Whole regions
NewOrleans. Disaster-preparedness planning is important, but tends to become
high-profile following rather than before a disaster.
Flooding,following heavy rainfall and/or snowmelt, is the most widespread
disaster hazard in urban regions. The process is accentuated by hard surface
cover of buildings and associated roads that have spread on mountain- and hill-
slopes. Linear roads and their stormwater pipes accelerate stormwater runoff
to streams and rivers. But streams are commonly straightened, squeezed by
legal and illegal structures in floodplains, and channeled to underground pipes
with hydraulic rather than hydrologic water flows, further accelerating down-
water flows.Pipes and streams lead to rivers, which commonly have normal low
waterflowsand may seem inconspicuous or inconsequential. Yet rivers in urban
regions are commonly straightened, channelized with rock or concrete barri-
ers, squeezed from the sides, and pockmarked with bridges and other pilings.
Wetland sponges and floodplain riparian woodland are largely long-gone. The
combined result of these mountain/hillslope, stream, and river activities is peri-
odic big floods -- enormous water volumes zooming down a river channel, aimed
directly at the metropolitan area. Flood disasters result. A package of solutions
is the answer (Chapter 10 ;Forman 2004a).
Waterinurban regions
Important results and patterns relative to whole regions are grouped
as follows: (1) urban-region rings relative to metropolitan areas; (2) land cover
near and far from metro areas; (3) unique features near metro-area borders;
(4) border length of built area in urban regions; and (5) nearby major cities and
political/administrative units.
Urban-region rings relative to metropolitan areas
[R1]The metropolitan area is almost always a small, centrally located portion
of the urban region, averaging 8 % of the area, and being <1 % in a third of the regions
(Figure7. 14).
The rather large area beyond the metropolitan area, the urban-region ring,
means that typically a reasonable amount of space exists for multiple resources
and human activities in an urban region. Also resources are generally conve-
nient for the city, as the central nucleus of a region. However for two exceptions,
Chicago and Philadelphia, the metro area exceeds 25 % of the urban region, sug-
gesting that the urban-region ring and its resources are somewhat limited (Color
Figures 13 and27). Philadelphia is especially problematic because its region is
hemmed in by urban regions of surrounding cities. Indeed, a competition for