Settings and forms of urban regions 285populations moving from stream to stream may be sustained, a goal especially
attainable in the upriver portion.
The sliced-donut form provides insight into key locations for numerous other
characteristics of importance to natural systems and their uses by society --
groundwater to provide clean water supply, flood hazard areas, riverside recre-
ation sites, where riparian vegetation can have the greatest benefit, areas to
protect aquatic ecosystems, and the best and worst areas for urbanization. The
following sliced-donut types represent variations on the basic model, each with
readily estimated implications for people and nature:
Large river bisecting city (and metropolitan area). Bangkok, Brisbane
(Australia), Paris, Cairo, Columbus (USA), Delhi, Edmonton,
Novosibirsk (Russia), Bamako, Rome, Warsaw
City located at intersection of large rivers.Lyon(France), Minneapolis/St. Paul
(USA), St. Louis (USA), Portland, Seville (Spain)
City overwhelmingly on one side of a river.Quebec, Vienna, Memphis (USA)
City in a major valley between high ridges.Caracas, Bogota, Zaragoza (Spain),
Guatemala City, Kayseri (Turkey), Grenoble (France)
City on a delta.St. Petersburg, Karachi, New Orleans (USA), Rangoon
(Myanmar/Burma), Rotterdam (Netherlands), Cairo, Cuttack,
Lagos, Vancouver (Canada), Calcutta, ShanghaiCoastal cities
Flattening one side of a donut to represent a coastline makes the donut
model work well for coastal cities. Theflattened-donutform varies in the degree
of flattening and thus length of coastline. An extreme flattening creates a semi-
circular metro area and region, such as Barcelona or Toronto. The city is located
on the coastline subject to, e.g., hurricanes/cyclones, tsunamis, and under-
ground saltwater intrusion, but also with the glories of a seaside or lakeshore
location. More moderate donut-flattenings represent conditions where the city
is set back from the coast, somewhat protected from the big problems just
mentioned.
Asecond geometric component of the flattened donut is to add the central
river slice or line so that it is perpendicular to the coastline. Most coastal cities
originated where a river met the sea or a large lake. A third key spatial compo-
nent, an indentation or nibbled-out area at the intersection of the lines, mimics
thetypical coastal bay or natural harbor present where a river meets the sea.
In short, theflattened-sliced-indented donutmodel represents most coastal urban
regions.