CU Mar-Apr 2020

COMMENT
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Comment
Water, water everywhere...
by David Chadwick
February saw the wettest month on
record - much of it, it seems, dumped
on the hills feeding into the River
Severn, with the consequent floods
drowning communities along its length. The
catastrophes that persistent rainfall has
produced this year, though, have affected
many other areas both in the UK and
overseas, including Australia, after months
of forest fires, South America and some US
States. Whether attributed to global
warming or other factors, the frequency and
intensity of such storms appears to be
increasing, and they likely to get worse.
The anguish of those caught in the floods
is heart-rending, and we can only concur
with the emotional plea that the flood
defences put in place are not adequate, and
that we must throw more money at the
problem. The problem is 'how much', 'where'
and 'how we should use it'?
Putative solutions are being proposed by
many bodies from, the UK Government to
developers, explaining how their adherence
to current flood mitigation requirements
allow them to contemplate building new
houses on flood plains.
The biggest question of all, though, is the
first one - how much will it cost to protect all
of those communities that are being hit time
and time again, both now and in the future,
when the problem is projected to get much
worse? The answer, I am afraid, is that the
amount will be staggeringly large, and that
any plans to protect one community have to
be linked in with plans to protect the next
one downstream, which will be swamped by
flood waters hitting them faster and fuller.
The money required to protect every
community will surpass what can be
achieved by emotional or social appeals,
and will need to be submitted to cold
financial fact. Decisions about what can,
should, or cannot be protected will need to
be backed by considerations of the costs
involved. If you want to protect towns like
Shrewsbury, which is flooded regularly by
the River Severn, then you may have to
sacrifice some of the adjoining land.
I have nothing against Shrewsbury and use
this merely as an example to illustrate the
situation we are rapidly finding ourselves in,
and to highlight the article in this issue by
Robert Mankowski, VP, Digital Cities of
Bentley Systems, who argues that we have
the resources to quantify the effects of
extreme weather events, and thus make the
necessary financial decisions to support
flood defence schemes, or to discard them
as hopelessly extravagant. Keep in mind
that the cost of rebuilding the levees after
Hurricane Katrina in New Orleans has been
estimated at $20 billion.
It's another example of the benefits of
creating a digital twin of a town, city or even
country, which brings together all of the
various quantifiable elements of any given
area, and allows analyses and assumptions
to be made about it, including, as you will
see, its hydrological status and the cost of
installing flood relief schemes.
London is perhaps in a more precarious
situation than Shrewsbury. It already suffers
from isostatic rebound - an ongoing natural
occurrence since the shrinking of the Ice
Age ice caps which is causing the UK
tectonic plate to tilt, sinking in the South and
rising in the North. This is exacerbated by
water extraction and bad planning over the
last couple of hundred years, and now by
rising sea levels caused by global warming.
How soon before the Thames starts cresting
the embankment?
The floods knocked Brexit off the front page
- and now since first writing this comment
COVID19 has overtaken everything. It’s far
too early to make assumptions about the
future of infrastructure and the construction
industry - or indeed anything else - as the
state of the pandemic is still too fluid. We will
no doubt have much more to discuss in
future issues.
4 March/April 2020