Freshwater and marine coast ecology 97Spivey 2002, Formanet al.2003,Jared2004,Frazer 2005).Peak f low,the max-
imum height reached, is the primary determinant of flood damage. Riparian
vegetation, plus vegetation depressions and other stormwater detention basins,
are primary solutions for reducing peak flows. These solutions also permit more
watertosoak into the ground so streams do not dry out as readily in dry seasons.
Stream corridors (blue-green ribbons) are often prominent in urban regions.
Marine coasts
The abundance of cities on or near a coast means that extensive areas
of coastline are within urban regions and subject to the manifold effects of
concentrated people. Coastal areas themselves are as complex as the built areas,
so identifying and addressing the key problems is not simple (Beatleyet al.1994,
Smith1996,Breen and Rigby 1996). Nevertheless, it is clear that coastal areas
are especially rich in biodiversity. The combination of freshwater, brackish, and
saltwater habitats, the highly heterogeneous coastline produced by gradual land-
surface variations relative to water surface, the dynamic nature of the zone
affected by daily winds, waves, and water flows, plus extreme weather events,
provides countless microhabitats for rare species and natural communities. Also
coastlines are used by many migratory fish, turtles, and birds that move out to
sea, up rivers, across the land, and along coastlines.
Four major terrestrial coastline types are easily recognized.Rockycoastlines
experience high wave energy, have a rather distinct elevational zonation of
plants and animals, and often an abundance of tidepools full of rather unusual
species. Second,sandy coastlines,including barrier islands, under natural condi-
tions commonly have dunes, grass-covered areas, woody vegetation, lots of feed-
ing shorebirds, sometimes nesting sea turtles, and high wave energy. But beaches
are magnets for urban people, who largely eliminate the dunes, grass, woody
cover, shorebirds, and nesting turtles. Linear hard structures such as jetties and
walls are often built and rebuilt and rebuilt again after periodic big storms, and
significantly alter, not only the beach area, but also the marine area (Pilkey and
Dixon1996). Barrier beach islands, river deltas, lower floodplains of rivers, and
other sandy areas near cities often experiencesaltwater intrusion,where seawa-
ter movesinland a distance, under surface freshwater. This results either from
excessive pumping out of freshwater, or the upslope diversion of freshwater that
would normally recharge the groundwater. Saltwater intrusion causes wells to
produce undrinkable water.
The third major coastline type,coastal wetlands,includes marshes (grassy),
mangrove swamps in the tropics, and mudflats at the mouth of rivers. These wet-
lands have gradual elevational changes and gradual salinity changes from fresh-
water tobrackishtosaltwater.Also, daily, monthly, and storm tides repeatedly