EM 1110-2-1100 (Part V)
31 Jul 2003
Shore Protection Projects
The main purpose of this chapter is to summarize alternatives and their functional design for shore protection.
Coastal defense and stabilization works are used to retain or rebuild natural systems (cliffs, dunes, wetlands,
and beaches) or to protect man's artifacts (buildings, infrastructure, etc.) landward of the shoreline. A
secondary purpose is to review the many constraints that will influence the final design.
a. Major concerns for shore protection
(1) Storm damage reduction. Coastal storms generally cause damage by two mechanisms.
(a) Coastal floodings. On the Atlantic Ocean and Gulf of Mexico coasts, tropical storms (hurricanes)
produce elevated water levels, (storm surge) that inundate and damage coastal property. Extra tropical storms
(northeasters) along the eastern seaboard and other coasts also create high water and flood damage. Damage
from coastal flooding is arguably greater than that due to high winds on the world's coasts.
Following the devastating flood in 1953, the Dutch people began the Delta Project to raise the dikes
and construct barriers (dams) across the estuarine openings to the North Sea. The last component
was the Oosterschelde (Eastern Scheldt) storm surge barrier as displayed in an aerial view in
Figure V-3-1a and a photograph of the movable gates in Figure V-3-1b. It is one of the largest
coastal engineering projects ever completed in the world and a major engineering achievement.
Inland flooding also disrupts traffic, business, medical services, and normal life to produce
secondary, economic and social impacts.
(b) Wave damage. Elevated water levels also bring higher wave energy inland to damage upland
development. Damage is a nonlinear function of wave height. On the West Coast, the elevated ocean surface
of El Nino events coupled with high storm waves causes damage to marinas, piers, and coastal infrastructure.
(2) Coastal erosion mitigation. The second major concern is coastal erosion. Storms create short-term
erosional events. Natural recovery after the storm and seasonal fluctuations may not be in balance to produce
long-term erosion. Shore protection projects moderate the long-term average erosion rate of shoreline change
from natural or manmade causes. Reduced erosion means a wider sediment buffer zone between the land and
the sea. And consequently, erosion mitigation translates into storm damage reduction from flooding and wave
attack. How natural shorelines remain stable and mitigate upland damage is explicitly reviewed in Part V-3-
3-a. Use of the terms flood control and erosion control are discouraged. Complete control of coastal flooding
and erosion is a myth that gives a false sense of security to the client, the general public, and the media. Man
cannot control nature. There is always the chance for a more powerful storm than the level of shore
protection provided within the design constraints. A reduction in potential levels of flooding and erosion,
i.e., mitigation means storm damage reduction benefits and the need for a risk-based, design philosophy, as
Shore Protection Projects