We all know what can happen when you get a bucket load of rainfall in a short space of time. Our 19th century approaches to civil engineering (Which we seem to cling to) and increased urbanization mean we have huge areas covered with impermeable surfaces. Combine this with the more intense periods of rainfall, which we expect to get worse, through climate change lead to vast quantities of water running off surfaces which our rivers, streams, surface drains and sewers struggle to deal with. Most of North East England escaped the type of destruction seen in the South, but a quick trip sampling trip the day after storm Angus shows the serious volume of water that accumulated in the Seaton Sluice catchment.
While the destructive force of this water is clear, what is often overlooked is the drop in water quality that accompanies storm events. The pictures below show the contrast in turbidity, in summer (Left) the water is pretty clear, but the storm water (Right) is horridly turbid. This is caused by fine sediments, ripped from the river bed, banks and surrounding fields by the force of the water. The results are usually a massive amount of erosion to river banks, the sediments can also cause issues when they are deposited downstream and fill in reservoirs and river basins.
But sediments are not the only thing carried on-mass by the storm water. E.coli concentrations after storm Angus were up to 100 times higher than in the water just the week before (below).
Where do they come from? The E.coli have a range of sources, most come from the faeces of mammals, this could be from sheep and cow faeces, slurry or manure when the water washes over fields or from humans when sewers overflow. It can also be from the stream bed where E.coli from faeces have been deposited when the stream flow is low. Why does it matter? With E.coli comes pathogens, bacteria and viruses that cause health problems for humans.
The issue isn’t that we have a lot of water, it is that we have a lot of water that we can’t deal with very well. The answer, I believe, doesn’t lie in building bigger and bigger flood defenses. Whilst they do offer protection and can be worthwhile investments, they are a short term solutions, 19th century engineering applied to 21st century problems. The idea that we can just build bigger to overcome our problems has stuck with us since Victorian times. Better solutions lie in holding water up higher in the catchment, reducing the area of cities which is impermeable and reducing the rate at which storm water enters sewer systems. Not only does this deal with the quantity of water, many of the solutions actually improve the quality of the water as well. There are some fantastic projects out there showcasing more sustainable options for dealing with storm water, my favorite is Philadelphia Water. They have a great mixture of engineering and community involvement covering a whole city and their green solutions are having fantastic benefits beyond simply managing the quantity and quality of storm water.