Rainfall Problems Harvest time

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Rainfall problems and flooding would be exacerbated by the proposed Eco town at Elsenham and Henham

26th July 2008 - by Jonathan Leech

It is a recognised fact that when you pave over an area of ground, the rain that would have previously soaked into the ground runs off as it needs to go somewhere. This means pipes, ditches and rivers to dump the water into the sea before it can be cleansed by passing through the earth to give us fresh drinking water in the future.

The Government has already recognised this problem with off road parking as more people convert their front gardens into parking areas. So let us assume the proposed Eco town is based on a 1 mile square area, although by the time the shops, factories, parking and housing are built, it will probably finish up resembling Harlow which is say 9 square miles.
 
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So 1 square mile of proposed land for an Eco town (probably more)

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1 mile = 1760 yards or 1604 metres

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So 1604 X 1604 metres = 2,572,816 square metres of land

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Take 25 mm rain (1-inch)

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To fill a box 1 meter cube, divide 1000-mm by 25-mm = 40

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So every 40 square metres of land receiving 25-mm of rain would fill our box.

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Now we have 2,572,816 square metres of land, so divide this by 40 = 64,320 boxfuls of rain water to dispose of with just 25-mm rain

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Put end to end in a pipe 1 metre square and we get a pipe 64.32 kilometres long.

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Put a flow rate of 5 kilometres per hour and it takes almost 13 hours to empty.

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Make that 4 inches of rain and it becomes a disaster.

 
The water shed, or start of the river Cam is at the highest point in Henham at Spring gate farm, also being the start of the River Stort. From here the Cam runs down to North Hall Road at the corner of the turn to Little Henham where it is joined by a tributary that starts somewhere close by the railway station. The stream that is never dry then continues on to Newport and Audley End before meandering its way to Cambridge.

Old Mead Road - Aug 2001

 

Old Mead Road - Aug 2001

Flooding in the valley used to be much worse especially at locations like Toot Toot Bridge which was, for want of a better word a ford. The river used to run to a point about 50 meters before the bridge where there used to be a very small pipe that ran under the road and through the bridge, the road being single track at that time past the wood yard. You could rest your bike on the rail and watch the water disappearing down the pipe just inches below your feet.
 
So it only took a splash of rain to flood the road which is why they dug out the river and tunnelled under the railway to put in a larger pipe. This pipe started with an iron grate at both ends to stop people getting in, but it was soon discovered that branches and debris blocked the entrance and exits and were removed when the flooding got worse.
 
The River Cam and the tributary from Elsenham station take all the water from the valley head which starts roughly along the ridge formed by the Thaxted road.

So I imagine all the rain from Station road and Elsenham itself run towards the station which is where the first floods occur by the railway car park.

From here the fields on both sides of the valley drain down towards Old Mead Road and North Hall Road which forms a very large area. Considerable development in recent times has added to the problem as more and more of Elsenham is paved over, however one of the biggest problems in recent years has been the M11 motorway as this represents a huge paved area of many square miles. All this rain water is drained into the Cam at various places adjacent to Old Mead Road and North Hall Road from Elsenham and extends along as far as Newport. There being several large pipes at places like the Ugley turn off North Hall Road, Widdington turn just before the B1383, and on the south side of Newport that take rain water from the M11 to the Cam. Newport is already designated a flood risk area and the playing fields act as the flood plain, often over 1 metre deep, and you have all seen the lawns at Audley End House when the river is in full flow.

Similar problems also exist on Hall Road if you drive from the Crown Pub towards Mole Hill Green, but I donít know the history of this area other than the flood area just as you leave Elsenham.

Moving on to Stansted Lower street at the bottom of Grove Hill, as a child I remember this being flooded every year, and even now with all the work to clear the River Stort it still floods from time to time. This is of course the River Stort on this side of the valley, but it still wreaks havoc from time to time.

Jonathan Leech

Resident of Henham for 30 years and born in Stansted in 1947

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