While news headlines this past week highlighted flood and
devastation on the Mississippi in the US, Europe has been
agonising about the long-term drought in the Mediterranean (see
Focus, this issue). Both catastrophes have their own timescales,
and both inflict devastating human misery. In an effort to tame
great rivers, many have inadvertently been made worse. For two
centuries, engineers have raised the Mississippi's levees ever
higher to keep it from inundating its natural flood plain. But,
with more than $7 billion spent in the past 60 years, the work
has been largely self-defeating. The Mississippi's swamps and
flood plains, from Iowa to Louisiana, were once natural
reservoirs, receiving water from rivers when they flood and
evening out the seasonal variation in flow. Raise the levees and
the flow in the river becomes greater during floods, bringing
new threats downstream. Meanwhile, with no water stored on the
flood plains, the ... To continue reading this article,
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