Memorandum submitted by Michael A K Bell
(FL 149)
This letter is in reply to the letter I wrote
to Mr Michael Jack MP with regard to flooding on rivers in the
south west of England and North Yorkshire and he has told me to
put forward my ideas to you.
The cost of flooding already incurred and possible
in the future would, I think, make my idea feasible. If we accept
that rivers over thousands of years have silted up at various
points along their journeys to the sea and, by flooding, eventually
found a new route past the silted up point. This silting up has
rapidly increased with mans' activities including agriculture
and, accepting the fact that to dredge rivers is unacceptable,
due to the fact that under low flow conditions the surrounding
lands would have a much lower water table.
So we need a scheme which lowers the water level
in the rivers at a time when heavy rain fall occurs in this flood
plain or in the catchment area up stream of the flood plains.
To dredge rivers is a disaster for river life and my scheme would
limit the effects of this work over the period of the scheme.
My idea would be to create an artificial flood
plain or compensation reservoir upstream of the flooding, (no
this isn't a dam). We would build a moveable barrier across the
river, which would, in effect, be an adjustable (for height) weir.
The weir would be sited at a point in the river with a flat plain
on each side for, say, approximately one mile and then a rise
in ground level to minimum height of, say, 7 metres, this rise
in ground feature along with an earth wall extending out from
the weir. Choosing the right site will allow us to enclose this
flood plain and allow possible back-up of the river level. This
weir, under normal conditions, would disappear into the river
bed and allow normal transition of wildlife up and down the river.
By monitoring the river level upstream (torrential
rain in the hills) we can immediately raise the weir and control
the amount of water rushing down to natural flood plain. If we
have torrential rain down stream of the weir (in the natural flood
plain) we can monitor the rising river level and immediately raise
the weir to compensate and allow the river to absorb more flood
water from the populated areas.
Ah! Ah! You're going to say but what does he
do with all this water building up behind the weir if we can't
allow it back down the river. By controlling the river level downstream
we allow the river to absorb more floodwater actually coming into
the river from run-off from roads, from buildings and from farmland.
We now have the problem from sustained raising
of the weir, by raising the weir and controlling river levels
downstream we have a build-up of water in our compensation reservoir,
the second part of this scheme now takes place. When the build-up
of water exceeds, say, this seven metres in our artificial flood
plain I would now connect a pipeline from the weir to the low
tide mark in the river estuary.
This sounds expensive but I would look at the
possibility of using recovered high grade plastic to make lined
pipes, say, seven metres in diameter and sinking a section at
a time into a trench in the centre of the river bed, savings in
length and improvements in gradients of the pipeline could be
made if bends in the river could be cut short. This involves disturbance
in the river bed but I wouldn't think that laying sections of
pipe at a time would involve more sediments than the river in
full flood.
Perhaps the pipelines from the two weirs in
the Avon and one on the Severn could be linked at their confluence
to continue down to the sea. Perhaps at the outlet of each weir
pipeline we could have another pipeline linking each weir and
continuing towards London for a water extraction scheme.
In summary, siting of the position of each weir
is critical in that we include small rivers, streams etc. upstream
of the weir as we can but still maintain as much height above
sea level as we can. We have gains at every stage of the schemes,
we can use the earth from the pipeline trench to build the earth
wall out from the weir to high ground features, the earth walls
could be grazed by farm animals and used to move away from the
rising waters when the weir is in a raised condition.
The first gain is reached when the weir and
earth walls are constructed and we have limited time for some
control of the river level. The second gain comes when the pipeline
gets past the areas of flooding and, or when, the pipeline passed
any areas of silting up of the river bed, at this stage by opening
the valve gates in the pipeline we can speed up the water flow
to the end of the pipeline wherever this has reached. When water
levels recede in the compensation reservoir the fields can return
to normal. Careful monitoring of the river level allows for:
1. Controls heavy upstream flows down to
the floodplain.
2. Compensates for runoff into the river
downstream of the weir (and flooding of populated areas) by control
of river levels downstream of the weir.
3. Under normal conditions allows for migration
of wildlife in the river.
4. A water extraction scheme for the southeast?
In additions to flooding on Avon/Severn Rivers,
recent bad flooding occurred in the Malton (North Yorkshire) areas,
due mainly to water flowing off the North York's moors. Could
this weir and artificial flood plain be employed in the river
Rye which carries enough water which we could control to make
a big difference to the flood problems in Malton/Norton? Dependent
on elevation and topography can we position a weir somewhere north
of Butterwick and run a pipeline west to the river Swale and create
a flood area on the river Swale.
This suggestion may seem strange, putting more
control water into (eventually the river Ouse) Swale and the problems
in York. With this flood plain on the Swale we now have the opportunity
to kill two birds with one stone in that we control water downstream
into the Ouse and we continue the pipeline down the Swale into
the Ouse and past York. Eventually the pipeline reaches the river
Humber and the excellent water quality could allow us to include
this in a water extraction scheme.
At some time in the future when we find a cheap
way of generating power we could insert pumps downstream of the
weir to assist flow in the pipelines and transport water as part
of a water extraction scheme.
I suggest savings could be made in some unnecessary
work initiated to try and alleviate the flooding we have at present.
Funding could come from a myriad of sources/Europe, insurance
companies, agriculture and water companies. If we carry out the
work over, say, 20 years the benefits for our children could be
huge.
Thank you for taking the time to read my suggestions.
Michael A K Bell
October 2007
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