X X X X X X X X X X X X X 13
B2 X X X XX X X 7
B3 X X X X XX X 7
B4 X X X X X X X 7
B5 X X X X X X 6
B6 X X X X X X 6
B7 X X X X X X 6
B8 X X X X X X 6
B9 X X XXXX X 7
C3 X X X X 4
C4 X X X X 4
C5 X X X X 4
C6 X X X X 4
S3 X X X X 4
T3 X X _X XX X X 7
R3 X X X X X X X X X X 10
R4 X XXXXXXX X X X X 10
N1 X X X XX X X 7
N2 X X X X X X X 7
Fl X X X X X X X 7
F2 X X X X X X X 7
F3 X X X X X X X 7
F4 X X X X X X X 7
total:194


-6-














0.25

0.20

Z 0.15

0.10

.2 0.05

(3 0.00

E -0.05

-0.10


2.5 3.0 3.5


Figure 2. Typical model beach initial profile.








There are three simple, vertical seawalls listed in Table 1. Since these three model seawalls varied only

in seawall height, they were constructed out of the same piece of 2.54-cm thick plywood which was placed at three

different elevations to create the three seawalls modelled. The seawall location along the profile was fixed for all

the experiments listed in Table 1 which involved seawalls. The first one, Seawall #1, is modelled after the actual

seawall located at R-192 which has a model elevation of 21.12 centimeters (5.28 meters prototype). Seawall #2 is

1.22 centimeters (model) higher than Seawall #1 and Seawall #3 is 1.22 centimeters (model) lower than Seawall

#1. Thus, Seawall #2 has a model elevation of 22.34 centimeters (5.59 meters prototype) and Seawall #3 has a

model elevation of 19.90 centimeters (4.98 meters prototype).



2.4 Storm Surge



Four time-varying severe surge conditions are modelled in the various experiments listed in Table 1. They

are referred to as storm surges #1, #2, #3 and #4. These severe surge conditions are numerically determined

combined total storm tides which have been established for various portions of Palm Beach County (Dean et al.,

1992). These total storm tides include storm surges, astronomical tide, and dynamic wave set-up which occurs


-7-


-0.5 0.0 0.5 1.0 1.5 2.0
model distance from seawall [meters]


1.0


--seawall # 2
election o.223m initial profile








NGVD


---- 0 minutes elapsed -----














> 3.5 14



2 2.05I I I






-0.5 --- continuous prototype surge stepwise model surge 2-----2
-1.0 I I I -4
0 5 10 15 20 25 30 35 40 45




Figure 3. A continuous storm surge hydrograph, which is typical of the prototype, compared with a corresponding

stepped storm surge, which is typical of those modelled in the experiments.



primarily in the inner surf zone (landward of wave breaking). The storm tides are physically modelled in the wave
tank by raising the water level in a step-wise fashion. Figure 3 is a schematic of the continuous storm surge profile

of the prototype and the stepped simulation which was applied in the model experiments.


Inr contrast to the time-varying water level of the aforementioned storm surges, Storm Surge 5 is a time-

invariant water level. Storm Surge #5 is modelled by fixing the surge water level (SWL) at 0.144 meters (3.6 m

prototype). This water level is the predicted peak value for the Highland Beach area in Palm Beach County. This

constant storm surge was used in the Series-C experiments listed in Table 1.


2.5 Sediment Size


Median diameters of the two sediments listed in Table 1 are 0.18 mm for Sand #1 and 0.09 mm for Sand

#2. Based on fall velocity similarity, these model diameters correspond to prototype values of approximately 0.65

mm and 0.21 mm, respectively. The cumulative grain-size distributions are presented in the first interim report

(Thompson et al., 1993). The coarser sediment, Sand #1, is used in all of the Series-A experiments. The finer

sediment, Sand #2, is used in all the remaining experiments.









2.6 Wave Conditions


Both regular and random waves are modelled in the wave tank experiments listed in Table 1. The regular

waves are modelled with a deepwater wave height of 0.16 meters for all the experiments completed thus far. This

model wave height corresponds to a prototype value of 4.0 meters. Two different wave periods are modelled in the

regular wave experiments listed in Table 1. Wave Period #1 is 1.65 seconds in the model (8.25 seconds prototype)

and Wave Period #2 is 1.3 seconds in the model (6.5 seconds prototype).


The random waves are modelled by a Pierson-Moskowitz spectrum with a deepwater significant wave height

of 0.16 meters (4.0 m prototype). The exception is B5 which is a random wave experiment with a significant wave

height of 0.15 meters (3.75 m prototype). For the random waves, two modal wave periods are modelled. These

correspond to wave periods #1 and #2 listed in Table 1. Figure 4 shows the spectral densities for the random wave

experiments B5 and B7 discussed in Section 3.4 and Figure 5 shows the spectral densities for the random wave

experiments B7 and B8 discussed in Section 3.3. The measurements are from Gage #1 located 18.3 meters (457.5

meters prototype) seaward of the seawall.






60 1----------- -----------------------I


50- ---------- ,-- -

experiment: B5 B7
Hs [m]: 0.15 0.160
40- ----------- ---Tm [s]: 1.650 1.650




I-
I 30 .-.-.-.-.- -. . -


20 ------------ -------------

S------------B5 ----- -B7

IV
r

0.0 0.5 1.0 1.5 2.0
frequency [hertz]


Figure 4. Spectral densities for random wave experiments B5 and B7 measured 18.3m seaward of the seawall.


-9-










-I C ApClIICIIHL. DI DO
o50 --------- -- Hs [m]: 0.160 0.160
< a Tm [s]: 1.650 1.650
40 -i --i -----



o 20 ------------------ -- --- -------------- B7 B8 ----

10 -- -- -- -- -- --- -- -- -- -\ A- -: -- - - -
40 I _______ _____
0.0 0.5 1.0 1.5 2.0
frequency [hertz]

Figure 5. Spectral densities for random wave experiments B7 and B8 measured 18.3m seaward of the seawall.




3.0 COMPARISONS OF EXPERIMENTAL RESULTS

The four different time-varying storm surges used in the wave tank experiments are presented in Figures
6 through 9. Notice that in each of these figures there are four separate time intervals which are identified as Stages
1 through 4. These time intervals correspond to the major transitions in the surge water level (SWL) around the
peak period and are described as follows:
Stage 1: the pre-escalation period which includes all the minor fluctuations in the SWL prior to the peak
level.
Stage 2: the SWL escalation period which commences after the pre-escalation period and ends just prior
to the achievement of peak SWL.
Stage 3: the peak SWL period which for all experiments covers 36 minutes (3 hours prototype).
Stage 4: the descending SWL period which begins as the SWL is lowered from its peak level and
concludes just prior to the minor fluctuations in SWL which follow the peak.

The arrows in each storm-surge figure (Figures 6 through 9) point out the position of the SWL at the time
in which the model beach profile was measured. The survey data collected at the end of each of these time intervals


- 10-










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Figure 8. Storm Surge #3, arrows mark the position of the SWL at the four times for which model beach profiles

were surveyed.


Figure 9. Storm Surge #4, arrows mark the position of the SWL at the four times for which model beach profiles

were surveyed.


-12-


4.5 18
/4.0 -Stage 3 -16
> 4.0 Storm Surge #3 | -stage 3 .16
S3.5 14
I3-0 /-12
3.0 Stage2
S2.5 0
2.0 / Stage 4 -


Stage 1S

0.0 0

-0.5 prototype storm surge- stepwise model surge -2
-1.0 -r -TI -- -I ---- r -i 1 -4
0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45
prototype time [ hours ]


4.5 18

S4.0 Storm Surge #4 --Stage3 16
3.5 14

3.0 tageS2 12
2.5 10
2.0 / Stae 4 8
1.5 6
1.0 4
SStagel / '
0.5 -2
S0.0 0
8 -0.5 prototype storm surge stepwise model surge -2
-1.0 1 1 1 1.. 1-4
-3 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42
prototype time [ hours ]









have been selected for all the comparisons presented in this report so these figures will serve as a useful reference

throughout the remainder of this discussion section.


In this section, all the figures which follow contain four graphs per page which correspond to the above-
mentioned time intervals. For each comparison, there are two sets of figures. The first set of figures shows the

profile at the four selected time intervals as well as the difference in elevation of this profile from the initial profile.

This is done for each experiment individually to show the actual profile shape and the changes which occurred from
the initial profile to obtain this final shape. The second set of figures facilitates the comparisons between

experiments by plotting the difference from the initial profile for both experiments together at each of the four time

intervals. By comparing the differences from the initial profile rather than the profile itself, any inadvertent

discrepancies in the initial profile configuration between experiments are minimized.




3.1 Effects of Storm Surge Level


The effect of having different storm surge conditions on the model beach profile immediately adjacent to

a seawall is investigated in this subsection by comparing Experiment Al to A2 and by comparing Experiment B2
to B9. Storm surge is the only experimental parameter which differs between the two experiments in each

comparison. The four different storm surges used in the experiments are shown in figures 6 through 9. The peak
surge elevations differed by 2.4 em (model) between Al and A2, as well as between B2 and B9.


In addition to the differences in storm surge among the four experiments which are compared in this

section, the Series-A experiments were performed with coarser sediment (model median diameter 0.18mm) and the

Series-B experiments were performed with finer sediment (model median diameter 0.09mm). The cumulative grain-
size distributions for both sediments are presented in the first interim report (Thompson et al., 1993).


The experimental parameters for Al and A2 are listed in Table 4 where the shaded parameters are those

parameters which are the same for both experiments. Similarly, Table 5 lists the experimental parameters for B2

and B9. All four experiments were performed with regular waves with a model wave period of 1.65 seconds and

a deepwater wave height of 16 cm. The seawall is a simple, vertical wall with a model elevation of 22.34

centimeters (5.59 meters prototype).


- 13 -










Table 4. Experimental parameters for Al and A2 with common values shaded.

Experimental Al A2
Parameter model prototype model prototype


peak surge [m] 0.144 3.600 0.168 4.200
wave type regular regular regular regular
wa\e period [sl 1.650 8.250 1.650 8.250
sed. median diam. [mmI 0.180 0.650 0.180 0.650
seawall heighL [m] 0.223 5.585 0.223 5.585




Table 5. Experimental parameters for B2 and B9 with common values shaded.

Experimental B2 B9
Parameter model prototype model prototype


peak surge [m] 0.144 3.600 0.168 4.200
wave type regular regular regular regular
wave period [sl 1.650 8.250 1.650 8.250
sed. median diam. Imm] 0.090 0.210 0.090 0.210
seawall height [m] 0.223 5.585 0.223 5.585


All four model experiments (Al, A2, B2, and B9) were run for a total of at least 7.8 hours (39 hours

prototype). Profiles were measured at the end of each of the four time intervals described previously. These

profiles are the solid lines shown in Figures 10 through 13. The position of the SWL at the end of each time

interval is presented in these figures as a straight, solid line. The dotted lines in these figures are the differences

in profile elevation from the initial profile. Several general observations can be made from these figures.


The general erosive and accretive trends are similar in experiments Al, A2, B2, and B9 which are

examined in this section. The primary observable trend occurs at the point of intersection of the SWL with the

profile and in the area immediately landward of this point. For the case that the SWL intersects the sand beach,

local accretion occurs and there is no change in the profile landward of the seawall. For the situation where the

SWL intersects the seawall, which results in a totally submerged beach, local scour occurs at the seawall toe and


- 14-









erosion occurs landward of the seawall in magnitudes which increase with higher water levels and longer time

durations of these elevated water levels.


The elevation differences from the initial profile for experiments Al and A2 are plotted together in Figure
14 for each of the four time intervals. Likewise for B2 and B9 in Figure 15. In both figures, the experiment with

the higher peak SWL is plotted as the dotted line and the experiment with the lower peak SWL is the solid line.

Figures 14 and 15 summarize the profile evolution for the four time intervals aforementioned.


At the end of Stage 1, the pre-escalation phase, the SWL intersects the sand beach in all four experiments.
Accretion occurs at and immediately landward of this intersection area in all four experiments. In both

comparisons, the experiment with the higher SWL exhibits accretion closer to the seawall than the corresponding

lower SWL experiment. Notice that experiment B9, the higher SWL experiment of the finer sand experiments,

exhibits significant accretion in the area between 2.5 and 3.5 meters seaward of the seawall. None of the other

three experiments experience such significant accretion in this region of the profile.


At the end of Stage 2, the SWL escalation phase, the SWL continues to intersect the sand beach for Al
and A2 but this point of intersection is closer to the seawall than it was at the end of Stage 1. Figure 14 shows that

the material accreted during Stage 1 migrates landward with the higher SWL at the end of Stage 2.


For B2 and B9, the SWL intersects the seawall at the end of Stage 2. The material accreted at the end of

Stage 1 for both experiments is transported seawards by the end of Stage 2. Local scour at the seawall toe for B9,

the higher SWL experiment, is significantly greater than the other experiments at this same time interval. Erosion

landward of the seawall also occurs in B9.


At the end of Stage 3, the peak SWL phase, the beach is submerged in all four experiments. Scour at

the seawall toe is present at this stage in all experiments except B9 which experiences complete recovery from the
scour which occurred during the previous stage, Stage 2. Erosion landward of the seawall is severe for B9,

however. Significant erosion occurs landward of the seawall for A2 and B2, also, although not to the extent of B9.


At the end of Stage 4, the descending SWL phase, the beach is subaerially exposed in all four

experiments. More beach is exposed however in Al and A2, which are the coarser sediment experiments, than is


- 15 -












seawall # 2
elevation 0.223m


Experiment Al


U.-" .


Storm Surge #1
pre-escalation of SWL
3.0hours elapsed (model)


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Z o.m-


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a
-04.10

0.30

5Q 0.25
U
Z 0.20



V 0.10
e

S0.05

^ 0.00



-0.10,


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0
model distance from seawall [meters]


2.5 3.0 3.5 4.0


Figure 10. Model beach profiles and elevation differences from the initial profile -- experiment Al.


- 16-


SWL: 0.048m


Storm Surge #1
seawall # 2 SWL escalation
nation 0.223m 4.2 hours elapsed (model)
elevation 0.223m














.1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.(


Storm Surge #1
seawall # 2 peak SWL
-r 4.8 hours elapsed (model)



SWL: 0.144m





NGVD .. ... ... .. .... --.. ...





1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.(


Storm Surge #1
seawall # 2 descending SWL
elevation 0.223m 5.4 hours elapsed (model)
-L

















NGVD ,..w-... m-... ..............
.... -- ... .---- r .... .............ro mi i

-- model beach profile ...--....... difference from initial
evaion 0.23m5. hor odl


2.5 3.0 3.5 4.0


4.0o -0.5 0.0 0.5 1.0 1.5 2.0










0.30-

0.25

Z 0.20-

0.15 -

0.10 -

0.05 -
4)


Experiment A2


seawall # 2

elevation 0.223m


Storm Surge #3
pre-escalation of SWL
3.6 hours elapsed (model)


SWL: 0.06m


NGVD


-0.05 -

0.10
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30
Storm Surge #3
025 seawall # 2 SWL escalation

0.20 elevation 0.223m 4.2 hours elapsed (model)


0.15
O.l -SWL: 0.144m
'0.10 -




0.00- NGVD ---- -

-0.05 -

-0.10
.1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


0.30
Storm Surge #3
0.25 seawall # 2 descending SWL

Salvation 0.223m 5.4 hours elapsed (model)
0.:0 elevation 0.223m

0.15 -

0.10 SWL: 0.072m

0.05 N

n00 NGVD ....-- -....-.-.---.. .-- ... ..---...---------- .........................


-0.05 -

-0.10 -
-1.0


-0.5 0.0 0.5 1.0 1.5 2.0
model distance from seawall [meters]


2.5 3.0 3.5 4.0


Figure 11. Model beach profiles and elevation differences from the initial profile -- experiment A2.


- 17-


0




"s





z
i
0
'4
4)
4)


03


model beach profile -- d e fm

{- model beach profile .............. difference from initial


7 1


-


I








Experiment B2


U.JU

0..5 seawall # 2 Storm Surge #2
Spre-escalation of SWL
o.: elevation 0.223m 3.0hours elapsed (model)

0.15 -

0.10-

0.05 SWL: 0.036m



-0.05
NGVD




-0.10

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30-

Storm Surge #2
0.25 seawall # 2 SWL escalation

.- eevation 0.223m 3.6 hours elapsed (model)

0.15

0.10 SWL: 0.12m

0.05

0. NGVD ------------------------------

-0.05


-0.10
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

Storm Surge #2
0.2- seawall # 2 peak SWL

ovation 0.223m 4.2 hours elapsed (model)
elevation 0.223m


0.15
SWL: 0.144m
0.10

0.05 -

0.o0 NGVD
-- ------ ---- ---- -- ....
-0.05

-0.10


-1.0
0.30 --

0.25

0.20

0.15 -

0.10

0.05 -

0.00 -
-oo
-0.05

-0.10 -


Figure 12. Model beach profiles and elevation differences from the initial profile -- experiment B2.


- 18-


-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5










0.30

S0.25
0
Z 0.20
I-
S0.15

Y 0.10

0.05

) 0.00

-0.05




0.30

S0.25

Z 0.20

S0.15

0.10
0
0.05

S0.00

"s -0.05

-0.10
-.o

0.30

0.25

Z 0.20
a-
9 0.15

S0.10
o.oI
S 0.0:1s
4)


Storm Surge #4
peak SWL
4.2 hours elapsed (model)


SWL: 0.168m


NGVD


* I


"O.0 .....
0..0



. 0 .i. .. .. .
-.n 11 -r _________i*-*'_________________________________________


-1.0 -0.5 0.0


seawall # 2

elevation 0.223m


0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


seawall # 2 Storm Surge #4
descending SWL

elevation 0.223m 4.8 hours elapsed (model)




SWL: 0.072m







--- model beach profile -......... difference from initial

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
model distance from seawall [meters]


Figure 13. Model beach profiles and elevation differences from the initial profile -- experiment B9.


- 19-


Experiment B9




seawall # 2 Storm Surge #4
pre-escalation of SWL
elevation 0.223m 3.0 hours elapsed (model)





SSWL: 0.06m

.. ............ -.. 1...... .....
NGVD





-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0



seawall # 2 Storm Surge #4
SWL escalation
elevation 0.223m 3.6 hours elapsed (model)


SWL: 0.144m





NGVD .......... .. 5- ..------- ..





1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


a


-0.5 0.0


-1.0
0.30

0.25 -

S0.20 -

I-
0.15

'-' 0.10



o o.


0 -0.05 -


-0.10


h...~C







Comparison Between Al and A2


0.30 -

0.25 -

S0.20W-

0.15 -

0.10 -

S 0.05 -

. 0.00

S-0.05 -

> -.10 -
4)..


0.30

0.25
.5 peak SWL

0.20 experiment: Al A2
seawall #2 SWL [m]: 0.144 0.168
seawall # 2


0.10

0.05 -

0.00

0.05 ..

0.10 -

0.15
.1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 descending SWL
experiment: Al A2
0.20 SWL [m]: 0.096 0.072
seawall # 2
0.15 location

0.10 -

0.05 -

0.00 N

0.05 -

0.10 experiment Al -......... experiment A2

0.15 -


-1.0


-0.5 0.0 0.5


1.0 1.5 2.0
model distance from seawall [meters]


2.5 3.0 3.5 4.0


Figure 14. Elevation differences from the initial profile -- comparison between Al and A2.


-20-


pre-escalation of SWL
experiment: Al A2
SWL [m]: 0.048 0.060


seawall # 2
location


.1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


-a
'*1


0



I
'4
d



0-









o
4)
1-




CO


tI
4)



^1
C.)




4)
Ia





4)-


i I


-----.l.~ r~.............- ~







Comparison Between B2 and B9


0.30

0.25





0.10
a 0.05



-0.05

S-0.10
) 0.05
4a


i .i
lU -...


pre-escalation of SWL
experiment: B2 B9
seawall # 2 SWL [m]: 0.036 0.060
location


. .


i I ------ ___
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.(
0.30

0.25 -
SWL escalation
0.20 experiment B2 B9
SWL [m]: 0.120 0.144
o.15 seawall # 2
/0.10 / location
0.10 -

0.05-

-.. --------- 14------------- -------------................. ...
-0.05 -

-0.10

-0.15 ,,,,


0.30

J 0.25
peak SWL
0.20 experiment: B2 B9
.15seawallSWL [m]: 0.144 0.168
Seawall #2
0 location
I-
I 0.10 -

S0.05 -



S-0.05 "".

1)
> -0.10 -

-0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

S0.25- descending SWL
experiment: B2 B9
a 0.20 SWL [m]: 0.048 0.072
seawall # 2
01 / location

0.10






-1.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


model distance from seawall meters
S-0.10 experiment B2 ............ experiment B9 I


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
model distance from seawall [meters]


Figure 15. Elevation differences from the initial profile -- comparison between B2 and B9.


-21 -


0
4)
C)
O

a



I-
'Y3

I
4-o




p,
0


-1


------~~-~~,~'


-1.n -.i


0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0









exposed in B2 and B9, which are the finer sediment experiments, and there is a corresponding difference in profile

response. The coarser sediment experiments exhibit significant accretion immediately seaward of the seawall,

whereas, the finer sediment experiments remain relatively unchanged in this same region.


The results of the comparisons described above are summarized as follows:
1) In experiments Al, A2, B2, and B9, during the period within which the SWL intersects the sandy beach,

accretion occurs landward and immediately adjacent to this intersection area.

2) Initially, during the period in which the SWL intersects the seawall, the beach is entirely submerged and local

scour occurs at the seawall toe in all experiments. This occurs during the peak SWL period for experiments Al,
A2, and B2. For B9, this scour occurs in the SWL escalation period and the scour is recovered during the peak

SWL period. The recovery observed in the peak SWL period of Experiment B9 could be due to the extensive
overtopping that occurred during this phase as evidenced by the severe scour landward of the seawall.

3) Severe erosion landward of the seawall occurs when water overtops the the seawall at times of elevated SWL's.

The magnitude of this erosion increases with higher water levels and with longer time durations of these elevated

water levels due to the associated increase in total water volume overtopping the seawall.

4) At the end of Stage 4, the beach profiles exhibit little difference seaward of the seawall in each comparison.

For instance, both Al and A2 (the coarser sediment experiments) exhibit accretion out to almost 0.5 meters seaward

of the seawall, whereas, B2 and B9 (the finer sediment experiments) exhibit erosion compared to the initial profile

in this same region.




3.2 Effects of Random Waves versus Regular Waves


The effect of different wave types (regular waves versus random waves) on the model beach profile in the

vicinity of a seawall is the focus of the comparisons in this subsection. Experiment B6 (regular waves) is compared

to B7 (random waves) and experiment B8 (random waves) is compared to B9 (regular waves). Wave type is the

only experimental parameter which differs between the two experiments in each comparison. Additionally,

however, B6 and B7 were performed with Storm Surge #2 and Seawall #3 whereas B8 and B9 were performed

with Storm Surge #4 and Seawall #2.


The experimental parameters for B6 and B7 are listed in Table 6 where the shaded parameters are those

which are the same for the both experiments. Similarly, Table 7 lists the experimental parameters for B8 and B9.


- 22 -










These four experiments were performed with a model wave period of 1.65 seconds and a design wave height of 16

cm. The seawall in all cases is a simple, vertical section. The two storm surges listed in tables 6 and 7 below are

shown in figures 7 and 9. The wave spectra for the random wave experiments B7 and B8 are plotted in Figure 5.

In comparing the effects of random and regular waves, it should be recognized that by having the significant wave

height of the random waves equal to the regular wave height, according to the Rayleigh distribution, the average

height of the random waves is only 63% of that of the regular waves.


Table 6. Experimental parameters for B6 and B7 with common values shaded.


Experimental B6 B7
Parameter model prototype model prototype


peak surge [m] 0.144 3.600 0.144 3.600
wave type regular regular random random
wave period [s] 1.650 8.250 1.65) 8.250
sed. median diam. [mnru 0.090 0.210 0.090 0.210
seawall height [m] 0.199 4.975 0.199 4.975





Table 7. Experimental parameters for B8 and B9 with common values shaded.

Experimental B8 B9
Parameter model prototype model prototype


peak surge [m] 0.168 4.200 0.168 4.200
wave type random random regular regular
wave period [s] 1.650 8.250 1.650 8.250
sed. median diaim. [mm] 0.090 0.210 0.090 0.210
seawall height [m] 0.223 5.585 0.223 5.585


All of the four experiments, B6, B7, B8, and B9, were run for a total of 7.8 hours (39 hours prototype).

Profiles were measured at the end of each of the four time intervals described previously. These profiles are the

solid lines shown in Figure 16 through Figure 19. The position of the SWL at the end of each time interval is also

presented in these figures as a straight, solid line. The dotted lines in these figures are the differences in profile

elevation from the initial profile. Several general observations can be made from these figures.


- 23 -








Experiment B6, Regular Waves


0.
o.


-0.

o0.



S0

> 0.
-0.



-0.




0.:


Storm Surge #2
SWL escalation
3.6 hours elapsed (model)


SWL: 0.12m


NGVD


............
, i i J i ,


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
n in


-1.0
0.30 -

0.25 -

r 0.20
z
0.15 -

| 0.10 -

S0.05





O
S0.00 -

-0.05 -

E -0.10 -

-0.15 --


Storm Surge #2
seawall # 3 peak SWL
~i ovation 0.199m 4.2 hours elapsed (model)


SWL: 0.144m




NGVD ..... .... ........



00 i. 20 25 3




-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0
model distance from seawall metersl


2.5 3.0 3.5 4.0


Figure 16. Model beach profiles and elevation differences from the initial profile -- experiment B6.


-24-


seawall #3

elevation 0.199m


30-

25 Storm Surge #2
Seawall # 3 pre-escalation of SWL
e elevation 0.199m 3.0hours elapsed (model)





05 ...SWL: 0.036m


05 "" .......................... .. .
NOVD


05

10 -

15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
30 -.-


0
S0.25

Z 0.20

S0.15
0)



0.05

> 0.00

-0.05

-0.10

-0.15


0.25



a>
Z 0.20)




0.0
0.10

S0.0.5

> 0.03

-0.05

-0.10

-0.15


4.0


-

-

-

-

-








Experiment B7, Random Waves


0.30

S0.25

z 02'0

.0.15



0.05

> 0.00

- 0.05


0.15




-0 5
0.30




0.15
0D


0.05

> 0.00

.0

0 -0.10

.0.1.5

0.30

0.25
0.20

2 0.15

0.10

0.05

> 0.00
0.05


0 .0.10

-0.15

0.30

5 0.25
. 0.-0

0.15
U 0.20


0.05

S0,00
0)


E 4)10
.0.15


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5


Figure 17. Model beach profiles and elevation differences from the initial profile -- experiment B7.


-25-


Storm Surge #2
seawall # 3 pre-escalation of SWL
-"-elevation 0.199m 3.0hours elapsed (model)




SWL: 0.036m

NOVD
NOVD ....... ....................... .. .. .. .. .. .__ .







-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall #3 SWL escalation
elevation 0.199m 3.6 hours elapsed (model)


N DSWL: 0.12m



NGVD







-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall # 3 peak SWL
-r-elevation 0.199m 4.2 hours elapsed (model)


NSWL: 0.144m




NGVD .

-r. ....





.1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall # 3 descending SWL
S- ovation O.199m 4.8 hours elapsed (model)
~' elevation 0.199m




SWL: 0.048m

NGVD
--........... .. .... --". ..' .. .--.. ..ifference. frm.ita....... ""



--- model beach profile --........... difference from initial
u~ I I


3.0 3.5 4.0











0.30

0.25

Z 0.20

So0.15

0.10

0.05

> 0.00

.2-0.05

S.0.10

-0.15


Experiment B8, Random Waves



Storm Surge #4
--- seawall # 2 pre-escalation of SWL
elevation 0.223m 3.0 hours elapsed (model)




-SWL: 0.06m

NOVD.. .......




-.0-.0.0.101.2.2.3.354.


SStorm Surge #4
.5 seawall # 2 SWL escalation
o .20 ele a 02m 3.6 hours elapsed (model)
Z 0.20 elevation 0.223m

0.15 -
SWL: 0.144m
g .o- /.

0.05 -

0.00 N G VD ......... ...... ... ...... ... .............................................

-0.05

-0.10

-o0.15


-1.0
0.30

0 .25-

S0.20

0.15 -

0.10-

0.05-

> 0.00-

S-0.0.5 -
S0.10
0 -0.10


S0.25 -

U 0.20-
z
0.15 -

S0.10

0.05 -

0.00 -

-0.05 -
o
-. 10-

-0.15 -
-1.0


-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
model distance from seawall [meters]


Figure 18. Model beach profiles and elevation differences from the initial profile -- experiment B8.


-26-


-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


-1.0 -0.5 0.0 0.5 1.0 1.5


2.0 2.5 3.0 3.5 4.0














C5

Z





















z
1c












CO
0






















-0
c s













I(
ffl





















































0o
'0
0
(g


-1.0


-0.5 0.0 0.5 1.0 1.5 2.0
model distance from seawall [meters]


2.5 3.0 3.5 4.0


Figure 19. Model beach profiles and elevation differences from the initial profile -- experiment B9.


- 27-
-L-


Experiment B9, Regular Waves

0.30

Storm Surge #4
0.25 seawall # 2 pre-escalation of SWL

. ovation 0.223m 3.0 hours elapsed (model)
0.20 -elevation 0.223m

0.15

0.10 -
SWL: 0.06m
0.05 -

NGVD ,.


0.05

0.10 -
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 -seawall I 2 Storm Surge #4
Seaw l # 2 SWL escalation

0.21 elevation 0.223m 3.6 hours elapsed (model)

0.15 -
SWL: 0.144m
0.10 -


0.05


0.05 -


0.10
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

Storm Surge #4
0.25 seawall # 2 peak SWL

ovation 0.223m 4.2 hours elapsed (model)
0.20 elevation 0.223m

0.15 SWL: 0.168m

0.10

.05 -

NGVD..... '- /- -. ... .. .j..1.... ........

).(105 "' '"' ... ".......-.- .

0.10

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 seawall # 2 Storm Surge #4
----- descending SWL
0.20 elevation 0.223m 4.8 hours elapsed (model)

0.15

0.10
1SWL: 0.072m



NGVD ..........
0.05 -
o.oo N G V D -",.,. t ......................... ...."..... ......... ......,
..... .................- -- --- -

0.05 .............. --- model beach profile .--..-- difference from initial

0.10 I I -









The general erosive and accretive trends are similar in the four experiments. The primary observable trend

occurs at the point of intersection of the SWL with the profile and in the area immediately landward of this point.
If the SWL intersects the sand beach, local accretion occurs and there is no change in the profile landward of the

seawall. On the other hand, if the SWL intersects the seawall and the beach is totally submerged, then local scour

occurs at the seawall toe and erosion occurs landward of the seawall. The magnitude of landward erosion is greater

for higher SWL's and for longer durations of these elevated SWL's.


The elevation differences from the initial profile for experiments B6 and B7 are plotted together in Figure
20 for each of the four time intervals considered. Likewise for B8 and B9 in Figure 21. In both figures, the regular

wave experiment is plotted as the solid line and the random wave experiment is plotted as the dotted line. These

figures facility the comparison between experiments.


At the end of Stage 1, the pre-escalation phase, the SWL intersects the sandy beach in experiments B6,
B7, B8, and B9. Accretion occurs at and immediately landward of this intersection area in these four experiments.

In both comparisons, this area of accretion is concentrated over a smaller local area in the regular wave experiments

than in the random wave experiments, which produce more diffuse accretion in this vicinity. In the region between

2.5 and 3.5 meters seaward of the seawall, significant accretion occurs in the regular wave experiment B9, whereas

there is comparatively little change in this region for experiments B6, B7, and B8. Erosion occurs in all four of the

experiments in the area between the aforementioned SWL intersection point and approximately 2.5 meters seaward

of the seawall.


At the end of Stage 2, the SWL escalation phase, the SWL continues to intersect the sand beach for B7

(random waves) but this point of intersection is closer to the seawall than it was at the end of Stage 1. Figure 9

shows that the material accreted during Stage 1 migrates landward with the SWL intersection point to the Stage 2
position for B7.


At the end of Stage 2, the SWL intersects the seawall for B6, B8, and B9. The material accreted at the end

of Stage 1 for these experiments is transported seawards by the end of Stage 2. Local scour at the seawall toe for

B9 is significant. Erosion landward of the seawall also begins to occur in all of the four experiments at the end of
this time interval, but is minimal compared to that which occurs in the next time interval.


- 28-








Comparison Between B6 and B7


0.30



a0.20



0.10




-t:0.05

-0.1




0.30



0.20

E! 0.15





rcd




> -0.10



0.30



,0.20

E!0.15





0.05



0.30



O..

-0.10

S0.05

0.00


-00.1S

-0. 0
-OA


1 *0 L5 2.0
model distance from seawall [meters]


Figure 20. Elevation differences from the initial profile -- comparison between B6 and 137.


? re-escalation of SWL
cxpermient: B16 B7
SWL [m]: 0.036 0.036


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0



SWL escalation
experiment: B6 B7
seawall # 3 SWL [m]: 0.120 0.120
location












-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0



peak SWL
experiment B6 B7
seawall # 3 SWL [m]: 0.144 0.144
Location


\ ..f



r' fii


seawall #
location


A


-1.0


-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


-29-








Comparison Between B8 and B9


0.25-
.2 pre-escalation of SWL
P .20 experiment 18 B9
seawall # 2 SWL [ml: 0.060 0.060
0.15 -
location
0.10

S0.05



-0.05

> -0.10
10

-.1 .0 .5 0.0 0.5 1.0 2.0 2.5 3.0 3.5 4.0
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


U.U0

0.25 -
SWL escalation
0.20 experiment: B8 B9

05 seawall #2 SWL [m]: 0.144 0.144

0.10 -

0.05 -



-0.05 -

-0.10-

-0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 -
peak SWL
0.20 experiment: B8 B9
seawall #2 SWL [m]: 0.168 0.168
0.15 -
0.10location


0.05 -

o.o5 -

-0.05 .

-0.10-

.0.15 ,..


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
S0.30

S0.25 descending SWL
2 experiment: B8 B9
S0.20 SWL [m]: 0.072 0.072
seawall # 2
0o.15- location

0.10- .
o.o
0 0.05 -
0)
S0.00

S-0.05 -
...
0.o --- experiment B8 -.---..- experiment B9
S-0.15

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
model distance from seawall [meters]


Figure 21. Elevation differences from the initial profile -- comparison between B8 and B9.


-30-


's!

6
Co
0


I-
0)
C.5
co












0)
I-
0)
S




E







01
C.)



Co






'0
3

i



10
03









At the end of Stage 3, the peak SWL phase, the beach is submerged in all of the four experiments. Scour

at the seawall toe is experienced in B6, B7, and B8. In contrast, for Experiment B9, complete recovery occurs

from the scour occurring in this experiment at the end of the previous stage. Erosion landward of the seawall is

severe for all of the four experiments during this time interval.


At the end of Stage 4, the descending SWL phase, the beach is subaerially exposed in all of the four
experiments. There is more subaerially exposed beach however in experiments B6 and B7 than is exposed in

experiments B8 and B9 at this time due to the SWL differences but there is little corresponding difference in profile

response. In fact, the resulting profiles are very similar in all of the four experiments at the end of this time
duration.


Results of the comparisons of experiments B6, B7, B8, and B9, described above are summarized as

follows:

1) It is observed that in all of the four experiments, during periods when the SWL intersects the sand beach,

accretion occurs landward and immediately adjacent to this intersection area. Experiment B9 is one exception
however. During the descending SWL phase of experiment B9, accretion does not occur at this intersection point.
2) Initially, during the period in which the SWL intersects the seawall, the beach is entirely submerged and local

scour occurs at the seawall toe in all of the four experiments. This occurs during the peak SWL period for

experiments B6, B7, and B8. For Experiment B9, this scour occurs in the SWL escalation period and the scour

is recovered during the peak SWL period. The recovery observed in the peak SWL period of Experiment B9 could
be due to the extensive overtopping that occurred during this phase as evidenced by the severe scour landward of
the seawall.

3) Erosion landward of the seawall occurs when water overtops the the seawall at times of elevated SWL's (i.e.,

the peak SWL period). The magnitude of erosion is relatively the same for all of the four experiments.

4) At the end of Stage 4, the final profiles exhibit little difference seaward or landward of the seawall in all of

the four experiments. Relatively speaking, erosion is severe landward of the seawall and it is moderate seaward
of the seawall out to a distance of approximately 2.0 meters offshore (50 meters prototype).


Overall, from the above comparisons, it appears that wave type has little influence on the resulting profile

given the time-varying severe sea conditions modelled in the experiments. These results contrast greatly with the

results of the C-Series experiments which were run under a constant surge level (Thompson et al., 1993). This


-31 -









difference is due to the duration of the higher SWL's and the lower energy content of the random waves as
compared to the regular waves.




3.3 Sensitivity Effects of Lowered Profile


The comparisons in this subsection focus on the effect of lowering the initial model beach profile by 2.40
centimeters (0.60 meters prototype) while leaving all other experimental parameters unchanged. Specifically,

Experiment B6 (profile unchanged) is compared with B9* (lowered profile), and B7 (profile unchanged) is compared

with BS* (lowered profile). Experiments B8* and B9* are adjusted data from experiments B8 and B9, respectively.

This adjustment was performed by subtracting 2.4 centimeters from the all of the elevation data of experiments B8

and B9. Effectively lowering the initial profile in this way is identical to raising the time-varying storm surge levels
and seawall height by 2.4 centimeters. Experiments B8 and B9 were performed using Seawall #2 and Storm Surge

#4. As mentioned above, the vertical datum for the profile data in both of these experiments is adjusted by 0.024

meters to obtain B8* and B9* which correspond to experiments performed with Seawall #3 and Storm Surge #2

as were B6 and B7. Thus, initial profile elevation is the only experimental parameter which differs between the

two experiments in each comparison. In addition, B6 and B9* are regular wave experiments whereas B7 and B8*
are random wave experiments.


The experimental parameters for B6 and B9* are listed in Table 8 where the shaded parameters are those

which are the same for the both experiments. Similarly, Table 9 lists the experimental parameters for B7 and B8*.

Experiments B6 and B9* were performed with a wave period of 1.65 seconds and a deepwater wave height of 16
cm. Experiments B7 and B8* were performed with a modal period of 1.65 seconds and a significant wave height
of 16 cm in deepwater. The seawall is a simple, vertical section. The Storm Surge #2 listed in tables 8 and 9

below is presented in Figure 7. The wave spectra for the random wave experiments B7 and B8* are plotted in

Figure 5.


All four experiments, B6, B7, B8*, and B9*, were run for a total of 7.8 model hours (39 hours prototype).

Profiles were measured at the end of each of the four time intervals described previously. These profiles are the

solid lines shown in figures 22 through 25. The elevation of the SWL at the end of each time interval considered

is also presented in these figures as a straight solid line. The dotted lines in these figures are the differences in

profile elevation from the initial profile.


-32-









Table 8. Experimental parameters for B6 and B9* with common values shaded.

Experimental B6 B9*
Parameter model prototype model prototype


initial profile #1 (PAL192) (#1)-0.024m (PAL192)-0.6m
peak surge [ml 0.144 3.600 0.144 3.600
wave type regular regular regular regular
wave period [s] 1.650 8.250 1.650 8.250
deepwater wave height [ml 0.160 4.000 0.160 4.000
sed. median diam. [mnm 0.090 0.210 0.090 0.210
seawall height [m] 0.199 4.975 0.199 4.975


* Elevation data is adjusted to a vert. datum of +0.024m NGVD (+.6m proto.).

Table 9. Experimental parameters for B7 and B8* with common values shaded.
Experimental B7 B8*
Parameter model prototype model prototype


initial profile #1 PAL192 #1-0.024m PAL192-0.6m
peak surge [ml 0.144 3.600 0.144 3.600
wave type random random random random
wa'e period [s] 1.650 8.250 1.650 8.250
deepwater wave height [m] 0.160 4.000 0.160 4.000
sed. median diam. [mmin 0.090 0.210 0.090 0.210
seawall height [m] 0.199 4.975 0.199 4.975


* Elevation data is adjusted to a vert. datum of +0.024m NGVD (+.6m proto.).


The general erosive and accretive trends are similar in all of the four experiments. The primary observable

trend occurs at the point of intersection of the SWL with the profile and in the area immediately landward of this

point. If the SWL intersects the sand beach, local accretion occurs and there is no change landward of the seawall.

On the other hand, if the SWL intersects the seawall and the beach is totally submerged, then local scour occurs

at the seawall toe and erosion occurs landward of the seawall. The magnitude of landward erosion is greater for

higher SWL's and for longer durations of these elevated SWL's.


The elevation differences from the initial profile for experiments B6 and B9* (regular wave experiments)

are plotted together in Figure 26 for each of the four time intervals. Likewise for B7 and B8* (random wave


-33 -







Experiment B6, Regular Waves


Storm Surge #2
pre-escalation of SWL
3.0hours elapsed modele)


0.30
o.i


Z 0o.>

2 0.15


0


> 0.00

-0.05

0 0.10

-0.15






0 o.:o







> 0.00
0.)











0 -0.10

-0.15

0.30

0.>



S0.15

S0.10
g 0.05


> 0.00





.0.15

0.30

0.25

0.20
z
o.o


0.15
0.30









-0.05

0.00




E .0.10

-0.15
5)
t ~o
- 00
4)
0 ''


-

-

-


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall #3 SWL escalation
-elevation 0.199m 3.6 hours elapsed (model)




--
SWL: 0.12m



N.VD ---- .... ..







-1.0 .0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall # 3 peak SWL
--vation 0.199m 4.2 hours elapsed (model)
elevation 0.199m


SSWL: 0.144m




NGVD ...... .. .........
",.,.

..... .......,./,. .
model bahrf .. ier



-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall # 3 descending SWL
ovation 0.199m 4.8 hours elapsed (model)
elevation 0.199m




SWL: 0.048m

NGV D ._ ..... ...... .......... ....""" ................ ...............


--- m odel I ....l ........... '........ ....f n f i


S- model beach profile .............. difference from initial


0.0 0.5 1.0 1.5 2.0
model distance from seawall [meters]


2.5 3.0 3.5 4.0


-1.0 -0.5


seawall # 3
elevation 0.199m


Figure 22. Model beach profiles and elevation differences from the initial profile -- experiment B6.


-34-


SWL: 0.036m


I 1


NOVD


/--------








Experiment B9 Regular Waves


z

C3


E3





O









z
U,
I-1
4)


a
43








48













a4




z
u









5)

u
z






^s
5,
-3

*


-1.0 -0.5


0.0 0.5 1.0 1.5 2.0
model distance from seawall [meters]


2.5 3.0 3.5 4.0


Figure 23. Model beach profiles and elevation differences from the initial profile -- experiment B9*.


-35-


0..3

0.25 Storm Surge #2

0.2se l # 3 pre-escalation of SWL
Elevation 0.199m 3.0hours elapsed (model)
o.15

0.10 -

0.0 ........ SWL: 0.036m

0.0 NGVD


-0.01
-0.10


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.31

0.25 Storm Surge #2
seawall #3 SWL escalation
o.20- :-"elevation 0.199m 3.6 hours elapsed (model)

0.15 -

0.10 SWL: 0.12m

0.05 -

-..0. .- ............ ............. .... ................



-0.10 -

-0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.20

0.5 Storm Surge #2
seawall # 3 peak SWL
0.20- 'iievation 0.199m 4.2 hours elapsed (model)

0.15 -
o.o SWL: 0.144m



0.05 ........... .........
0.05 -
NGVD -. --..........




-0.10 5'...
-0.10

.0.15 ,-------- i -- ,-- -- --, --,
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 Storm Surge #2
seawall # 3 descending SWL
0.20-evan 199m 4.8 hours elapsed (model)
elevation 0.199m
0.15 -

0.10
SWL: 0.048m
0.05 -
NGVD
0.00 -

.0.05 .
.0 5 ................... ".... .

.0.10 -- model beach profile .............. difference from initial

-0.15 -







Experiment B7, Random Waves


0.25

Z 0.20

S0.15

so.o
0.10

0.05

> 0.00

4 -0.05
0)
S-.10

-0.15


0


z


0
2
S)




0

0)
S
a
0)
i)
0


-1.0 -0.5 0.0 0.5


1.0 1.5 2.0 2.5 3.0 3.5


Figure 24. Model beach profiles and elevation differences from the initial profile -- experiment B7.


-36-


0.30-

0.25 seawall #3 Storm Surge #2
SWL escalation
0.20 -- elevationn 0.199m 3.6 hours elapsed (model)

0.15 -

0.10 SWL: 0.12m

0.05 -
NGVD
0..oo N V......
-0.05 -

-0.10

-0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30-

0.25 -Storm Surge #2
seawall # 3 peak SWL
0.20 -elevation 0.199m 4.2 hours elapsed (model)

0.15 -----
S-SWL: 0.144m
0.10


NGVD
0.0 )0 .......------ ....... .---------- .........--- ----



0.10

-0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 Storm Surge #2
seawall # 3 descending SWL
0.20 -" ovation 0.199m 4.8 hours elapsed (model)


0.10

SWL: 0.048m
0.05
NGVD
0.(15 "- ..........----------------"---------------

0.05 -

0.10 model beach profile -*-....... difference from initial

0.15


03


z
CU

I-
0a


















0
0)
I-
0)
03

U3

0








Experiment B8, Random Waves


0... -

0.25 -

0.) -

0.15 -

0.10 -

0.05 -


Storm Surge #2
pre-escalation of SWL
3.0hours elapsed (model)


>

C,
Z

4)
S
4)

0


4>
4




4)





0c





o
z











I-
2
4)
4)
1


(3
0

4a

o
4)




C3





z
I-


4)
u

2


o

a
0

4)
4)
4)

a".


NOVD


0.05
.os
0.10 -

0.15
-1.0 .0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 Storm Surge #2
seawall #3 SWL escalation
0.120- n e~levation 0.199m 3.6 hours elapsed (model)

0.15 -

0.10- SWL: 0.12m

0.05 -



0.05

0.1(1

0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 Storm Surge #2
seawall # 3 peak SWL
0.20 '-a elevation 0.199m 4.2 hours elapsed (model)

0.15
-SWL: 0.144m
0.10

0.05 -

o.co NGVD ..........-.............


0.05 -

0.10-


00.15 .0.0, 1. 1. 2. 2.5-


0.30

S0.25
0.20
z
0.15

S0.10

0.05
0.00
4.o

S-0.05
0
E -0.t0

-0.15


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
model distance from seawall [meters]



Figure 25. Model beach profiles and elevation differences from the initial profile -- experiment B8*.



-37-


seawall # 3
elevation 0.199m


SWL: 0.036m


...........


1.0


Storm Surge #2
seawall # 3 descending SWL
-- 1m 4.8 hours elapsed (model)
elevation 0.199m



SWL: 0.048m


NGVD-.... .

-NGVD-- model beach pro-. d e fm i .......................


.-.. model beach profile ----.......... difference from initial


-0.5 0.0


- - - - - - -


0.5 1.0 1.5


2.0 2.5









experiments) in Figure 27. In each figure, the experiment with the unchanged initial profile is plotted as the solid

line and the experiment with the lowered initial profile is plotted as the dotted line.


At the end of Stage 1, the pre-escalation phase, the SWL intersects the sand beach in experiments B6,
B7, B8*, and B9*. Accretion occurs at and immediately landward of this intersection area in all of the four

experiments. In both comparisons, this area of accretion is more concentrated over a smaller local area in the

regular wave experiments than in the random wave experiments which produce more diffuse accretion in this

vicinity. As well, in the region between 2.5 and 3.5 meters seaward of the seawall, significant accretion occurs

in the regular wave experiment B9*. There is comparatively little change in this region for the remaining three
experiments. Erosion occurs in all four experiments in the area between the aforementioned SWL intersection point

and approximately 2.5 meters seaward of the seawall.


At the end of Stage 2, the SWL escalation phase, the SWL continues to intersect the sand beach for B7

(unchanged profile, random waves) but this point of intersection is closer to the seawall than it was at the end of

Stage 1. Figure 27 shows that the material accreted during Stage 1 migrates landward with the SWL intersection
point to the Stage 2 position for B7.


For B6, B8*, and B9*, the SWL intersects the seawall at the end of Stage 2. The material accreted at the

end of Stage 1 for these experiments is transported offshore by the end of Stage 2. Local scour at the seawall toe

for B9*, the lowered-profile regular wave experiment, is significant. Erosion landward of the seawall also begins
to occur in all four experiments at the end of Stage 2, but is minimal compared to that which occurs in Stage 3.


During Stage 3, the peak SWL phase, the beach is submerged in all of the four experiments. Scour at

the seawall toe occurs experiments B6, B7, and B8*. Experiment B9* experiences complete recovery from the

scour which occurred at the end of the previous stage. Erosion landward of the seawall is severe for all of the four
experiments.


At the end of Stage 4, the descending SWL phase, the beach is subaerially exposed in all of the four

experiments. More beach is subaerially exposed however in experiments B6 and B7 than is subaerially exposed

in B8* and B9* due to the lowered initial profile in the latter two experiments. There is little corresponding

difference in profile response, however. In fact, the resulting profiles are very similar in all of the four
experiments, indicating little sensitivity to uniform profile changes.


- 38 -







Comparison Between B6 and B9


0.30

0.23
"s pre-escalation of SWL
S0.2 experiment: B6 BY
seawall # 3 SWL [m]: 0.036 0.036
E 0.15 -
0 location
S0.10

0.05 y
o......".. ... ..-.. .. ......



-0.05-

-0.10 -

-0.15
1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


0

4)

C)


CO


U.3o

0.25-
SWL escalation
0.20 experiment: B6 B9

0.15 seawall # 3 SWL [m]: 0.120 0.120
.10 location
0.10 -

0.05-



-0.05 -

-0.10 -

-0.15


.-, 0.30

S0.25 descending SWL
Experiment: B6 B9*
S0.20 SWL [m]: 0.048 0.048
E -seawall # 3
S0.15 -location

0.10 -

S0.05

0.0 """

" -0.05 ....... .

-o -- experiment B6 -...... experiment B9*

. -0. 5
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
model distance from seawall [meters]

Figure 26. Elevation differences from the initial profile for regular wave experiments. Comparison between

B6 (original elevation) and B9* (lowered elevation).


-39-


3.5 4.0


1.0 1.5 2.0 2.5 3.0


-1.0 -0.5 0.0 0.5






Comparison Between B7 and B8 *


0.30 -


0.25

0.20

0.15
o
0.10

0.05


I-OL
a-0.05

S4-0.10

-0.15


0i

4)a
U2
4)
I-
4)



0


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0
model distance from seawall [meters]


2.5 3.0


3.5 4.0


Figure 27. Elevation differences from the initial profile for random wave experiments. Comparison between

B7 (original elevation) and B8* (lowered elevation).


-40-


1 I I--


pre-escalation of SWL
experiment: B7 BS*
seawall # 3 SWL [m]: 0.036 0.036
location



S.................. ........


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


0.25-

0.20 SWL escalation
experiment: B7 B8*

0.15 seawall # 3 SWL [m]: 0.120 0.120
Location
0.10-

0.05 -



-0.05 -

-0.10 -

-0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.
0.30-

0.25 -
peak SWL
0.20 experiment: B7 B8*
seawall #3 SWL [m]: 0.144 0.144

0.10 -
location

0.05 -



0.05 -


-0.10


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.1
0.30

0.25 descending SWL
0.2 experiment: B7 B8
seawall # SWL [m]: 0.048 0.048
seawall # 3


0.10-

0.05

0.00 .

0.05 -

0.10o experiment B7 ....---.. experiment B8*

0.15


0

o
4-1




a4
S
4)


o


Z
-4



0






cO



0
I-
.'a


4)

"


i4
I3
43)

05
Cu
4)


-

-

-


-1.0 -0.5 0.0


0.5 1.0


1.5 2.0 2.5 3.0 3.5 4.0









In summary, from the above comparisons, it appears that lowering the initial profile by 2.40 centimeters

(0.6 meters prototype) has little influence on the profile evolution given the time-varying severe sea conditions

modelled in the experiments. Also as was found in the comparisons presented in the previous subsection 3.2,

different wave type (regular versus random) does not significantly influence the final model beach profile. However,

this conclusion must be considered in light of the smaller energy content of the random waves.




3.4 Profile Evolution Sensitivity Due to Energy Level of Random Waves


The effect of lowering the wave energy while leaving all other experimental parameters unchanged is the

focus of the comparisons in this subsection. Specifically, B5 is compared to B7, both random wave experiments.

B5 was performed with a 15 cm deepwater significant wave height whereas B6 was performed with a 16 cm

deepwater significant wave height. Wave energy is the only experimental parameter which differs between these

two experiments.


The experimental parameters for B5 and B7 are listed in Table 10 where the shaded parameters are those

which are the same for the both experiments. Both experiments were performed with a modal wave period of 1.65

seconds. The seawall in all cases is a simple, vertical section. The Storm Surge #2 listed in Table 10 below is

presented in Figure 7. The spectral densities for B5 and B7 are plotted in Figure 4.


Table 10. Experimental parameters for B5 and B7 with common values shaded.


-41 -


Experimental B5_ B7
Parameter model prototype model prototype


peak surge [m] 0.144 3.600 0.144 3.600
wave type random random random random
wave period [s] 1.650 8.250 1.650 8.250
deepwater wave height [m] 0.150 3.500 0.160 4.000
sed. median diam. [mm] 0.090 0.210 0.090 0.210
seawall height [m] 0.199 4.975 0.199 4.975











Experiments B5 and B7 were run for a total of 7.8 hours (39 hours prototype). Profiles were measured at

the end of each of the four time intervals described previously. These profiles are the solid lines shown in figures

28 and 29. The position of the SWL at the end of each time period is also presented in these figures as a solid,

straight line. The dotted lines in these figures are the differences in profile elevation from the initial profile.


The general erosive and accretive trends are similar in both experiments. The primary observable trend

occurs at the point of intersection of the SWL with the profile and in the area immediately landward of this point.

If the SWL intersects the movable sand beach, local accretion occurs and there is no change landward of the seawall.

On the otherhand, if the SWL intersects the seawall and the beach is totally submerged, then local scour occurs at

the seawall toe and erosion occurs landward of the seawall in magnitudes proportional to the SWL elevation and the

time duration of this elevated SWL.


The elevation differences from the initial profile for experiments B5 and B7 are plotted together in Figure

30 for each of the four time intervals: the pre-escalation, escalation, peak, and defending stages. In this figure, the

lower wave energy experiment, B5, is plotted as the solid line and the higher wave energy experiment, B7, is plotted

as the dotted line.


At the end of Stage 1, the pre-escalation phase, the SWL intersects the sand beach in both experiments.

Accretion occurs at and immediately landward of this intersection area in both experiments. As well, in the region

between 2.5 and 3.5 meters seaward of the seawall, there is comparatively little change in the profile from initial

for both experiments. Erosion occurs in both experiments in the area between the aforementioned SWL intersection

point and approximately 2.5 meters seaward of the seawall.


At the end of Stage 2, the SWL escalation phase, the SWL continues to intersect the movable sand beach

for both experiments but this point of intersection is closer to the seawall than it was at the end of Stage 1. Figure

7 shows that the material accreted during Stage 1 migrates landward with the SWL intersection point to the Stage

2 position for the experiments.


At the end of Stage 3, the peak SWL phase, the SWL intersects the seawall and the beach is submerged

in both experiments. Scour at the seawall toe is experienced in both, but the magnitude of this scour is greater for

the lower energy experiment B5. Erosion landward of the seawall is severe for the higher energy experiment B7


-42-








Experiment B5, Random Waves


z

























0













0

0
U,



























Z0
al

> .0







I0




















0-0
a





-0
.2
4o
I.
















E 4
4











.4
ZC

















a
0





-o


0-

.4


0.0 0.5 1.0


1.5 2.0 2.5 3.0 3.5 4.0


-1.0 -0.5


Figure 28. Model beach profiles and elevation differences from the initial profile -- experiment B5, Hs=15cm.


-43-


U.JO.

0.25 -
seawall # 3 Storm Surge #2
0.20- ----pre-escalation of SWL
elevation 0.199m 3.0hours elapsed (model)
0.15 -



0.05 SWL: 0.036m

NOGVD
0.00 N O V D ....................... ....... .... ....... ..........-*..... -... ...........

0.05

0.10 -

0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 Storm Surge #2
seawall #3 SWL escalation
.20vation 0.199m 3.6 hours elapsed (model)

0.15

0.10- SWL: 0.12m

0.05

NOVD
0.00 N ... -

0.05

0.10


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
.30

.25 Storm Surge #2
seawall # 3 peak SWL
.20- :i-elevation 0.199m 4.2 hours elapsed (model)

.15 -
SWL: 0.144m
1.10-



NGVDV

.05

.10 -

.15 -
.1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.30

0.25 Storm Surge #2
seawall # 3 descending SWL
0.20- eevation 0. 199m 4.8 hours elapsed (model)

0.15 -

0.10 -
SWL: 0.048m
0.05 -

0.00 NGVD.... ................ ... .

.0.5

3.10

3.15 ,, ,








Experiment B7, Random Waves


0.25

z 0.20
o.n


0.15

S0.10

0.05

> 0.00

-0.05

o .0.10

-0.15

0.30

0.25

Z 0.20

0.15

0.10





0 o.15
0












0.30
p 0.205






0.10







Z 0.00
o;





.2 .0.05
o.sa











0 .0.10
.0.15

0.30












0.25
0 0.20








z
0.15



g 0.05
S0.00
S-

















- -0.05
0
0 -010
-0.15
0.30


Storm Surge #2
pre-escalation of SWL
3.0hours elapsed (model)


NGVD


.. .. .. ... .. ...... .......


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall #3 SWL escalation
S elevation 0.199m 3.6 hours elapsed (model)



SSWL: 0.12m


NOVD







-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall # 3 peak SWL
-eievation 0.199m 4.2 hours elapsed (model)


SWL: 0.144m



NGVD







-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Storm Surge #2
seawall # 3 descending SWL
3 ovation 0.199m 4.8 hours elapsed (model)
elevation 0.199m
-I



SWL: 0.048m

NGVD
........ ...... .... ..... ..... ..... ........................



-- model beach profile .--*. difference from initial

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Figure 29. Model beach profiles and elevation differences from the initial profile -- experiment B7, Hs=16cm.


-44-


seawall # 3
elevation 0.199m


1


SWL: 0.036m


--- ------- .................
............








Comparison Between B5 and B7


pre-cscalation of SWL
experiment: 115 B7
SWL [ml: 0.036 0.036


0.30


0.25
CO


S0.15

0.10
o

S0.05

t. 0.00

-0.05

-0.10

-0.15

0.30

0.25



0.15

0.10
0.05
0
g 0.05



d -0.05

> -0.10
I-


-0.15

0.30

4 0.25



. 0.15
0
0.10

0.05
42


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0





SWL escalation

seawall # 3 experiment: B5 B7
lcatin SWL [m]: 0.120 0.120
1 location
-

-









-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


0 .00 ............................. .


-0.05 "-
-0.10 -


0.25 descending SWL
experiment: B5 B7
0.2 SWL [m]: 0.048 0.048
seawall # 3
0.15 location
o I
0.10 -

0.05


S-0.00 '" -- .... ....... ...........


S-.0 -o -- experiment B5 .... experiment B7

4 -0.15
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
model distance from seawall [mctersl


Figure 30. Elevation differences from the initial profile -- comparison between B5 and B7.


-45-


sewall # 3
Location


d


peak SWL
experiment: B5 B7
SWL [m]: 0.144 0.144


seawall # 3
/ location

r~~i


C
0
4


o

a3


2.5 3.0 3.5 4.0


-0.5 0.0 0.5 1.0 1.5 2.0


I I --- ------


-

-

-

-

-










and moderate for the lower energy experiment B5. The material accreted in front of the seawall at the end of Stage

2 for these experiments is transported offshore by the end of Stage 3.


At the end of Stage 4, the descending SWL phase, the beach is subaerially exposed in both experiments.
The resulting profiles are very similar in shape for both experiments. Experiment B5 (the lower energy experi-

ment), however, experienced less erosion relative to B7 over the entire length of the profile. As expected, there

was considerably greater scour landward of the seawall for the larger wave energy experiment.


The results of the comparisons described above are summarized as follows:
1) In experiments B5 and B7 during the time in which the SWL intersects the sand beach, accretion occurs

landward and immediately adjacent to this intersection area.

2) During the time when the SWL intersects the seawall, the beach is entirely submerged and local scour at the
seawall toe occurs in both experiments.
3) Erosion landward of the seawall occurs when water overtops the seawall during the peak SWL period. The
magnitude of erosion is greater for the higher wave energy experiment, B7.
4) At the end of Stage 4, the final profiles exhibit little difference seaward of the seawall in both experiments

(Figure 30). Relatively speaking, severe erosion is experienced landward of the seawall for B7 (the higher energy

experiment) and moderate erosion occurs for B5 (the lower energy experiment).
5) Seaward of the seawall, B5 (the lower energy experiment) experiences relatively less erosion over the entire
length of the profile as compared to B7 (the higher energy experiment).


Overall, from the above discussion, it appears that wave energy influences the resulting profile with the

greatest effect occurring as a result of the larger wave heights and the associated increased overtopping.




3.5 Summary


In this report, the results of beach model responses from the conducted experiments of Al, A2, B2, B6,

B7, B8, and B9 were compared to evaluate the following effects: (1) different storm surge condition, (2) different

wave types (regular versus random waves), (3) lowering the initial beach profile, and (4) lowering the energy
content level of random waves. The comparisons were made at four selected time intervals as the Stage 1, Stage


-46-









2, Stage 3, and Stage 4 periods, which are corresponding, respectively, to the pre-escalation period of surge water
level (SWL), the escalation period of SWL, the peak SWL period, and the descending SWL period.


The effects of using two different storm surge conditions in experiments are evaluated by comparing the
experimental results from Al to A2 (coarse sand models), and B2 to B9 (fine sand models). The two different
surge conditions employed have the similar shape but different surge elevations during the peak SWL period. The
peak surge level in model is 14.4 cm ( m in prototype) for Al and B2, and is 16.8 cm ( m in prototype) in A2 and
B9. The sand erosion landward of seawall is seen to be more severe during larger surge peak period while the

erosion seaward of seawall is mild, in general, and the beach response patterns are similar from these experiments

using the two different storm surge conditions.


The effects of using regular waves versus random waves are evaluated by comparing the experimental
results of B6 to B7, and B8 to B9. Both B6 and B9 are the regular wave experiments, whereas B7 and B8 are the

random wave experiments. In these experiments, both the deepwater wave height of regular waves and significant

height of random waves are equal to 17cm ( m in prototype). Based on the profile responses from the experiments,
the effects due to using regular waves versus random waves were found to be insignificant. The only drastic
difference in the profile responses is in a nearshore region between 2.5m and 3.5m (62.5m and 87.5m in prototype)
where significant accretion of sediment occurs in the regular wave experiments but little change of profile in this

region for the random wave experiments.


The effects of lowering the initial beach profile are examined by comparing the model results from B6 to
B9* (regular wave experiments), and B7 to B8* (random wave experiments). Here, the initial profiles of B9* and
B8* are 0.44cm ( m in prototype) lower than these of B6 and B7. A similar significant erosive trend and a mild

scour pattern were seen landward and seaward, respectively, of the seawall in all of these four experiments.

However, more erosion immediately behind the seawall is observed for the lowered profile experiment of B8* under
random waves than the unlowered profile experiment of B7 under random waves.


For the random waves with slightly differences in energy content level, the influences to the model profile
responses were investigated by comparing the experimental results between B5 and B7. The deepwater significant
wave heights measured in B5 and B7 experiments are equal to 15cm and 16cm, respectively. Severe erosion

landward of seawall occurs during the peak surge period. The magnitude of this erosion is seen to be greater for


-47-










the higher wave energy content experiment B7 than the small wave energy experiment B5. The effect of lowering

wave energy level in random waves to the beach profile seaward of seawall is found to be small.






4.0 REFERENCES


Dean, R.G., T.Y. Chiu, and S.Y. Wang, 1992. Combined total storm tide frequency analysis for Palm Beach

County, Florida, Division of Beaches and Shores, Department of Natural Resources, 58pp.


Thompson, L.L., L. Lin, and R.G. Dean, 1993. Evaluation study and comparison of erosion models and effects

of seawalls for the CCCL, Physical Modelling Program Report -- Interim Report #1. COEL -94/002,

University of Florida, Gainesville, Florida, 19pp.


-48-










and moderate for the lower energy experiment B5. The material accreted in front of the seawall at the end of Stage

2 for these experiments is transported offshore by the end of Stage 3.


At the end of Stage 4, the descending SWL phase, the beach is subaerially exposed in both experiments.
The resulting profiles are very similar in shape for both experiments. Experiment B5 (the lower energy experi-

ment), however, experienced less erosion relative to B7 over the entire length of the profile. As expected, there

was considerably greater scour landward of the seawall for the larger wave energy experiment.


The results of the comparisons described above are summarized as follows:
1) In experiments B5 and B7 during the time in which the SWL intersects the sand beach, accretion occurs

landward and immediately adjacent to this intersection area.

2) During the time when the SWL intersects the seawall, the beach is entirely submerged and local scour at the
seawall toe occurs in both experiments.
3) Erosion landward of the seawall occurs when water overtops the seawall during the peak SWL period. The
magnitude of erosion is greater for the higher wave energy experiment, B7.
4) At the end of Stage 4, the final profiles exhibit little difference seaward of the seawall in both experiments

(Figure 30). Relatively speaking, severe erosion is experienced landward of the seawall for B7 (the higher energy

experiment) and moderate erosion occurs for B5 (the lower energy experiment).
5) Seaward of the seawall, B5 (the lower energy experiment) experiences relatively less erosion over the entire
length of the profile as compared to B7 (the higher energy experiment).


Overall, from the above discussion, it appears that wave energy influences the resulting profile with the

greatest effect occurring as a result of the larger wave heights and the associated increased overtopping.




3.5 Summary


In this report, the results of beach model responses from the conducted experiments of Al, A2, B2, B6,

B7, B8, and B9 were compared to evaluate the following effects: (1) different storm surge condition, (2) different

wave types (regular versus random waves), (3) lowering the initial beach profile, and (4) lowering the energy
content level of random waves. The comparisons were made at four selected time intervals as the Stage 1, Stage


-46-










the higher wave energy content experiment B7 than the small wave energy experiment B5. The effect of lowering

wave energy level in random waves to the beach profile seaward of seawall is found to be small.






4.0 REFERENCES


Dean, R.G., T.Y. Chiu, and S.Y. Wang, 1992. Combined total storm tide frequency analysis for Palm Beach

County, Florida, Division of Beaches and Shores, Department of Natural Resources, 58pp.


Thompson, L.L., L. Lin, and R.G. Dean, 1993. Evaluation study and comparison of erosion models and effects

of seawalls for the CCCL, Physical Modelling Program Report -- Interim Report #1. COEL -94/002,

University of Florida, Gainesville, Florida, 19pp.


-48-




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