Explanation of flooding

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Explanation of the flooding of the River Derwent.

By Clive Brewer

 

I grew up with an understanding of the River Derwent system in the Vale of Pickering, given to me by my father and grandfather, who both worked with the rivers.  The Ordnance Survey map of Malton and Pickering, and that of the North Yorkshire Moors Eastern Area, are both helpful in understanding the siting and flowing of the rivers.

 

I was born in 1939 in the village of Normanby in the centre of the Vale of Pickering, alongside the River Seven. This was eight years after the ‘great flood’ of 1931.  My grandfather on my mothes side had lost his harvest in the 1931 flood, and, at a later date, his sheep, which were poisoned by the ‘green slime’ left on the land.  This almost put the family into bankruptcy, a fact of which my late mother never ceased to remind me.

 

My grandfather on my father’s side was a land drainer when the old-style clay tiles were dug into the ground by hand.  In the 1930s he was made foreman by the then newly-formed River Ouse Catchment Board.  My father then followed his father in this occupation.  He in turn was promoted to foreman when his father retired.

 

He did this throughout the war years, and afterwards became the general foreman of the River Rye Internal Drainage Board until about 1949.  These jobs were considered so important that, during the war years, they were classed as reserved occupations.  I have learned much of this matter from my father and grandfather, and at such a time as this I want to share it with others who are equally concerned for the future.

 

The Vale of Pickering in ancient times was a lake. In time it drained itself through the area which is now Old and New Malton, and Norton, then into the Vale of York through Kirkham Gorge.  The Vale of Pickering remained swampy, with the main river systems of the Rye and Derwent carrying the water.  This explains why the villages are on the edges of the Vale, apart from those on hilltops, such as Little Barugh, Great Barugh and Edstone.

 

The drainage of the area was poor until the major drainage scheme of the 1930s onwards was carried out by the River Ouse Catchment Board.  The work involved deepening the channel and moving the river banks, which were previously adjacent to the river, so that they became further away.  This created a flood plain above the towns of Malton and Norton for the river in times of excess water.  The operation began around Kirkham Weir below Malton.  It progressed up the River Derwent to the area of Yedingham, and up the River Rye (which rises in Bilsdale), and its main tributaries, being Pickering Beck, the Seven (which rises in Rosedale), the Dove which rises in Farndale, and the Holbeck which rises in the area of Ampleforth/Coxwold.  This work was carried out on the lowest parts of the Vale which were subject to flooding, in order to prevent the flooding of upstream villages and homesteads which had occurred in the past; and to ensure that the massive amount of water from all these rivers was able to flow through Malton and Norton without causing flood damage.  Most importantly, it enabled the rivers to empty in a natural sequence.

 

The river Seven normally reaches its peak flow, then recedes, approximately six hours after rainfall in the area ceases.  This is followed by peaking in the Rye (between half a day and two days later, depending on rainfall), then peaking in the Derwent (which occurs at Malton approximately three days after the peaking in the Seven).  Should these main river channels be allowed to become wholly or partly blocked by vegetation or silt, then this natural flow sequence cannot take place.  This results in a build-up of water which prevents the next river in sequence from emptying naturally, and creates a progressively worsening situation along the river system.  When extra water from high rainfall and/or thawing snow on the high moors, mainly at the head of the River Rye, reaches this build-up of water, a flood is the natural result.

 

Sir George Cayley (1773-1857), engineer and local land owner, had the foresight to build a canal to drain the eastern watershed of the Derwent from Hackness to the sea via Scalby Beck, thus preventing flooding to the land below Forge Valley at West Ayton.  Very little of this water now flows though Malton and Norton, as can be seen by the size of the Rye at Howe Bridge and the Derwent at Yedingham.  The meeting of these rivers, approximately three-quarters of a mile south-east of Howe Bridge, cannot be seen in times of flood, due to the massive amount of water.  But it can be seen clearly when not in flood, although the difference is less obvious since recent work has widened the Derwent at this point.  The Derwent is the only outlet for the water from all these river systems.  This water will continue to flow downhill whenever it rains or when snow thaws excessively – this is the basic principle of the drainage system.

 

The drainage system worked efficiently until recently, when vegetation and silt have been allowed to block the channels.  In my opinion, the floods will continue to occur progressively more often, and in times of less rainfall, unless the original drainage plan is re-adopted by all the relevant authorities. We should also take heed that the flood of 1931 happened during harvest time.

 

Blocking the river system above Howe Bridge will only result in the flooding of the upstream villages of Brawby, Normanby, Marton and Salton, as used to occur in the 1930s. It will not prevent the flooding of Malton and Norton, as water will continue to arrive above this point, eventually breaking through with greater force.  This could then cause structural damage downstream where the River Derwent is concentrated under the Malton by-pass. It would them emerge into Old Malton and the towns, before continuing on its natural journey, as it has always done, down to Kirkham Abbey (which did not flood this time) and through the gorge.

 

The work which my father and grandfather carried out was on emergency relief channels, and these should be maintained as such.  The engineers of those days designed this work without the aid of modern computer technology, using only common sense and practical observation of the water levels and behaviour.  We should not neglect their wisdom and foresight.  Liquid always flows to the lowest point, or as Grandfather said, ‘Watter allus runs doonhill

 

Clive Brewer

1999 & 2007

This refers to the floods of March 1999

 

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