Sorry, this is too long, but I feel better for it!
As a 'wet' ecologist I’ve a lot of experience in water level management / flood risk and I’m always interested to see what people think about it. Rivers are dynamic i.e. they change over time depending on the flow. This naturally regulates how big the river is and what wildlife lives in it. In general, the system works well if left to its own devices. However, we’ve been fiddling with rivers and their catchments in a big way, especially since the industrial revolution. Rivers have always flooded and we’ve known this for centuries. However, we build extensively in the flood plain and then increase the catchment run-off speed by putting in underfield drains, gripping the moors, covering large areas in concrete / tarmac, ploughing fields perpendicular to the rivers, vastly increasing the sediment loads of rivers, filling them with silt, putting up bridges and culverts that reduce how quickly water can drain away etc. All this makes them more prone to flooding. Then we try and constrain all this extra water and silt by putting in higher flood banks. This just makes it worse for people downstream who have to put up with more water. Another favourite is over dredging the river so it looks nice and big. The problem being is that the river was the right size for its flow before it was dredged – if you over dredge a river it will just naturally fill itself in very quickly. This just kills the wildlife, starts a perpetual management problem which cost thousands to continue and gets people complaining that the river is full of silt and needs clearing ‘like they always used to do’.
We’re in a bit of a pickle because we have 63(ish) million people on a small island, we want places to live, transport systems, agricultural systems etc. and we don’t want any of it to be disrupted even for a few days by the physical / natural processes which by their nature have extremes i.e. everything needs to be constrained to fit exactly with our requirements. Unfortunately we’ve engineered a system to service our communities, which makes flooding worse and cannot be constrained due to the cost or damage it would do. The Thames catchment alone has more than 5500km of main river and much more ordinary watercourses and a 13000km2 catchment – we don’t have the resources to manage every river, field and urban area in an extreme event. What’s worse is the expected 20% increase in winter rainfall during this century.
What have we done about it? Well, quite a lot really.
a) We’ve recognised that floods can’t be stopped only managed to do least damage. That’s why the Environment Agency and Councils don’t do ‘flood defence’ any more they do ‘flood risk management’
b) Every catchment in England and Wales (I don’t know about elsewhere) now has a Catchment Flood Risk Management Plan (done by the Environment Agency). This looks at where flooding is most likely to occur and the best way to limit it e.g. use of flood plains in agricultural areas, by-pass channels, more flood banks, flood storage areas etc.
c) Hundreds of millions are being spent on implementing these plans. More money will implement it faster, as ever it’s down to political priorities.
d) Planners aren’t supposed to allow new developments in areas most at risk from flooding.
Other improvements are needed including, i) recognising that much of the urban flooding we see is due to inadequate urban drainage systems and not due to rivers, ii) people who live in flood plain need to be told this
before they buy a house iii) if any new housing must be on a flood plain it must be designed to make recovering from flooding far easier i.e. living areas above any predicted flood levels, iv) people need to understand that flood risk is generally measured as the risk over a 100 year period but that 1 in a 100 year event might happen tomorrow or in 199 years time – saying “I’ve been here 20 years and it’s never flooded so things must be getting worse” just shows that they don’t understand flood risk and not that things have necessarily got worse and v) just to make it topical, yes paving your front garden does increase flood risk for others – I’ve had to do this but I used gravel with deep soakaways which has increased infiltration through the clay under my house.
PS eeyore, Oxford is at quite a high flood risk even with the water meadows and a flood risk assessment is looking at how to reduce the risk. Have a look at this if you're interested
http://www.environment-agency.gov.uk...r_1113456.pdf?
Cheers,
Chris
I had to remove the fairing i couldn't peddle at all and so tied it to the rear rack even then cycling was still up against the belting winds. Come Snow -it's snow problem at all
the bike starts first time too on those cold frosty mornings great fun!!
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