Thursday 7 January 2016

Dam Nation

I have returned to a full week of work after the Christmas and New Year break.

I was a bit nervous on the first day back, not from having to make friends again with all of my colleagues, that they might notice my few extra pounds from over indulgence or that I was sporting at least three new bits of clothing from Santa but because my diary included appointments out of the office in the areas recently badly affected by the flooding caused by record persistent rainfall  since early December.

I did think that I might be prevented from getting to the North Yorkshire towns of Selby, York, Malton and Pickering by road closures or other traffic problems and had kept up to date through local radio and national news bulletins.

Yes, I did see extensive areas of town and countryside under deep, murky water in all of these locations causing considerable misery and chaos from ingress damage. There were diversions around submerged roads.

There was however one remarkable exception.

Pickering, that picturesque market town on the edge of the North Yorkshire Moors and Dalby Forest was its normal, functioning self.



Granted, the Beck which runs straight through the middle of the town was a bit swollen but importantly it was easily within its course and existing defences, whereas in the other regional towns similar measures had been completely overwhelmed or rendered ineffective.

This was not down to any micro-climate influences, a freakish rain shadow area (December 2015 rainfall on the town was three times the average for the month) or luck but through good lateral thinking and planning in a fully co-operative and cohesive way by a group of local stakeholders including the Forestry Commission and landowners, under the theme of "Slowing the Flow"

The facts are clear to appreciate.

Flooding appears to be and is perceived by the public as being an increasingly common event and one that could get even worse with climate change. Pickering has a long history of flooding and whilst a flood alleviation scheme has been proposed in recent years, it is of too low a priority in terms of cost-benefit to be considered for approval. The town is particularly at risk from summer flash floods due to the steep nature of the catchment.

Pickering has been flooded four times in the last 10 years  (1999, 2000, 2002 and 2007), with the last flood the most serious to date, causing damage to homes and businesses valued at approximately £7m. The impact of the 2007 floods was particularly severe across the whole of the Yorkshire and the Humber Region, with the total damage estimated at £2.1 billion.

"Slowing the Flow" at Pickering seeks to demonstrate how better land management can help to tackle the flooding problem faced by Pickering in North Yorkshire, in common with many other towns and cities across the country.

Measures implemented have not cost the earth or imposed unreasonably on the livelihoods and outgoings of individuals.

One major contributing factor has been the use of large woody debris dams help to increase flood storage by creating an upstream pool and reconnecting streams with their floodplain.



                               A typical large woody debris dam in a semi-natural woodland stream

Large woody debris (LWD) dams are a common feature in natural woodland streams but have been actively removed from most river systems in the UK due to concerns that they reduce fish movement and can be washed downstream, blocking bridges and culverts.



However, these risks are increasingly thought to be outweighed by the ability of the dams to increase flood storage by raising water levels and reconnecting streams with their floodplain. The risk of washout can be reduced by limiting their formation to smaller watercourses (<5 m wide).

A total of 129 LWD dams have been installed within the Pickering Beck catchment and a further 38 in the adjacent River Seven catchment.



The Pickering Beck catchment in North Yorkshire is an ideal, although challenging site to explore how land management practices within an environmentally sensitive area can be modified for flood risk reduction.

Not all towns and cities in the UK may fit the Pickering model but some of the principles and practices may well be the means in the future by which to reduce or mitigate flooding risk.

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