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
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
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.
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.
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© SAVE RADLEY LAKES 2006