Design and performance of headland bays in Chesapeake Bay, USA

The use of headland-breakwater systems along the shore of Chesapeake Bay began in the early 1980s. Properly designed and installed headland breakwaters with beach fill and wetlands plantings provide shore protection and create a “full” coastal profile of beach/backshore/dune which enhances habitat. They create a tertiary buffer for upland runoff and groundwater and provide access and recreation. The wetland grasses also create an erosion resistant turf. The coastal profile accommodates environmental permitting requirements of habitat enhancement for shore protection structures.The Static Equilibrium Bay (SEB) model of Hsu and Sylvester has shown its utility in defining the pocket or embayed beach planform between headland breakwaters. Bay plots for varying wind/wave conditions and water levels define the limits of shoreline change. The embayed beach must be high and wide enough to offer protection, usually for the base of a graded upland bank, under design storm conditions. The embayed beach morphology should emulate nature; the existing beach profile should be assessed first in designing any headland-breakwater system. The design of the beach begins with establishing the minimum design beach width (Bm) and profile in the context of stable embayed beaches held by headland breakwaters. With Bm established, breakwater length (Lb), the breakwater gap (Gb) and the bay indentation distance (Mb) come into play depending on the wave environment. The empirically derived relationships between these parameters are offered as a guide for breakwater design along the sheltered coasts of Chesapeake Bay.Constructing stable headland/embayed beaches for long-term shore protection can be done cost effectively. The procedures developed over the years to evaluate and design headland breakwaters have been, in retrospect, effective. These installations provide a database of successful headland-breakwater installations, some of which are over 20 years old. This database will continue to be used to verify and compare parameters for headland systems in the future as sites continue to mature.