Recommended procedure for computing erosion layer thickness and selecting a design cap erosion thickness

Recommended procedure for computing erosion layer

thickness and selecting a design cap erosion thickness

This section describes a recommended procedure for computing the ero-

sion layer thickness for open-water capping sites. Also provided is a dis-

cussion on how the erosion thicknesses can be used to select the design

erosion thickness for the cap.

One of the primary outputs of a frequency of erosion study will be a se-

ries of curves similar to the one shown in Figure 28. This figure shows

the return period frequency of a given amount of vertical erosion for a

year of extratropical storms acting on a mound in the Mud Dump site with

a base depth of 73 ft and an 8-ft-high mound for a crest depth of 65 ft.

The solid curve is the mean erosion predicted based on 100 simulations;

error bars define plus or minus one standard deviation. Values from the

curve can be translated into a tabular form. For northeast coast sites that

experience both tropical and extratropical storms, the values from both

types of storm are combined into a single return frequency table, such as

the one as shown in Table 6 generated for the Mud Dump site.

Figure 28.

Frequency of vertical erosion from extratropical storms acting on a mound in Mud Dump

site with a base depth of 73 ft and an 8-ft-high mound for a crest depth 65 ft

Chapter 8 Long-Term Cap Stability