r
urban conditions, in order that these elements may function with a
reasonable degree of naturalness, remain compatible with one another and
with human purposes, and be available for people's enjoyment. Flood
plains make good hay fields or parks, for instance, but poor sites for
homes or shopping centers. Porous areas that recharge aquifers ought to
be kept as much as possible under vegetation rather than pavements or
buildings, if people are to have streams later and not capricious drains
that are better off covered over. Steep slopes, if carved severely,
usually exact a later revenge. House clusters and townhouses and
apartments rightly spaced and located can let the country function even
while settling on it numbers of people equivalent to those who would be
there if it were hacked into a solid expanse of tiny lots. And so on.

Much remains to be learned if the application of these principles is to
be ideal. For example, urban hydrology--precisely what happens to the
water cycle during various kinds of development, and how it might be
adjusted--is a relatively new branch of study and still needs much
research. But even with present knowledge, great improvement over
present patterns is possible. In the hands of a few emerging experts,
planning which pays attention to soils and topography and climate and
special landscape features and values can be a subtle art, prescribing
villages and farms and factories in the right places, making the most of
native vegetation and views and places where George Washington slept and
the breezes of July. Its form on a map tends toward curved lines rather
than the orderly straight ones abhorred by nature.

Yet in one simple form, this kind of land use planning has been
practiced for many years in rural America by millions of farmers, who
have cooperated with one another to their own mutual benefit in soil
conservation programs to reduce erosion and to slow down the wasteful
and destructive runoff of precipitation. We noted earlier a pilot urban
adaptation of such programs on Pohick Creek on the metropolitan fringe
in Virginia, where an effort is being made to develop a whole stream
basin in accord with soil conservation principles, not only to avoid
future flood damages and sedimentation and pollution but to retain
natural areas, living streams, and many of the other features the land
had before the city engulfed it. Even with the gaps in present knowledge
and the probability that dev