• TABLE OF CONTENTS
HIDE
 Front Cover
 Interim Report #1
 Scope of the report and Experimental...
 Comparison of Experiments A2 and...
 Summary
 References
 Wave tank experiment Series A2
 Comparison between series A2 and...
 Interim Report #2
 Scope and Experimental Conditi...
 Comparison of Series C Experim...
 Summary
 References
 Figure 13. Sand-level fluctuat...






Group Title: UFL/COEL (University of Florida. Coastal and Oceanographic Engineering Laboratory); 94/002
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/UF00084997/00001
 Material Information
Title: Evaluation study and comparison of erosion models and effects of seawalls for coastal construction control line task 3, generic modelling of seawall overtopping and associated scour : interim reports 1 and 2
Series Title: UFLCOEL-94002
Alternate Title: Task 3, generic modelling of seawall overtopping and associated scour
Generic modelling of seawall overtopping and associated scour
Physical Description: 17, 19 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 )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Lynda Thompson, Lihwa Lin, and R.G. Dean ; prepared for Department of Environmental Protection, State of Florida.
General Note: Cover title.
General Note: "January 10, 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: UF00084997
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 31795718

Table of Contents
    Front Cover
        Front Cover
    Interim Report #1
        Unnumbered ( 2 )
    Scope of the report and Experimental Conditions
        R1 - 1
        R1 - 2
        R1 - 3
        R1 - 4
        R1 - 5
        R1 - 6
        R1 - 7
        R1 - 8
    Comparison of Experiments A2 and B1
        R1 - 9
        R1 - 10
    Summary
        R1 - 10
        R1 - 11
    References
        R1 - 11
    Wave tank experiment Series A2
        R1 - 12
        R1 - 13
        R1 - 14
    Comparison between series A2 and B1
        R1 - 15
        R1 - 16
        R1 - 17
        R1 - 18
    Interim Report #2
        R2
    Scope and Experimental Conditions
        R2 - 1
        R2 - 2
        R2 - 3
        R2 - 4
        R2 - 5
        R2 - 6
    Comparison of Series C Experiments
        R2 - 7
        R2 - 8
        R2 - 9
        R2 - 10
        R2 - 6
        R2 - 11
        R2 - 12
        R2 - 13
        R2 - 14
        R2 - 15
        R2 - 16
    Summary
        R2 - 17
        R2 - 18
        R2 - 16
    References
        R2 - 18
    Figure 13. Sand-level fluctuations
        R2 - 19
Full Text




UFL/COEL-94/003


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




Task 3
Generic Modelling of Seawall Overtopping and Associated
Scour: Interim Reports 1 and 2

by

Lynda Thompson
Lihwa Lin
and
R.G. Dean


January 10, 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 #1


prepared by the
Coastal and Oceanographic Engineering Department
University of Florida
Gainesville, Florida


November 11, 1993


I














1. SCOPE OF THIS REPORT


This report summarizes the progress of wave tank experiments recently performed at University
of Florida's Coastal and Oceanographic Engineering Laboratory facilities in Gainesville, Florida. These
experiments were performed in accordance with the objectives of Tasks 2 and 3 of the DNR study of the
same title as this report. Table 1 provides a summary of the wave tank experiments completed to date
as well as those experiments that are planned in the near future. The various experimental parameters
listed in Table 1 are described in section two of this report. Ten separate experiments are listed in Table
1. Of these, experiments Al, A2, A3, A4, Bl, and B2 have been completed and experiments B3, B4,
B5, and B6 are projected to be completed within the next five weeks.
Several comparisons can be made among the experiments so far completed. However, this report
will focus on one comparison, namely the effects of varying sediment size observed by comparing
experiments A2 and Bl, which only differ in that parameter. This comparison is presented in section
three of this report. Future reports will deal with other comparisons as interest dictates and time allows.



2. 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 spectral
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 other end
of the wave tank where the model beach is located.










Table 1. Summary of experimental cases and test parameters.


water level characteristics seawall characteristics sediment wave characteristics water
initial stepwise varying straight, vertical median wave type deep water wave volume
Experiment profile storm surge model elevation diameter regular random wind wave height period overtopping
Series model peak level [cm] [cm] [mm] waves waves waves [cm] [s] seawall
14.4 16.8 21.12 22.34 19.90 0.18 0.09 16.0 14.0 1.65 measured
#1 #1 #2 #3 #1 #2 #3 #1 #2 #1 #2 #3 #1 #2 #1


Al X X X X X X X
A2 X X X X X X X
A3 X X X X X X X X
A4 X X X X X X X X X



B1 X X X X X X X
B2 X X X X X X X
B3 O O O O O O O O
B4 O O O O O O O O
B5 O O O 0 0 0 0 0
B6 O O O 00 O O O


0: not yet completed; X: completed
















qEV. (IY


V6wC


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
referred to the DNR vertical datum of NGVD. These surveys were conducted at model time increments
of 36 minutes corresponding to 180 minutes in the prototype.
Two capacitance type wave gages were installed in the tank for monitoring waves. Gage 1 is
located 18.3 meters seaward of the seawall and gage 2 is located 5.3 meters seaward of the seawall.
The volume of water overtopping the seawall during some experiments is measured by collecting
the water in a movable catch pan located immediately landward of the seawall.


2.2 Scaling
A model to prototype length scale ratio of 1:25 and time scale ratio of 1:5 were 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. All dimensions in this report are
given in model units unless otherwise stated. The rest of the parameters listed in Table 1 will be
explained in the following subsections.


2.3 Initial Profile and Seawall Configuration
The initial profile for all experiments listed in Table 1 as initial profile #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. Figure 2 shows the modelled section as compared to the entire profile. A
prototype depth of 6 meters is sufficient for purposes of this study. This particular profile has a rock
outcrop located at a prototype depth of approximately 2.5 meters.
There are three straight, vertical seawalls listed in Table 1. The first one, Seawall #1, is
modelled after the actual seawall located at R-192 which has an elevation of 5.28 meters (prototype).
Seawall #2 is identical to the first except for an elevation of 0.305 meters (prototype) higher than Seawall
#1, whereas Seawall #3 has an elevation 0.305 meters (prototype) lower than #1.

















































model distance from seawall [meters]


- DNR R-192 initial profile #1


Figure 2. Initial profile #1 versus DNR Range R-192 in Palm Beach County.

5












2.4 Storm Surge
The severe sea conditions to be physically modelled are numerically determined combined total
storm tides (Dean et al., 1992). These total storm tides include storm surges, astronomical tide, and
dynamic wave set-up which occurs primarily in the inner surf zone (landward of wave breaking). These
time-varying total storm tide profiles are physically modelled in the wave tank by raising the water level
in a step-wise fashion. Figure 3 shows the relation between the continuous storm surge profile of the
prototype and the stepped simulation used in the model.
At each step, the waves are generated for the run duration (in model time-units) for that particular
step or increment of time in the storm tide profile. At the end of each run, the beach profile is measured
while the water level is adjusted to the appropriate level for the next step. This procedure is followed,
starting from an initial beach profile with water level at zero vertical datum (NGVD), then raising the
water level in steps as shown in Figure 3, and ending with a final run with water level again at vertical
datum. The intermittent beach profile measurements during this stepwise procedure allow for the
evaluation of seawall performance and profile adjustment during the storm escalation as well as the beach
recovery periods of a typical severe storm.


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 sediment-size distributions for each
of these sediments are shown in Figure 4. The effect of these two sizes on the model profile response
will be discussed in the next section of this report.


2.6 Wave Conditions
Testing to date has been conducted with regular waves with a height of 0.15 meters. This
corresponds to a protype wave height of 3.8 meters. The model wave period listed in Table 1 as wave
period #1 is 1.65 seconds in the model which corresponds to a prototype value of 8.25 seconds.
















































15 20 25 30
prototype time [hrs = 36 model minutes]


prototype model


Figure 3. Continuous prototype and stepwise model storm surge profiles.

7




























SAND SIZE DISTRIBUTION


1.00

0.00
-- coarse sand
0.80 ----- fine sand

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90

D (mm)











Figure 4. Cumulative grain-size distributions for model sands #1 and #2.









COMPARISON OF EXPERIMENTS A2 AND B1


Experiments A2 and B1 are chosen for comparison to demonstrate the effects of varying sediment
size in the beach model. All experimental parameters for these two studies were the same except for the
sediment size of the model beach (see Table 2). As noted previously, the median sediment diameters for
A2 and B1 are 0.18 and 0.09 mm, respectively. Throughout this discussion, A2 will also be referred
to as the coarse-sediment profile and B1 as the fine-sediment profile.
Table 2. Experimental parameters for experiments A2 and Bl.

Experimental A2 B1
Parameter model prototype model prototype

peak surge [mI 0.168 4.200 0.168 4.200
wave type regular regular regular regular
wave period [s] 1.650 8.250 1.650 8.250
sed. median diam. [mm] 0.180 0.650 0.090 0.210
seawall height [m] 0.223 5.585 0.223 5.585



Figure 5a and 5b show the observed wave height at Gage 1 and 2 for each storm-surge step in
Experiments A2 and B1, respectively. As shown in these figures, the wave heights for A2 and B1 are
quite similar. Also note the position of the surge elevation during model times 216, 252, and 288
minutes. These times correspond to the following critical conditions:
1) 216 minutes elapsed: just prior to water level reaching the seawall toe,
2) 252 minutes elapsed: surge elevation is at a maximum and beach profile scour at the seawall
toe reaches the maximum for A2, and
3) 288 minutes elapsed: surge elevation is at a maximum and beach profile scour at the seawall
toe reaches the maximum for Bl.
Profile responses at 0, 216 and 218 minutes are shown in Figures 6a and 6b for A2 and B1, respectively.
These figures show the relative positions of the profiles at the selected times for each experiment. The
profile response "envelope" or elevation maxima and minima for all times measured is shown in Figures
7a and 7b for Al and B2, respectively. Notable in Figure 7 is the slightly wider envelope of the finer-
sediment profile, especially for the subaerial beach portion.
Figures 8, 9 and 10 compare A2 and B1 at each of the selected times mentioned above. Figures
8a, 9a, and 10a compare the actual measured model profiles. Figures 8b, 9b, and 10b compare the









profile change relative to the initial profile for both experiments. At time 216 minutes elapsed, Figure
8 shows a similar pattern of erosion and accretion in the beach and nearshore area out to a model distance
of 3 meters seaward of the seawall. At time 252 minutes elapsed, Figure 9 shows the same similar trend
as shown in Figure 8, except for the area immediately in front of the seawall where the coarse-sediment
profile shows accretion while the fine-sediment profile indicates erosion. At time 288 minutes elapsed,
Figure 10 also shows a similar general trend of erosion and accretion out to a model distance of 3 meters
from the seawall. At this time, both A2 and B1 show a similar maximum model erosion of 0.06 to 0.07
meters, which corresponds to a prototype value of 1.5 to 1.75 meters relative to the initial profile.
From examination of Figures 8, 9, and 10, it is clear that the major difference in profile behavior
between A2 and B1 occurs at the seawall toe. Figure 11 presents the time history of sand level at the
toe of the seawall for both A2 and Bl. In comparison between A2 and Bl, the most notable difference
occurs after peak surge elevation where the coarse-sediment profile indicates recovery and actual accretion
after the storm and the fine-sediment profile shows no sign of recovery and actual erosion after the storm.
In general, both A2 and B1 profiles experience a similar accretionary trend just prior to peak surge levels.




SUMMARY


A series of physical modelling experiments is in progress at the Coastal and Oceanographic
Engineering Laboratory at the University of Florida. The performed experiments aim at investigating
the interaction between the seawall and beach profile in the area adjacent to the seawall in both landward
and seaward directions. Six experiments have been completed to date. This report compares the
experimental results from two of the experiments, namely A2 and Bl. These two were performed under
identical storm surge and wave conditions. The only parameter which was varied between A2 and B1
was the sediment size. The coarse-sediment profile is A2 and the fine-sediment profile is Bl.
The results of the comparison between A2 and B1 can be summarized as follows:
1) A general seaward sediment transport trend was observed in both experiments.
2) Similar accretionary trends occurred in both experiments in front of the seawall ( between 0 and 0.5
meters) prior to peak storm surge elevation.
3) At peak storm surge elevation both experiments experienced erosion. However, this erosional trend
occurred about 36 minutes earlier in Bl than in A2.









profile change relative to the initial profile for both experiments. At time 216 minutes elapsed, Figure
8 shows a similar pattern of erosion and accretion in the beach and nearshore area out to a model distance
of 3 meters seaward of the seawall. At time 252 minutes elapsed, Figure 9 shows the same similar trend
as shown in Figure 8, except for the area immediately in front of the seawall where the coarse-sediment
profile shows accretion while the fine-sediment profile indicates erosion. At time 288 minutes elapsed,
Figure 10 also shows a similar general trend of erosion and accretion out to a model distance of 3 meters
from the seawall. At this time, both A2 and B1 show a similar maximum model erosion of 0.06 to 0.07
meters, which corresponds to a prototype value of 1.5 to 1.75 meters relative to the initial profile.
From examination of Figures 8, 9, and 10, it is clear that the major difference in profile behavior
between A2 and B1 occurs at the seawall toe. Figure 11 presents the time history of sand level at the
toe of the seawall for both A2 and Bl. In comparison between A2 and Bl, the most notable difference
occurs after peak surge elevation where the coarse-sediment profile indicates recovery and actual accretion
after the storm and the fine-sediment profile shows no sign of recovery and actual erosion after the storm.
In general, both A2 and B1 profiles experience a similar accretionary trend just prior to peak surge levels.




SUMMARY


A series of physical modelling experiments is in progress at the Coastal and Oceanographic
Engineering Laboratory at the University of Florida. The performed experiments aim at investigating
the interaction between the seawall and beach profile in the area adjacent to the seawall in both landward
and seaward directions. Six experiments have been completed to date. This report compares the
experimental results from two of the experiments, namely A2 and Bl. These two were performed under
identical storm surge and wave conditions. The only parameter which was varied between A2 and B1
was the sediment size. The coarse-sediment profile is A2 and the fine-sediment profile is Bl.
The results of the comparison between A2 and B1 can be summarized as follows:
1) A general seaward sediment transport trend was observed in both experiments.
2) Similar accretionary trends occurred in both experiments in front of the seawall ( between 0 and 0.5
meters) prior to peak storm surge elevation.
3) At peak storm surge elevation both experiments experienced erosion. However, this erosional trend
occurred about 36 minutes earlier in Bl than in A2.









4) After peak surge level the A2 model beach recovered leaving a higher sand level at the seawall toe
than before the model storm.
5) After peak surge level the B1 model beach did not recover and the sand level at the seawall toe was
lower than before the storm.
6) At the seawall toe, the maximum decrease in sand level from the initial level was 1.3 meters in
prototype units for the coarse-sediment profile (A2) and 1.5 meters in prototype units for the fine-
sediment profile (Bl).




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.









4) After peak surge level the A2 model beach recovered leaving a higher sand level at the seawall toe
than before the model storm.
5) After peak surge level the B1 model beach did not recover and the sand level at the seawall toe was
lower than before the storm.
6) At the seawall toe, the maximum decrease in sand level from the initial level was 1.3 meters in
prototype units for the coarse-sediment profile (A2) and 1.5 meters in prototype units for the fine-
sediment profile (Bl).




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.








Wave Tank Experiment: Series A2
storm surge #2


model time [minutes]


- storm surge -+- wave height, gage 1 ->- wave height, gage 2


Wave Tank Experiment: Series B1
storm surge #2


















I I C I I MC
100 150 200 250 300 350 400 450
model time [minutes]


- storm surge -+- wave height, gage 1 -?- wave height, gage 2


Figure 5. Measured wave height and storm surge conditions for (a) A2 and (b) B1.







Wave Tank Experiment: Series A2


0.1-
z

S 0-









a-0.
m -0.3-



-0.4-



-2 0 2 4 6 8 10 12 14
model distance from seawall toe [m)


-- 00 minutes elapsed -- 216 minutes elapsed --- 288 minutes elapsed


Wave Tank Experiment: Series B1
0.3


0.2-


> 0.1-





-0.4
0 -- --a^--------





0 -0.2-


-0.3-


-0.4-

-0.5
-2 0 2 4 610 12 14
model distance from seawall toe [m]


00 minutes elapsed 216 minutes elapsed ....- 288 minutes elapsed






Figure 6. Measured profiles at model times of 0, 216, 288 minutes for (a) A2 and (b) Bl.

13






Wave Tank Experiment: Series A2
range of profile fluctuation


model distance from seawall toe [m]


Wave Tank Experiment: Series B1
range of profile fluctuation


model distance from seawall toe [m]


Figure 7. Comparison of profile envelopes for (a) A2 and (b) B1.







Comparison Between Series A2 and B1
profiles after 216 minutes elapsed


model distance from seawall toe [m]


- series A2 series B1


Figure 8. Comparison of (a) A2 and BI profiles at 216 minutes elapsed time and (b) elevation differences
from initial profiles in the proximity of the seawall.









Comparison Between Series A2 and B1
profiles after 252 minutes elapsed


'4- _A

2-

0-

2-
A- --- T A-------- --^^


It I I I II I
-1 -0.5 0 0.5 1 1.5 2 2.5
model distance from seawall toe [m]


-- series A2 series B1


Figure 9. Comparison of (a) A2 and B1 profiles at 252 minutes elapsed time and (b) elevation differences

from initial profiles in the proximity of the seawall.









Comparison Between Series A2 and B1
profiles after 288 minutes elapsed


model distance from seawall toe [m]


- series A2 series B1


Figure 10. Comparison of (a) A2 and B1 profiles at 288 minutes elapsed time and (b) elevation

differences from initial profiles in the proximity of the seawall.


0
S0.0




'8
E r
C300





























sand-level fluctuations at seawall toe


C
S0.12-



I 0.1-
o.




L 0.08-



0.06-



0.04 ...i--.,---_,I---..I
0 50 100 150 200 250 300 350 400 450 5(
model time [minutes]


-0- series A2 -4-- series BD















Figure 11. Comparison of time history of sand level at the seawall toe for A2 and B1.


18











Physical Modelling Progress Report for:


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


Interim Report #2


UI


prepared by the
Coastal and Oceanographic Engineering Department
University of Florida
Gainesville, Florida


November 30, 1993


W









1. SCOPE OF THIS REPORT


This report summarizes the progress of wave tank experiments recently performed at the University
of Florida's Coastal and Oceanographic Engineering Laboratory facilities in Gainesville, Florida. These
experiments were performed with the objectives of comparing and evaluating seawall effects for the DNR
Coastal Construction Control Line study. Table 1 provides a summary of the wave tank experiments
completed to date, as well as those experiments that are planned in the near future. The various experimental
parameters listed in Table 1 are described in section two of this report. Fourteen separate experiments are
listed in Table 1. Of these, Series A and C have been completed. As well, the Series B experiments which
have been performed are B1, B2, and B6. Experiments B3, B4, and B5 of this series are projected to be
finished within the next three weeks.
Several comparisons can be made among the experiments so far completed. Series A2 and B1 were
compared in the first interim report emphasizing the effects of different sediment size on the profile response
in the model beach. This report will focus on the results of the Series C experiments. Specifically, the Series
C comparisons will address the extent of erosion occurring near the seawall resulting from two different wave
periods (1.65 versus 1.3 sec, model units) and two different wave types (i.e., random versus regular waves)
while the storm surge is held constant at its maximum predicted value, 0.144 meters (model). These
comparisons are presented in section three of this report. Future reports will deal with other comparisons
as interest dictates and time allows.




2. 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 con-
trolled 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 other end of the wave tank where
the model beach is located.










Table 1. Summary of experimental cases and test parameters.


water level characteristics seawall characteristics sediment wave characteristics water
initial stepwise varying const. straight, vertical median wave type deep water wave volume
Experiment profile storm surge level model elevation diameter regular random wind wave height period overtopping
Series model peak level ] [cm] [cm] [mm] waves waves waves [cm] [s] seawall
14.4 16.8 14.4 21.12 22.34 19.90 0.18 0.09 16.0 14.0 1.65 1.30 measured
#1 #1 #2 #3 #4 ##1 1 #2 #3 #1 #2 #1 #2 #3 #1 #2 #1 #2


Al X X X X X X X
A2 X X X X X X X
A3 X X X X X X X X
A4 X X X X X X X X X



B1 X X X X X X X
B2 X X X X X X X
B3 O O O O O O O O
B4 0 0 0 0 0 0 0 0
B5 O O O O O 00 0
B6 X X X X X X X X



C3 X X X X X X X X
C4 X X X X X X X X
C5 X X X X X X X X
C6 X X X X X X X X


0: not yet completed; X: completed



























"--J
ELEV.- (M --
















U-j
Q




















w >


In i s




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XU7
:|













t d
O n <
-- S"f5
\ 0
"~i u i









XI I I r
c ^ i_^
iu~ ~ V f E"
x \

=5w-









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 predeter-
mined 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 model time increments of 36 minutes corresponding to 180
minutes in the prototype.
Two capacitance type wave gages were installed in the tank for monitoring waves. Gage one is located
18.3 meters seaward of the seawall and gage 2 is located 5.3 meters seaward of the seawall.
The volume of water overtopping the seawall during some experiments is measured by collecting the
water in a movable catch pan located immediately landward of the seawall.


2.2 Scaling
A model to prototype length scale ratio of 1:25 and time scale ratio of 1:5 were 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. All dimensions in this report are given in model units unless
otherwise stated. The rest of the parameters listed in Table 1 will be explained in the following subsections.


23 Initial Profile and Seawall Configuration
The initial profile used in the 14 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. Figure 2 shows the initial profile for the model beach measured in Experiment C3.
There are three straight, vertical seawalls listed in Table 1. The first one, Seawall #1, is modelled
after the actual seawall located at R-192 which has an elevation of 5.28 meters (prototype). Seawall #2 is
identical to the first except for an elevation of 0.305 meters (prototype) higher than Seawall #1, whereas
Seawall #3 has an elevation 0.305 meters (prototype) lower than #1. Only Seawall #2 was studied in the
Series C experiments reported herein.













0.25

S0.20

Z 0.15

' 0.10

.2 0.05

S0.00
"3
1 -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 2. Model beach initial profile for C-Series experiments.







2.4 Storm Surge

The time-varying severe sea conditions to be physically modelled are listed in Table 1 as storm surges

#1, #2, #3 and #4. These severe sea conditions are numerically determined combined total storm tides

(Dean et al., 1992). These total storm tides include storm surges, astronomical tide, and dynamic wave set-up

which occurs 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). In contrast to the time-

varying water level of these aforementioned storm surges, Storm Surge #5 was held at a constant level of 0.144

meters (3.6 m prototype). This water level is the peak predicted value for the Highland Beach area in Palm

Beach County.



2.5 Sediment Size

Median diameters of the two sediments listed in Table 1 are 0.18mm 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. Sand #2 was used in all of the Series B and C

experiments.


--- .----------.---. seawall # 2
elevation 0.223m
C Series
initial profile





NOVD -

---- 0 minutes elapsed "--- --..-------










2.6 Wave Conditions

Both regular and random waves are modelled in the wave tank experiments of Series B and C. The
regular waves were modelled with a design 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 were

used in the regular wave experiments listed in Table 1. Wave Period #1 is 1.65 seconds in the model which
corresponds to a prototype value of 8.25 seconds and Wave Period #2 is 1.3 seconds in the model which

corresponds to 6.5 seconds in the prototype.

The random waves were modelled by a Pierson-Moskowitz spectrum with a significant wave height
of 0.16 meters (4.0 m prototype). For the random waves, two modal wave periods were modelled. These

correspond to wave periods #1 and #2 listed in Table 1. Figure 4 shows the spectral densities for the random
wave experiments C5 and C6 discussed in this report. The measurements were obtained from gage #1 located
18.3 meters (457.5 meters prototype) seaward of the seawall.




3. COMPARISON OF SERIES C EXPERIMENTS


Series C experiments can be considered as sensitivity studies which demonstrate the effect of different
wave periods and different wave types on the profile response of the model beach. All other experimental

parameters for these studies were the same (see Table 2). The fixed parameters are shaded in Table 2 and

include: Initial Profile #1, Storm Surge #5, Seawall #2, and Sand #2 of Table 1. The initialprofile is shown

in Figure 2. The storm surge is modelled as a constant water level at 0.144 meters above NGVD, the peak
calculated value. The seawall is a simple, straight vertical section with a model elevation of 0.223 meters
(5.585 meters prototype). The sediment is a very fine quartz sand with a median diameter of 0.09mm (0.21mm

prototype). The volume of water overtopping the seawall during each experiment was also measured.

Table 2. Experimental parameters for C-Series.

Experimental C3 C4 C5 C6
Parameter model prototype mode prototype model prototype model prototype

constant SWL [m] 0.144 3.600 0.144 3.60 0.144 3.600 0.144 3.600
wave type regular regular regular regular random random random random
wave period [s] 1.650 8.250 1.300 6.500 1.650 8.250 1300 6.500
sed. median diam. [mml 0.090 0.210 0.090 0.2J0 0.090 0.210 0.090 0.210
seawall height [m] 0.223 5.585 0.223 5.585 0.223 5.585 0.223 5.585












4.5

4.0

13.5
Z

I 3.0

. 2.5

22.0

2 1.5

.o 1.0

8
0.5

0.0


0 5 10 15 20 25 30 35 40
model time [x36 minutes]


Figure 3. Continuous prototype and stepwise model storm surges.


45 50


70


-o --- .........-- -.-.- --- ... experiment: C5 C6
.Hs [m]: 0.16 0.16
Tm [s]: 1.65 1.30


... ..... .. . .. . ....... ......... .. ... ...... . --------------- ---------- .--........ e x p e r t -
40 ----.-- ----.---- ---- .. .


3 -. ....... .... .


...0 -.-..--... .. ............
0 -- I












0.0 0.5 1.0 1.5 2.0
frequency [hertz]


Figure 4. Spectral densities for random wave experiments C5 and C6 measured at gage 1 (18.3m seaward of seawall).
'Si /





/ \ i-<-' i


0.0 0.5 1.0 1.5 2.0
frequency [hertz]



Figure 4. Spectral densities for random wave experiments C5 and C6 measured at gage 1 (18.3m seaward of seawall).










All four Series C experiments (C3, C4, C5 and C6) were run for a total of 108 minutes (9 hours
prototype). Profiles were measured at intervals of 36 minutes in the model (3 hours prototype). These
profiles are the solid lines shown in Figures 5 through 8. Also plotted in these figures as a dotted line are the
differences in profile elevation from the initial profile. These plots of the elevation differences facilitate
comparisons between experiments by removing any variations which may occur in the initial profiles of
different experiments. Several general observations can be made from these figures.
For all four experiments, a nodal point is observed at approximately 2 meters (50 meters prototype)
seaward of the seawall toe. A general erosional trend occurs between the seawall and this nodal point,
whereas, a general accretionary trend occurs seaward of this point for all experiments. Behind the seawall,
sediment volume is conserved for C3 and C4 (both regular waves). However, extreme erosion takes place
behind the seawall for experiments C5 and C6 (both random waves). The difference in profile response is
discussed further in the following subsections on the effect of different wave periods and different wave types.


3.1 Effect of Different Wave Period
The profile response from two different wave periods for regular waves is studied by comparing
experiments C3 (wave period 1.65 sec) and C4 (wave period 1.3 sec). Figure 9 shows the elevation differences
from the initial profile for the three time intervals measured. The solid lines in Figure 9 correspond to
experiment C3 and the dotted lines correspond to experiment C4. Similar profile responses are exhibited in
this figure.
For random waves, the profile response from two different wave modal periods is examined by
comparing experiments C5 (modal period 1.65 sec) and C6 (modal period 1.3 sec). The elevation differences
from the initial profile are plotted in Figure 10. In this figure, the solid and dotted lines correspond to
experiments C5 and C6, respectively. Similar to the observations for regular waves, the effect of different wave
periods on the profile response is small for random waves.


3.2 Effect of Different Wave Type
The profile response for different wave types for a wave period of 1.65 seconds (8.25 sec prototype)
is observed by comparing experiments C3 (regular waves) and C5 (random waves). Figure 11 shows the
elevation differences from the initial profile for the three time intervals measured. The solid lines in this
figure correspond to experiment C3 and the dotted lines correspond to experiment C5. A similar general
trend of erosion and accretion is exhibited in Figure 11 for both C3 and C5. Seaward of the seawall, the
points of maximum erosion and maximum accretion for C3 are shifted slightly landward of the similar points














Experiment C3

regular waves / wave period: 1.65s


0






0
"004).
40
0D
0
z"





0,







0.






S0o.
Zo.





-0.




-0.
0.
0








-0


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


2.5 3.0


3.5 4.0


0.25 -

z 0.20-

i 0.15 -

S0.10-

0.05-
0
> 0.00

--0.05 -

-0.10 -

-0.15


Figure 5. Model beach profiles and elevation differences from initial profile experiment C3.


.30

seawall # 2 36 minutes elapsed
.25 elevation 0.223m

.20

.15- _SWL
0.144m
.10

.05
NGVD
10 _________________ ______________________'- ~---__-______ ----




10o I -- 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
model distance from seawall toe [m]

.30
seawall # 2 72 minutes elapsed
.25 elevation 0.223m

.20

.15 SWL
0.144m
.10

.05
NGVD --
.00 -- -- ----------

05// \

.10 I 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
model distance from seawall toe [m]

seaa. #2 108 minutes-elapsed


seawall # 2
F elevation 0.223m


0.144m



---------- -------


NGVD


"--~


-- model beach profile ---- difference from initial
,I


1 108 minutes elapsed


L --- ----


-"'


~----------~













Experiment C4

regular waves / wave period: 1.30s


z






I
0)
0)
CO








0
CO



1
0)








a"
,0





z
0)
0)
CO

0


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


Figure 6. Model beach profile and differences from initial profile -- experiment C4.


0.30
seawall # 2 36 minutes elapsed
0.25 elevation 0.223m

0.20
SWL
0.15 -
0.144m
0.10-

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

-0.05

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

-0.15 ,,,
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.(
model distance from seawall toe [m]

0.30
seawall # 2 72 minutes elapsed
0.25 elevation 0.223m

0.20-
SWL
0.15 -
0.144m
0.10-


NGVD __, -- ..--- --
0.00 -

-0.05 I_/" __....

-o.1o model beach profile ---- difference from initial

.0.15 -. 1 1 1 1
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.1
model distance from seawall toe [m]

0.30-
seawall # 2 108 minutes elapsed
0.25 elevation 0.223m

0.20-
SWL
0.15 -
0.144m
0.10 -

0.05 N

0.00 -- -

-0.05 -

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

.-.15


z


o;



Q
0


Q
0)
CS



0
o
CO


2.5 3.0 3.5 4.0










2.6 Wave Conditions

Both regular and random waves are modelled in the wave tank experiments of Series B and C. The
regular waves were modelled with a design 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 were

used in the regular wave experiments listed in Table 1. Wave Period #1 is 1.65 seconds in the model which
corresponds to a prototype value of 8.25 seconds and Wave Period #2 is 1.3 seconds in the model which

corresponds to 6.5 seconds in the prototype.

The random waves were modelled by a Pierson-Moskowitz spectrum with a significant wave height
of 0.16 meters (4.0 m prototype). For the random waves, two modal wave periods were modelled. These

correspond to wave periods #1 and #2 listed in Table 1. Figure 4 shows the spectral densities for the random
wave experiments C5 and C6 discussed in this report. The measurements were obtained from gage #1 located
18.3 meters (457.5 meters prototype) seaward of the seawall.




3. COMPARISON OF SERIES C EXPERIMENTS


Series C experiments can be considered as sensitivity studies which demonstrate the effect of different
wave periods and different wave types on the profile response of the model beach. All other experimental

parameters for these studies were the same (see Table 2). The fixed parameters are shaded in Table 2 and

include: Initial Profile #1, Storm Surge #5, Seawall #2, and Sand #2 of Table 1. The initialprofile is shown

in Figure 2. The storm surge is modelled as a constant water level at 0.144 meters above NGVD, the peak
calculated value. The seawall is a simple, straight vertical section with a model elevation of 0.223 meters
(5.585 meters prototype). The sediment is a very fine quartz sand with a median diameter of 0.09mm (0.21mm

prototype). The volume of water overtopping the seawall during each experiment was also measured.

Table 2. Experimental parameters for C-Series.

Experimental C3 C4 C5 C6
Parameter model prototype mode prototype model prototype model prototype

constant SWL [m] 0.144 3.600 0.144 3.60 0.144 3.600 0.144 3.600
wave type regular regular regular regular random random random random
wave period [s] 1.650 8.250 1.300 6.500 1.650 8.250 1300 6.500
sed. median diam. [mml 0.090 0.210 0.090 0.2J0 0.090 0.210 0.090 0.210
seawall height [m] 0.223 5.585 0.223 5.585 0.223 5.585 0.223 5.585














Experiment C5

random waves / modal wave period: 1.65s


seawall # 2 36 minutes elapsed
s- elevation 0.223m


SWL
0.144m
3 -


NGVD




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

51
.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 toe [m]

s a # 2 72 minutes elapsed


0.35



0o.2
0.1




S0.05

>. 0.00
So.l


-0.1
-0.01




0.13


0.3
P 0.2

0.1

S0.1

a 0.1
2 0.0

0.0
>0.0
o)

S-0.0.





0.1.

0.35

S0.2(

0-.1








0.0



-0.1


2.5 3.0


3.5 4.0


5



o0



5

0

5
0

5

o




r



1


S


)


S


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


Figure 7. Model beach profile and differences from initial profile -- experiment C5.

11


-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.(
model distance from seawall toe [m]


seawall # 2 108 minutes elapsed
elevation 0.223m


SWL

0.144m



NGVD -

-I ---- ---


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


seawall # 2
elevation 0.223m


"1 0.144m




-- -- -- -- ---------- -


I/


S model beach profile ---- difference from initial


72 minutes elapsed |


"' ---


-





-0

-

-0


NGVD


--.,____________~~.-__-----_^__.-7-TL--,














Experiment C6

random waves / modal wave period: 1.30s


0.30-

0.25-

0.20-

S0.15 -

S0.10-

0.05
03


0.00--
o~oo ------------I ----_--- .-- --- --- - _E 5 -------_ ^ -

-0.05 ... ...... "

-d.10 model beach profile ---- difference from initial

-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 toe [m]

0.30-
seawall # 2 72 minutes elapsed
0.25 elevation 0.223m

0.20
----- SWL
0.15 -L
0.144m
0.10

0.05 -
N O V D ---. - -- - -
0.00
0 ---------------------- ---_- _-^---=
0.05 --~-__..

-0.io "-' -- model beach profile --- difference from initial

-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 toe [m]

0.30
seawall # 2 108 minutes elapsed
0.25 elevation 0.223m

0.20
-SWL
0.15 -L
S0.144m
0.10


NGVD .. '--... .-~.-----...
0.00- 1 ----------------------------

0.05 -0 '

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

-0.15 i,-, ,--


>
1)












0









z
0
0i
o-




0.
















0


0.5 1.0 1.5 2.0
model distance from seawall toe [m]


Figure 8. Model beach profile and differences from initial profile -- experiment C6.

12


seawall # 2 36 minutes elapsed


seawall # 2
elevation 0.223m


0.144m


NGVD


-1.0


1 36 minutes elapsed I


2.5 3.0 3.5















Comparison Between C3 and C4


regular waves / different wave periods


S- 36 minutes elapsed

0-

5 -

0-. seawall # 2

5 -





-- C3 (T=1.65s) -- C4 (T=1.30s)



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


S0.3(

0.2

0.2(


0.1
4a



0.1
0.0l


0.00
*0
-0.05
> -0.10







0.

0.2




0.1
0.1






0.0
S 0.2







S-0.1
C
4) 0.0

-9




> -0.1
4)3


1.0 1.5 2.0
model distance from seawall toe [m]


0.30

0.25
-ra
S0.20

0.15
0
0.10
o.io

0.05
I-
4o

S-0.05

> .0.10

.n 15


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


3.0 3.5 4.0


Figure 9. Elevation differences from the initial profile -- comparison between C3 and C4.


model distance from seawall toe [m]


0 -

5-

0-

5 -

0 -

5 -






1) -


108 minutes elapsed


seawall # 2


'2


S_ I--- C3(T=1.65s) --- C4(T=1.30s)

...,-


-

-

-

-


c----- ---~
c~














Comparison Between C5 and C6

random waves / different wave periods


-a



0







*,,a
I-
(U
Ca


a
CO
a











.
4)




U
C3



4)
I





:a
Ca





0
a
s
g
'5.
4)
4)


-1.0 -0.5 0.0


0.5 1.0 1.5 2.0
model distance from seawall toe [m]


2.5 3.0 3.5


0.30 -

0.25 108 minutes elapsed









-o------------ --
. 0.20
0.15






-0
modl do. seawall #2

S0.05 -.

0.00- --- --- -


- .--o __ -- C5 (Tm=1.65s) --- C6(Tm=1.30s) |


-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 toe [m]


Figure 10. Elevation differences from the initial profile -- comparison between C5 and C6.


0.30

0.25 36 minutes elapsed

0.20 -

0.15 -

O.o1 seawall # 2

0.05 -

0.0)

-0.05 -^--.^--
| -- C5 (Tm=1.65s) C6 (Tm=1.30s)
-0.10
-0.15 ,---- i ---- ,--------,-i ----- i ----- ] ,-------,------ l, ---
-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 toe [m]

0.30

0.25 72 minutes elapsed

0.20 -

0.15

0.lo seawall # 2

0.05 -

O.CO-


F-- C5(Tm=1.65s) ---- C6(Tm=1.30s)
-0.10

-0.15














Comparison Between C3 and C5

wave period = 1.65s / different wave types


0
'4









.2

0















.4-









4)
0

CO
a
E


















4)
a



'S










I-











o
u
.43




T



a
0
CO




4)
4i

















0
4)5
0
CO
45





.4-
CO
0
CO
4)


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


Figure 11. Elevation differences from the initial profile -- comparison between C3 and C5.


0.30

o.zs 36 minutes elapsed

0.20a -

0.15 -

o.io seawall # 2

0.05 -

o.10- 1 ------

-0.05
-.- C3 (regular waves) ---- CS (random waves)
-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
model distance from seawall toe [m]


0.30

0.25 72 minutes elapsed

0.20 -

0.15

o.o seawall # 2

0.05

0.005 -_ ---.

-0.05 -
-- C3 (regular waves) --- C5 (random waves)
-0.10

40.15
-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 toe [m]

030

.25 108 minutes elapsed

0.20 -

0.15 -

0.1 seawall # 2

0.05 -
0.00 -- '-



-- |--- C 3 (regular waves) --- C5 (random waves)
-0.10

4-0.15 ,,,,


2.5 3.0 3.5 4.0










for C5. There is only a slight difference in the magnitude of these points with C3 being greater in both
maximum erosion and maximum accretion. Landward of the seawall, the location of the point of maximum
erosion is similar for both C3 and C5. However, the magnitude is markedly different with C5 exhibiting much
more erosion.
The profile response from regular and random waves for a wave period of 1.3 seconds (6.5 sec
prototype) is observed by comparing experiments C4 (regular waves) and C6 (random waves). Figure 12 shows
the elevation differences from the initial profile for these experiments. Similar to the trend observed in Figure
11 seaward of the seawall, the points of maximum erosion and accretion for the regular waves are shifted
slightly landward of the similar points for the random waves. As well, landward of the seawall, erosion is
significantly greater in the case of random waves as opposed to regular waves.




4. SUMMARY


A series of physical modelling experiments is in progress at the Coastal and Oceanographic
Engineering Laboratory at the University of Florida. The purpose of these experiments is to investigate the
interaction between the seawall and beach profile in the area immediately adjacent to the seawall. Eleven
experiments have been completed to date. This report, the second in a series, compares the experimental
results for all the Series C experiments. These experiments include C3, C4, C5, and C6. The objective of
these comparisons is to investigate the effect of different wave periods and different wave types on profile
response.
The effects of two different wave periods are examined by comparing the results between C3 (wave
period 1.65 sec) and C4 (wave period 1.3 sec), both regular wave experiments. Also, this effect is examined
in the comparison between C5 (modal period 1.65 sec) and C6 (modal period 1.3 sec), both random wave
experiments. Profile response to regular versus random waves with similar wave periods is examined by
comparing C3 (regular waves) and C5 (random waves). This effect of different wave types on profile response
is also examined in comparisons between C4 (regular waves) and C6 (random waves). All four Series C
experiments were performed under fixed storm surge and seawall conditions.
The results of the comparisons described above are summarized as follows:
1) The effect of using two different wave periods, 1.65 and 1.3 seconds, for the case of regular waves as
observed in C3 and C4 is relatively insignificant.















Comparison Between C4 and C6


wave period = 1.30s / different wave types


0.25

0.20

0.15

0
o



0.0
I-




4- o.0o


. -0.10
Q)








-0.10





.41



S0.1

.0.10
S.0.15























0.20




0.0
a 0.15











0.
I I
- o.io


4)



-01
-0.05
Ca









S0.30

0.0(

.> 0.2




4a

g 0.0.
I-


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



5 -

0 -



- seawall# 2



5 -




-- -- C4 (regular wave
0- \ ----

s --- i ------------- i -----


Figure 12. Elevation differences from the initial profile -- comparison between C4 and C6.


36 minutes elapsed


seawall # 2


__________-


C4 (regular waves) --- C6 (random waves)




-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.(
model distance from seawall toe [m]




72 minutes elapsed






seawall # 2




-

-- -
~... |- -- C4 (regular waves) --- C6 (random waves)


-4


-

-

-

-


2.5 3.0 3.5 4.0










2) The effect of using two different modal wave periods, 1.65 and 1.3 seconds, for the case of random waves
as observed in C5 and C6 is also relatively insignificant.
3) The effect of using regular versus random waves as observed in comparing C3 and C5 (for a wave period
of 1.65 seconds) and in comparing C4 and C6 (for a wave period of 1.3 seconds) is extremely significant
landwvard of the seawall. To a lesser extent there are also differences observed seaward of the seawall.
Landward of the seawall, the random waves induced greater magnitudes of erosion, whereas seaward of the
seawall the regular waves induced greater amounts of erosion. These observations immediately adjacent to
the seawall are clearly represented in Figure 13.




5. REFERENCES


Coastal and Oceanographic Engineering Department, University of Florida, 1993. Evaluation study and
comparison of erosion models and effects of seawalls for the Coastal Construction Control Line.
Physical Modelling Progress Report -- Interim Report #1. University of Florida, Gainesville, Florida,
18pp.
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.










for C5. There is only a slight difference in the magnitude of these points with C3 being greater in both
maximum erosion and maximum accretion. Landward of the seawall, the location of the point of maximum
erosion is similar for both C3 and C5. However, the magnitude is markedly different with C5 exhibiting much
more erosion.
The profile response from regular and random waves for a wave period of 1.3 seconds (6.5 sec
prototype) is observed by comparing experiments C4 (regular waves) and C6 (random waves). Figure 12 shows
the elevation differences from the initial profile for these experiments. Similar to the trend observed in Figure
11 seaward of the seawall, the points of maximum erosion and accretion for the regular waves are shifted
slightly landward of the similar points for the random waves. As well, landward of the seawall, erosion is
significantly greater in the case of random waves as opposed to regular waves.




4. SUMMARY


A series of physical modelling experiments is in progress at the Coastal and Oceanographic
Engineering Laboratory at the University of Florida. The purpose of these experiments is to investigate the
interaction between the seawall and beach profile in the area immediately adjacent to the seawall. Eleven
experiments have been completed to date. This report, the second in a series, compares the experimental
results for all the Series C experiments. These experiments include C3, C4, C5, and C6. The objective of
these comparisons is to investigate the effect of different wave periods and different wave types on profile
response.
The effects of two different wave periods are examined by comparing the results between C3 (wave
period 1.65 sec) and C4 (wave period 1.3 sec), both regular wave experiments. Also, this effect is examined
in the comparison between C5 (modal period 1.65 sec) and C6 (modal period 1.3 sec), both random wave
experiments. Profile response to regular versus random waves with similar wave periods is examined by
comparing C3 (regular waves) and C5 (random waves). This effect of different wave types on profile response
is also examined in comparisons between C4 (regular waves) and C6 (random waves). All four Series C
experiments were performed under fixed storm surge and seawall conditions.
The results of the comparisons described above are summarized as follows:
1) The effect of using two different wave periods, 1.65 and 1.3 seconds, for the case of regular waves as
observed in C3 and C4 is relatively insignificant.










2) The effect of using two different modal wave periods, 1.65 and 1.3 seconds, for the case of random waves
as observed in C5 and C6 is also relatively insignificant.
3) The effect of using regular versus random waves as observed in comparing C3 and C5 (for a wave period
of 1.65 seconds) and in comparing C4 and C6 (for a wave period of 1.3 seconds) is extremely significant
landwvard of the seawall. To a lesser extent there are also differences observed seaward of the seawall.
Landward of the seawall, the random waves induced greater magnitudes of erosion, whereas seaward of the
seawall the regular waves induced greater amounts of erosion. These observations immediately adjacent to
the seawall are clearly represented in Figure 13.




5. REFERENCES


Coastal and Oceanographic Engineering Department, University of Florida, 1993. Evaluation study and
comparison of erosion models and effects of seawalls for the Coastal Construction Control Line.
Physical Modelling Progress Report -- Interim Report #1. University of Florida, Gainesville, Florida,
18pp.
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.













(A) sand-level fluctuations at seawall back


N- '




-1








0 1 2 3 4 5 6 7 8 9
model time [x36 minutes]


(B) sand-level fluctuations at seawall toe


1 2 3 4 5 6 7 8 9
model time [x36 minutes]


-E- C3:regular waves,T= 1.65s -o- C4:regular waves,T= 1.30s
--- C5:random waves,Tm= 1.65s --- C6:random waves,Tm= 1.30s


0.24


S0.22


" 0.2


S0.18


0.16


* 0.14

0.12


0.12


0.1


0.08


0.06


0.04


0.02


Figure 13. Sand-level fluctuations at (A) seawall back and (B) seawall toe.

19


3




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