Geography Reference
In-Depth Information
defenses generally work, they occasionally fail in the face of record high water, as
happened spectacularly and tragically in the cases of the Mississippi and Missouri Rivers
during the summer of 1993. Indeed, critics claim that, for two reasons, these bulwarks
merely guarantee that the inevitable flood will be exceptionally and unnecessarily disas-
trous. First, they say, the human earthworks (levees) create a false sense of security that
encourages construction and settlement in patently hazardous areas. Second, artificially
high levees negate the natural “sponge effect” of long, wide floodplains, and therefore
magnify the effects of the inevitable flood.
Low-cost federal flood insurance is an interesting variable in relation to the floodplain. It
clearly and compassionately helps to relieve the pain and suffering of people who “lose
everything” in times of flooding. But critics claim its promise of compensating individual
losses also encourages settlement of hazardous areas, and thus may serve to increase
the very suffering it seeks to relieve.
Waves and currents
Coastal areas bordering oceans and seas witness significant gradational activity. Every wave that
strikes land potentially performs mechanical weathering, however minutely. Every drop of wave wa-
ter that soaks land may contribute to chemical weathering. And, of course, every wave and coastal
current, if strong enough, can erode sand and other coastal particles and deposit them somewhere
else. As a result, coastal zones are among those parts of Earth that are most prone to change by natur-
al means.
Eroding cliffs
Cliffs characterize many coasts, and are a sure sign of erosion. Each wave mi-nutely helps to weather
and erode the base of those landforms, undermining the entire cliff. Eventually, a portion of the cliff
collapses and the shoreline
retreats,
that is, erodes inland. Figure 7-5 shows an example of a cliff
formation. The rate of erosion varies from one cliff to the next depending on its composition. For ex-
ample, a cliff composed of a mix of soil, gravel, and rock retreats far more rapidly than one composed
of solid rock.
“Million-dollar views” may be had from cliffs, and that often results in prized pieces of property.
The fact that a cliff is an erosional feature, however, virtually guarantees loss of adjacent real estate.
Property owners who build houses close to drop-offs sometimes try to artificially stabilize the cliff to
prevent further erosion. While such efforts usually are effective against minor storms, they stand little
chance against repeated major ones.
