D. Shoreline Stabilization Management Measure

Where shoreline erosion is a nonpoint source pollution problem, shorelines should be stabilized. Vegetative methods are strongly preferred unless structural methods are more cost effective, considering the severity of wave and wind erosion, offshore bathymetry, and the potential adverse impact on other shorelines and offshore areas.

1. Applicability

This management measure is intended to be applied by States to new and expanding marinas where site changes may result in shoreline erosion. Under the Coastal Zone Act Reauthorization Amendments of 1990, States are subject to a number of requirements as they develop coastal nonpoint source programs in conformity with this measure and will have some flexibility in doing so. The application of management measures by States is described more fully in Coastal Nonpoint Pollution Control Program: Program Development and Approval Guidance, published jointly by the U.S. Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce.

2. Description

The establishment of vegetation as a primary means of shore protection has shown the greatest success in low-wave-energy areas where underlying soil types provide the stability required for plants and where conditions are amenable to the sustaining of plant growth. Under suitable conditions, an important advantage of vegetation is its relatively low initial cost. The effectiveness of vegetation for shore stabilization varies with the amount of wave reduction provided by the physiography and offshore bathymetry of the site or with the degree of wave attenuation provided by structural devices. Identification of the cause of the erosion problem is essential for selecting the appropriate technique to remedy the problem. Methods for determining the potential effectiveness of stabilizing a site with indigenous vegetation are presented in Chapter 7.

Some structural methods to stabilize shorelines and navigation channels are bulkheads, jetties, and breakwaters. They are designed to dissipate incoming wave energy. While structures can provide shoreline protection, unintended consequences may include accelerated scouring in front of the structure, as well as increased erosion of unprotected downstream shorelines.

Among structural techniques, gabions, riprap, and sloping revetments dissipate incoming wave energy more effectively and result in less scouring. Bulkheads are appropriate in some circumstances, but where alternatives are appropriate they should be used first. Costs and design considerations of these and other structural methods for controlling shoreline erosion are presented in Chapter 6.

3. Management Measure Selection

Selection of this measure was based on the demonstrated effectiveness of vegetation and structural methods to mitigate shoreline erosion and the resulting turbidity and shoaling (see Chapters 6 and 7). Also, it is in the best interest of marina operators to minimize shoreline erosion because erosion may increase sedimentation and the frequency of dredging in the marina basin and channel(s).

4. Practices

As discussed more fully at the beginning of this chapter and in Chapter 1, the following practices are described for illustrative purposes only. State programs need not require implementation of these practices. However, as a practical matter, EPA anticipates that the management measure set forth above generally will be implemented by applying one or more management practices appropriate to the source, location, and climate. The practices set forth below have been found by EPA to be representative of the types of practices that can be applied successfully to achieve the management measure described above.

Detailed information on practices and the cost and effectiveness of structural and vegetative practices can be found in Chapters 6 and, respectively.