The breaking wave height must be specified. An estimate such 
as one inferable from WIS is adequate for this purpose. 
1a 
e. The time history of the storm surge in 0.5-hr increments must 
be specified. 
140. Dune and berm elevations in increments of 0.5 ft were specified 
in the original model. Material eroded from the dune and berm (or deposited 
on the berm) is assumed to erode equally from each elevation contour. The 
internal empirical parameters (such as k in Equation 7 and Q, in Equa- 
tion 10) have been shown to produce acceptable results without alteration. 
The above physical descriptors of the storm event and the areas to be modeled 
represent all of the data required for the numerical simulation of the inter- 
action processes. 
141. To simulate the presence of the seawall in the project area, 
the Kriebel model was modified by replacing the dune area (shown in Fig- 
ure 21) with a vertical wall. Material deposited offshore is equally sup- 
plied by each berm contour line until recession reaches the seawall. At this 
point recession ceases and the beach in front of the seawall begins to rapidly 
erode. Since the model cannot describe the scour process at a wall, the cal- 
culation is terminated when the seawall becomes exposed at MSL. Further ero- 
sion might result in undermining of the structure. Figure 23 conceptually 
illustrates shoreline erosion and recession for cases with and without 
seawalls. 
142. Following the completion of modifications to the Kriebel model, 
testing was performed to verify that the resultant model was capable of simu- 
lating the erosion patterns and volumes which were documented to have resulted 
from an actual storm event. This verification precess is described in the 
following section. 
Model Calibration and Verification 
143. A quantitative assessment of the predictive capability of the 
Kriebel model was reported by Birkemeier et al. (1987). Although the range 
of parameters (storm surge level and duration, and dimensions of the dune and 
berm) was limited by the available data, comparisons of model output to pre- 
and post-storm survey data were made for 14 separate profiles representing 
four different East Coast storm events. Table 7 presents a summary of 
a 
