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Geology and hydrogeology ... …

Report No. SRL/FP/004.1 (10/05/2006)

Page 2-6 Restoration levels for lakes H/I are presented in Figure 5.

Figure 5 of the ES shows a series of contours that are unrealistic and are

unrelated to the previous landscape. so above those on the track running

The contour lines are about 60 cm or from the level crossing at the western

end of the depicted disused railway track. On the track one a restored contour of 52.10m and also 51.46 next to a 52.20m. But the track shown is an old field-track. It would highest ground in its vicinity, not the lowest, to ensure the

sees 51.47 next to restored level of have followed the passage of horse

and cart in fields (now

all weathers, indicating that the restored level of the adjacent underlain with ash) is too high. (Save Radley lakes has

commissioned contour, in the s u r v e y s o f t h e o r i g i n a l l a n d s u r f a c e t o t h e n o r t h o f t h e r e g i o n l a b e l l e d D 2 a n d h a s f o u n d 2 4 , 2 5 i t t o b e a r o u n d 52.3m 52.0m 25 AOD. to be Levels on the, now eroded, railway track, now a typically around 52.1 – 52.2 m AOD south of cycleway, were found Lake F.) Moreover, the

restored Contour because does it?

contour lines appear to terminate at the disused railway track. lines do not end. Why are no heights shown on the track? Answer: it is lower and it doesn’t do to draw attention to that unpalatable fact, When the track was laid to connect the branch line with Brunel’s link

to Oxford, it would have and (b) to enable height

been to be

laid on gained

the highest ground (a) to avoid to the east along the track as it

flooding rises up

to meet the Oxford to Didcot main railway. the south of the disused railway was ever

It is inconceivable that the land to higher than the railway itself – a

fact

supported

by

the

1947

flood

envelope

shown

in

Figure

7.

This

shows,

as

do aerial photographs taken railway was flooded, but not

at the time, the railway

that all the land to the south of the itself. The proposed restoration26 is

too

high

and

takes

away

space

on

the

floodplain,

not

just

its

own

volume,

but

also because it blocks the expansion of the floodplain from south to across the tracks. If the OCC and the Environment Agency have agreed restoration levels, they are wrong. It will cause flooding.

north these

The 1947 flood envelope27 reveals a further inconsistency in npower’s argument. If one were to believe their, frankly ridiculous, figure of 52.04m AOD for the peak flood level in 1947, as given in table 2, then one must also believe that all the land south of the disused railway, south of Lakes E and F, was, at that time, below 52.04m – well within anybody’s definition of the floodplain. In any case, accepting, as we do, that the 1947 flood must fall within the risk envelope (it is generally considered, by most flood modellers we have spoken to, to be representative of a flood with a return risk of around 100 years) then it must follow that virtually all of the land south of the disused railway must originally have been on the Thames flood plain as defined by this criterion. This applies whatever the flood levels predicted by any models

24 Ainslie R and Eeles R M G, results of surveys carried out in April and May 2006, private communication. These levels data have been

supplied to the Environment Agency by Save Radley Lakes

25 Guyoncourt, D M and Crowley B J B, Evaluation of Increased Flood Risk as a Consequence of RWE Npower’s Proposal to Dispose

of PFA in Lake E at Radley, Save Radley Lakes report SRL/FP/001.7 (April 2006).

26 These restoration levels were agreed on the basis that they corresponded to the average level of the surrounding land (ES, p.35).

Anyone taking the trouble to walk all the way around lake H/I will notice that the existing fill level is higher than the surrounding land around most of two sides and about level with it around the other two. The average lake surface is therefore above the surrounding land, and this is before any topsoil or overburden is applied.

27 ES, Appendix 7, figure 7.

Page 17 of 23

© SAVE RADLEY LAKES 2006

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