Dredging abandoned, saving Marlow sacrificing Bisham

Mike Post made this Freedom of Information request to Environment Agency

This request has been closed to new correspondence from the public body. Contact us if you think it ought be re-opened.

The request was partially successful.

Dear Sir or Madam,

There has been no regular dredging of the Thames near Marlow since 1996.

Can you please confirm that this failure to dredge has not increased the risk of flooding in Marlow and Bisham? It seems to be basic physics that if an engineered watercourse is allowed to become shallow, it will have less water-carrying capacity and will over-top its banks with less volume flow. Can you please provide me with the scientific justification for your response?

There is said to be a proposed system of bunds on the Marlow side of the Thames to protect areas of Marlow built in the flood plain. Can you please provide me with details of the proposed defence system and confirm that these proposed defences will not exacerbate the risk of flooding in Bisham? Can you please provide me with the engineering justification for your response?

Thank you in anticipation.

Yours faithfully,

Mike Post

Enquiries, Unit, Environment Agency

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Dear Enquiries, Unit,

Thank you for your initial response. I look forward to hearing from you.

Yours sincerely,

Mike Post

Enquiries, Unit, Environment Agency

Thank you for contacting the Environment Agency. Please see below
regarding our response times and environmental incident reporting

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Enquiries, Unit, Environment Agency

Dear Mike

Thank you for your enquiry. For your information, your query has been
passed to our local External Relations Team (Planning and Corporate
Services) for attention and they will be in touch with you shortly.

Should you wish to contact them in the meantime, their details are
below. Please quote your Enquiry Ref 090814SS27 in your correspondence
with us.

External Relations
Planning and Corporate Services
Environment Agency
Thames Region, South East Area
Swift House
Frimley Business Park
CAMBERLEY
GU16 7SQ
Tel: 08708 506506

Kind Regards

Samantha Shaw
National Customer Contact Centre
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show quoted sections

Edwards, Marie, Environment Agency

1 Attachment

Please see attached our acknowledgement of your request.

Regards

Marie Edwards

External Relations Officer

Tel 01276 454427

E-mail [1][email address]

P Did you know - spray taps can reduce water use by 60 - 70% compared with
conventional taps

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Ian Salisbury left an annotation ()

"Dredging the River Thames above Oxford", another inquiry of the E.A., was not (as far as I can see) sent to public relations. I wonder why this one should have been? Ian Salisbury.

Edwards, Marie, Environment Agency

7 Attachments

Dear Mr Post

Please see attached our response to your enquiry.

Regards

Marie Edwards

External Relations Officer

Tel 01276 454427

E-mail [1][email address]

P Did you know - spray taps can reduce water use by 60 - 70% compared with
conventional taps

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Dear Ms Edwards

Thank you very much for your very informative reply to my FOI request regarding dredging of the Thames near Marlow and the Marlow Flood Alleviation Scheme.

Whilst the information you have provided is very informative, you have not responded to my request for confirmation that the failure to dredge since 1996 has not increased the risk of flooding in Marlow and Bisham. I also requested the scientific justification for your response. There is anecdotal evidence that the reach of the Thames immediately downstream of Marlow weir is considerably shallower than in the past. It is obvious that a shallower river can carry less volume flow of water before it floods. Can you please confirm whether or not the Environment Agency has records of the river bed level for this particular short reach of the Thames.

You may be aware that our MP, Theresa May, is to make a visit of inspection later this month.

I note from the five-page Halcrow Dredging Summary, dated July 2009, that dredging has been undertaken near Marlow since the late 1940s “to maintain a navigable channel and to manage flood risk by maintaining the channel flow capacity”. I further understand that the Thames in Marlow has been designated, at least in draft, as a ‘heavily modified watercourse’. Perhaps you can please confirm that this is the case?

With regard to the Marlow Flood Alleviation Scheme, it seems intuitive that groundwater from the Marlow side of the river which is pumped back into the river, rather than being allowed to disperse in the floodplain on the Marlow side, must have an effect on the level of water on the Bisham side of the river and a consequential detrimental effect on properties in Bisham. I should be grateful for the engineering justification (for which I asked in my enquiry) for this not being the case. I should also be grateful for information on the assumptions which have been fed into your models, which I assume are digital rather than physical.

From a purely personal perspective, perhaps the most interesting document is the Halcrow map, reference WNGLDC-913 “Flood Extent After Marlow Flood Alleviation Scheme”, which clearly shows that our family home, Meadow House, is above the 1 in 100 year river flooding both before and after the flood alleviation scheme. I hope that the CD of my photographs of the 2003 flood which I gave to the Agency in 2003 were helpful in constructing this map.

Finally, I should also be grateful for your email address which was transmitted in your reply as a series of ‘x’s and also the email address of Doug Hill.

Thank you in anticipation.

Yours sincerely

Mike Post

Dear Edwards, Marie,

Can you please confirm that you have received and are addressing my reply to you dated 10 September 2009. I am a little confused by the system.

Many thanks in anticipation

Yours sincerely,

Mike Post

Edwards, Marie, Environment Agency

I will be out of the Office until Wednesday 23rd September 2009 . Any
urgent enquiry should be sent to [email address]

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Edwards, Marie, Environment Agency

Dear Mr Post

Sorry for not responding to your e mail sooner. I was out of the office
for a few days.

I forwarded your e mail of Thursday 10th to our Asset Management Team
for a response to your further enquiry.

We will endeavour to supply the information you have requested as soon
as possible. We will aim to send you a full response within 20 working
days of receipt as set out in the Freedom of Information Act. Or for
request under the Data Protection Act, we will send a full response
within 40 working days.

Regards

Marie Edwards
External Relations Officer
Tel no 01276 454427
E mail [email address]

show quoted sections

Dear Edwards, Marie,

Further to my FOI request of 14 August 2009 and my follow up dated 10 September 2009, I should be grateful if you would let me know when I can expect a response.

Yours sincerely,

Mike Post

Edwards, Marie, Environment Agency

Dear Mr Post

Do you have another e mail address I can send the information to?

I have been trying to send you information since last week & again Just
now with a number of Files attached. It keeps being rejected with the
following message.

The following recipient(s) could not be reached:

Mike Post on 13/10/2009 11:21
This message is larger than the current system limit or the
recipient's mailbox is full. Create a shorter message body or remove
attachments and try sending it again.
<EXCCLUS03.PRODDS.NTNL #5.2.3 smtp;450 5.2.3 Msg Size
greater
than allowed by Remote Host>

Regards
Marie Edwards

show quoted sections

Dear Edwards, Marie,

Thank you for the reply. Perhaps you could try my google mail account which has large capacity for attachments. The address is [email address]

Regards

Yours sincerely,

Mike Post

Dear Edwards, Marie,

Can you please confirm that you have received my alternative email address, [email address] ?

Many thanks.

Yours sincerely,

Mike Post

Edwards, Marie, Environment Agency

Dear Mr Post

I have received your e mail & I have attempted to re send the email to
the new address. Unfortunately the same problem occurred. I am going
to try a different method to collate the information & send to you.

Sorry about the delay

Regards
Marie.

show quoted sections

Dear Edwards, Marie,

Thank you for the update. The google mail account has huge capacity.

Yours sincerely,

Mike Post

Dear Edwards, Marie,

Thank you for sending the information to my googlemail account which I have now received. I shall study it before coming back to you in due course. I shall also send an acknowledgement via email to Doug Hill.

Yours sincerely,

Mike Post

Ian Salisbury left an annotation ()

It would be interesting to know what the information is that was sent privately. Would it be possible, Mike, for you to try posting it? Thanks.

Dear Marie Edwards,

Thank you for the information on river surveys of the Marlow to Cookham reach which has arrived by my googlemail account. I should be grateful if you would try resending the information on the Flood Risk Assessment since all the appendices were blank.

You will recall that I asked: “Can you please confirm that this failure to dredge has not
increased the risk of flooding in Marlow and Bisham? It seems to be
basic physics that if an engineered watercourse is allowed to
become shallow, it will have less water-carrying capacity and will
over-top its banks with less volume flow. Can you please provide me
with the scientific justification for your response?

So that comparisons can be made, can you please provide me with similar surveys which predate 1995? I am particularly interested in the large area of river below Marlow weir which is white on the survey maps which seems to indicate that approximately 58% of the river adjacent to the property ‘Marlow Meadows’ may be silted up.

Yours faithfully,

Mike Post

Dear Edwards, Marie,

As requested on my google mail account, here is the message that I sent via the whatdotheyknow website.

Dear Marie Edwards,

Thank you for the information on river surveys of the Marlow to
Cookham reach which has arrived by my googlemail account. I should
be grateful if you would try resending the information on the Flood
Risk Assessment since all the appendices were blank.

You will recall that I asked: “Can you please confirm that this
failure to dredge has not
increased the risk of flooding in Marlow and Bisham? It seems to be
basic physics that if an engineered watercourse is allowed to
become shallow, it will have less water-carrying capacity and will
over-top its banks with less volume flow. Can you please provide me
with the scientific justification for your response?

So that comparisons can be made, can you please provide me with
similar surveys which predate 1995? I am particularly interested in
the large area of river below Marlow weir which is white on the
survey maps which seems to indicate that approximately 58% of the
river adjacent to the property ‘Marlow Meadows’ may be silted up.

Yours sincerely,

Mike Post

Edwards, Marie, Environment Agency

I will be out of the Office until Monday 26 October 2009 . Any urgent
enquiry should be sent to [email address]

Information in this message may be confidential and may be legally
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Dear Edwards, Marie,

Please find below the email that I have just sent to Doug Hill.

Dear Doug

I have finally managed to find time to look at the dredging and survey information that you kindly sent me about the Cookham Reach from Marlow to Cookham on the Thames.

It is striking that between March 2003 and April 2008 an estimated 185,252 cubic metres of silt were scoured from the Reach. It is also extremely striking that the overwhelmingly orange shade of the river indicates that virtually the whole length of the Cookham Reach river bed was between 0.25 metres and 0.5 metres higher in March 2003 than it was in April 2008. In other words, the whole length of the reach was predominantly between 0.25 metres and 0.5 metres shallower in 2003 than it was in 2008.

March 2003, the date of the 2003 survey, was shortly after the flood in January that year which was devastating to several properties in Quarry Wood Road, Bisham including the Compleat Angler hotel. The whole of the Cookham Reach was approximately 0.25 metres to 0.5 metres shallower in early 2003 than it was in 2008. It cannot but be suspected that the Environment Agency’s decision to abandon routine dredging during the eighties and nineties resulted in the whole length of Cookham Reach becoming shallower than desirable. If it is shallower, the river will overflow its banks more quickly, than when it is deeper, like a gutter with its bottom full of rubbish. It appears that by early 2003 the traditional capacity of the whole length of this Reach had been substantially reduced.

Whilst it is reassuring to know that, thanks to self-scouring, the river has (or had in 2008) substantially increased capacity since the 2003 floods, it seems that there is prima facie evidence in the two July 2008 ‘Cookham Reach Erosion and Deposition Charts’ that the Environment Agency’s failure to take measures to maintain the depth of the Cookham Reach up to 2003 may have exacerbated the flooding along that stretch of the Thames in 2003.

We need to know the reason for the apparent self-scouring of the river since 2003. We also need to receive reassurance from the Environment Agency that the river will be regularly surveyed to ensure that the bed-level does not rise again. If the Reach does again become shallow, we would expect suitable, traditional, good-housekeeping measures, such as dredging, to be undertaken, to restore the capacity of the river to its pre-Environment Agency state.

Thank you for your help. As you suggested, I shall send this email to you and copy it onto the whatdotheyknow website.

Kind regards

Mike Post

Yours sincerely,

Mike Post

Ian Salisbury left an annotation ()

For further background information, the BBC Radio 4 Farming Today Programme on Wednesday 9 December 2009 contained an interview with Mr Phil Rothwell, Head of Flood Strategy at the Environment Agency. Hear it on "Listen Again" at http://www.bbc.co.uk/iplayer/episode/b00...

Edwards, Marie, Environment Agency

1 Attachment

Dear Mr Post

Please see attached acknowledgment of the request you sent to Doug Hill
& reference number for your request.

Regards
Marie Edwards

show quoted sections

Dear Edwards, Marie,

Here, for the public record, is the exchange of emails between Doug Hill and me.

Hi Doug

Thank you for your letter.

With regard to meeting up, Jean Garon, who lives on the Cookham Reach just below Marlow weir is abroad at the moment. Perhaps when she returns, and the weather is more clement, we could arrange to meet. As a layman I am struggling with the concept that the river bed can be higher but the river is not shallower for the same water level.

Regards

Mike Post

Dear Mr Post

Dredging on the Thames

Thank you for your email dated 8 December 2009.

I recognise your concerns with regards to the difference in bed levels from March 2003 and April 2008, however, from the survey information available the river does not appear to have got any shallower between 1999 and 2003. This shows that the end of the dredging programme in the mid 1990’s did not lead to a rise in river bed levels prior to the flooding in 2003. Our surveys from 2003 to 2008 show that the river has naturally self-scoured and has lowered it’s bed level compared to 1999 and 2003.

The recorded changes in bed volume and levels depends on the timing of the surveys in relation to periods of high and low river flow. Net changes in bed volumes of up to around 100,000 m3 have been recorded between surveys in some sub-reaches. The recorded annual average net volume changes are typically in the range 10,000 m3 to 20,000 m3 per year in each sub-reach although larger transient variations may be masked for the longer survey intervals.

At present we are carrying out yearly hydrographic surveys on Old Windsor, Bell Weir and Penton Hook reaches, the 3 reaches for which we have more frequent historical data. We will be comparing bed level data with flow measurements to try to understand their connection better.

We shall continue to monitor all reaches frequently using hydrographic data in order to consider the need to dredge. We plan to survey the Marlow to Cookham reach again in 2012/13. It is important that any dredging strategy is well-informed, and takes into account the natural sedimentation and scouring regime of the river, as well as the costs and practicality of dredging and the disposal of the waste.

If you would like to any further information please contact Doug Hill, Thames, Wey and Loddon Asset System Management Team, Flood Risk Management on 01276 454513 or by e-mail [email address].

Yours sincerely

Doug Hill
Team Leader - Asset System Management
Thames, Wey and Loddon

-----Original Message-----
From: Hill, Doug [mailto:[email address]]
Sent: 18 January 2010 12:03
To: Mike Post
Cc: Attfield, Kerry
Subject: RE: Marlow Bisham FOI

Mike,

Sorry for the delay in getting this response to you. I would still like to meet up to go through the report and any issues in a bit more detail and am happy to come over to Bisham. I'd prefer it if we kept numbers to a minimum so that the conversation can be a bit more focused. If you could let me know your availability I can set some time aside.

Many thanks
Doug

Doug Hill
Team Leader - Asset Systems Management
Thames Region - South East Area
01276 454513

From: Mike Post [mailto:[email address]]
Sent: 29 December 2009 10:20
To: Hill, Doug
Cc: Edwards, Marie; Attfield, Kerry; Croucher, Graham
Subject: RE: Marlow Bisham FOI
Dear Doug

Thank you for the email. Can I respond fully some time later in January. I think that some of the Quarry Wood Road residents may wish to be involved and I will be away until mid-January.

Compliments of the season.

Regards

Mike Post

-----Original Message-----
From: Hill, Doug [mailto:[email address]]
Sent: 09 December 2009 09:39
To: Mike Post
Cc: Edwards, Marie; Attfield, Kerry; Croucher, Graham
Subject: RE: Marlow Bisham FOI

Mike,

Thanks for the email, I'll make sure it gets registered here as a FOI request and managed appropriately. I'll get a response to you as soon as possible but it may be worth us sitting down and discussing the issue face to face. I can then produce a response that can be put on the web site. I would also like to see the sand bar that has built up near to the Lock Island.

Thanks,
Doug

Doug Hill
Team Leader - Asset System Management
Thames Region - South East Area
01276 454513

Yours sincerely,

Mike Post

Edwards, Marie, Environment Agency

I will be out of the Office until Thursday 4th February. Any urgent
enquiry should be sent to [email address]

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Edwards, Marie, Environment Agency

Dear Mr Post

Thank you for these copies. I also have copies from Doug Hill.

Regards
Marie Edwards

show quoted sections

Dear Edwards, Marie,

The whole purpose of this website is that the exchanges should be public - there are other riparian owners interested. I should therefore be grateful if you would up load any future emails from the EA on to this site.

Thank you in anticipation.

Yours sincerely,

Mike Post

robin ford left an annotation ()

Interesting.