the Middle Ages,
and as winter storms return, the spectre of floods is returning
too. Just weeks ago, the river Rhone in south-
east France burst its banks,
driving 15,000 people from their homes, and worse could be on the way.
Traditionally, river engineers have gone for Plan A: get rid of the water fast, draining it off the land and
down to the sea in tall-sided rivers re-engineered as high-performance drains. But however big they dug city
drains, however wide and straight they made the rivers, and however high they built the banks, the floods
kept coming back to taunt them, from the Mississippi to the Danube. Arid when the floods came, they
seemed to be worse than ever. No wonder engineers are turning to Plan B: sap the water’s destructive
strength by dispersing it into fields, forgotten lakes, flood plains and aquifers.
B. Back in the days when rivers took a more tortuous path to the sea, flood waters
lost impetus and
volume while meandering across flood plains and idling
through wetlands and inland deltas. But today the
water tends to have an
unimpeded journey to the sea. And this means that when it rains in the
uplands, the
water comes down all at once. Worse, whenever we close off more
flood plains, the river’s flow farther
downstream becomes more violent and
uncontrollable. Dykes are only as good as their weakest link and the
water
will unerringly find it. By trying to turn the complex hydrology of rivers into the
simple mechanics of
a water pipe, engineers have often created danger where
they promised safety, and intensified the floods
they meant to end. Take the
Rhine, Europe’s most engineered river. For two centuries, German engineers
