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<br />Coastal Development
<br />In coastal areas development has similar effects hecause
<br />the delicate halance of shoreline elements is easily upset
<br />The removal of heach sand and the leveling of dunes,
<br />along with the construction of seawalls, jetties, and piers,
<br />have been common practices in coastal construction. Yet,
<br />these measures weaken the shoreline's natural protection
<br />system hy introducing static elements into the dynamic
<br />process that, left alone, is able to respond to constant
<br />wind and wave action. Such changes exacerbate the im-
<br />pacts of storm surges and high winds. Filling natural Wet-
<br />lands to increase developable land also eliminates such
<br />natural defenses against flooding.
<br />
<br />Urbanization
<br />The effects of development on flooding are most pro-
<br />nounced in the urhan environment. If a building and its
<br />accessories, such as sidewalks, parking lots, and access
<br />roads, can increase water runoff, then the combined effect
<br />of many buildings, streets, parking lots, and sidewalks can
<br />increase it far beyond the capacity of the watershed sys-
<br />tem. The same is true of ocean-side cities and their effect
<br />on delicate coastal ecosystems.
<br />With the rapid expansion of cities since the late
<br />1940's, ever-larger concentrations of land have heen cov-
<br />ered with buildings and pavement. As a result, surface
<br />drainage has heen continually increased, and the capacity
<br />of the natural system to accommodate it has been ex-
<br />ceeded repeatedly And, the problem has not really been
<br />alleviated by flood control projects. On the contrary, flood
<br />control structures have encouraged much of the expan-
<br />sion onto floodplains, since these seemingly attractive
<br />building sites were thought to he protected
<br />Energy restrictions, economic forces, land specula-
<br />tion, increa."ies in household formation, and the desire for
<br />amenities will bring continuing pressure for urban ex-
<br />pansion As this development occurs, people both in and
<br />out of the huilding process must be aware of the full
<br />costs and other effects arising from the necessary inter-
<br />dependence of natural and social systems.
<br />
<br />Effects of Development
<br />The dangers of development in floodplains take several
<br />forms. As discussed above, development can increase the
<br />severity of flooding Also apparent is that huildings them-
<br />selves, subject to the forces of flood waters, will he dam-
<br />aged. And, when damaged, parts of a building can break
<br />loose and act as battering rams when carried by the cur-
<br />rent of the stream or storm surge.
<br />A less obvious danger can result from development
<br />in areas that are not suhject to direct flood hazard. Vir-
<br />tually every site is part of a riverine watershed or coastal
<br />
<br />
<br />-..... .....____'AI Before
<br />....
<br />........-
<br />--
<br />
<br />........
<br />,8 ........
<br />After ..........
<br />'" --
<br />
<br />---
<br />
<br />Construction of seawalls
<br />alters the dynamic halance
<br />of the co{L,tal ecosystem
<br />and causes erosion of the
<br />heach and seahed. The dot-
<br />ted line (A) represents the
<br />original profile with gently
<br />sloping heach and seahed.
<br />The profile afier construc-
<br />tion of the seawall (B)
<br />shows loss of heach area
<br />and steep slope of seabed.
<br />
<br />Groin.~., constructed to
<br />stahilize the heach at one
<br />point, can have a reverse
<br />effect for adjacent areas.
<br />Shoreline erosion increases
<br />the beach area updrift of
<br />the groin (A), hut de-
<br />creases it down-
<br />drift of the
<br />groin (B).
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