There has been a lot of academic
content in this blog, so I’d like to take the opportunity here to write a post
that is more based on my own opinion. Just before Christmas last year the BBC
published an article talking about the Los Angeles River. The LA River is a huge artificial concrete
river channel that is designed to stop LA from flooding during high flows by
moving water away from the city quickly, and discharging it into the Pacific
Ocean. The arguments to return parts of the river to a more natural setting,
but these have been countered by hydrological worries, suggesting that changes in
rainfall extremes forced by climate change could cause large scale flooding of
LA.
I should make it clear from the
outset that I am not a fan of brutal hard engineering strategies to control
river systems. They are a relic of an unfortunate period of history where many
rivers were managed by over-zealous engineers with buckets of concrete in hands
and calculators in their pockets. It is unsurprising to see that the voices
singing the praises of the LA River in this article are from the Nasa's Jet
Propulsion Laboratory, lording over ‘the particular design, the angle, the
slickness of concrete’. The flood prevention characteristics of the channel are
important - but this brutalist design is certainly not the only method of
preventing flooding, and does nothing to address the large water shortages in
LA, a city that is piping in water from as a far away as the Colorado River
(which is drying up)! It will cost money, but some naturalisation of the
channel has to occur to restore LA’s parched aquifers, even if this just
involves diverting some water from the channel. This would also help reduce
flood risk, as there will be less water in the channel. Unfortunately this is a
difficult proposition; LA is now so built up around the river, some displacement
of people would have to occur.
I am not saying there is an easy solution,
because there isn’t. The main problem here is that we need to learn from past
mistakes – building huge concrete channels is a naïve and short term approach
to river management. Because there is so much new river run-off from increased
urbanisation there is no guarantee the current concrete channel would be
able to withstand rainfall totals similar to the LA flood of 1938 (the flood
that lead to building of the channel). Brutalist hard engineering strategies
like these are almost always doomed to fail – there is always an upper limit on
capacity, even if you think you are building something to be future proof. Add to this that once you have built up a city
next to a concrete channel that you have little room to expand if you reach
capacity, and you can see how silly the hard engineering fetishism of the
1940s-1970s was. Thankfully we now realise that a mixture of hard and soft
engineering strategies are the best way to manage rivers in the face of
changing future discharge, but it is very hard to undo mistakes like the LA
River.
I hope a suitable resolution to
the problem is found, but I fear Nasa will win and things will just stay as
they are, one day doomed to fail. At least we have to chance to act if we act
now.
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