EM 1110-2-1100 (Part V)
31 Jul 2003
(3) Ecosystem restoration. A new area of concern is the restoration of lost environmental resources such
as wetlands, reefs, nesting areas, etc. In 1990, the U.S. Army Corps of Engineers was directed to also
consider ecosystem restoration where a Federal project has contributed to ecosystem degradation. For this
chapter, Corps civil works project objectives and special design constraints (economic, environmental,
institutional, etc.) have been omitted. They have all been brought together in Part V-8. Where appropriate,
differences between the Corps' design approach and a general design approach are discussed here.
b. Alternatives for shore protection.
(1) Overview. Figure V-3-2 (adapted from Gilbert and Vellinga 1990) schematically displays five
alternative ways to mitigate the damage of coastal storms, namely, accommodation, protection, beach
nourishment, retreat and of course, the do-nothing alternative. Civilization's artifacts at the coast are here
represented by the lighthouse at a fixed reference line. Storm surge and storm erosion reduce the distance
between the reference line and the sea. Sea level rise and historic, coastal erosion also reduce the distance,
but at slower time scales. Beach nourishment accomplishes the same objective as the retreat option (i.e.,
increase the distance to the sea).
(a) Pope (1997) has a similar classification system summarized in Table V-3-1.
Table V-3-1 Classes of Management and Engineering Response for Shore Protection (Pope 1997)
Draw the line
Slow down the erosion rate
Fill up the beach
Live with it
(b) The protection category in Figure V-3-2 is divided into armoring (seawalls, bulkheads, etc.) for
flooding and moderation (groins, breakwaters, etc.) for erosion mitigation and shoreline stabilization. Beach
nourishment or restoration is sometimes called the soft alternative to the armored or hard alternative for shore
protection. Figure V-3-3 displays the shift from hard to soft, beach nourishment projects over the past 50
years by the Corps of Engineers (from Hillyer 1996).
(c) For design, consider the following six types of alternatives, namely: armoring, beach stabilization
(moderation) structures, beach nourishment, adaptation and retreat, combinations (and new technologies) and
the with-no-project (abstention) alternative. Table V-3-2 summarizes these alternatives for coastal hazard
mitigation including the sections where full discussions are presented.
(2) Armoring. Seawalls, bulkheads, and protective revetments for cliffs and dikes are the traditional
types of armored shorelines. The cost of armoring is justified when flooding and wave damage in low areas
threaten substantial human investment. On historic, eroding coasts, it must be expected that erosion will
continue to diminish the width of the buffer strip between armored shoreline and the sea. If a recreational
beach is present, periodic beach nourishment must be anticipated. Part V-3-2 gives functional design details
Shore Protection Projects