https://environmentagency.blog.gov.uk/2014/05/26/protecting-water-quality-on-the-parrett-and-tone/

Protecting water quality on the Parrett and Tone

The first glimmer of sun might have appeared in the South West but many on the Somerset Levels are still dealing with the aftermath of flood water devastating their home or business. We ran a flood recovery surgery last week  in North Newton and my colleagues met over 30 residents from communities including Northmoor Corner, Chadmead, Tuckerton, and Bankland to discuss their experiences and how we’ll prepare together for next winter. The 8km dredge we're doing along the Parrett and Tone rivers is just one of the ways to help protect this area. As we dredge to reduce flood risk to people’s homes, lives and livelihoods it’s my role to help this work to go ahead smoothly and look after water quality and the water environment. We have to protect people and the environment, and we want to get it right.

Before the start of the dredge, I was part of the planning process to look at the impact dredging could have on the water environment and what impact had already occurred from the flooding. We analysed a range of existing information around the proposed dredge area and developed a monitoring programme.

Monitoring at Long Load Pumping Station
Monitoring at Long Load Pumping Station

As part of the monitoring programme, I’m particularly watching out for the dredge affecting water quality downstream. To help with this we have staff out on the ground taking water samples and we have a number of automatic water quality monitors across the river network, giving us continuous information on the state of the water environment. This will indicate when and where there is a risk of a pollution incident. I also help review the data and look out for indicators like lower dissolved oxygen levels. This information gives us time to adapt or change our dredge operation to reduce the risk of a pollution incident. So far I’m pleased that our monitors are showing that the water environment has not suffered any long term impact from the recent flooding, and there are no current indications of a risk to water quality from the ongoing dredging. With warmer weather on the way, and dredging operations set to expand, my colleagues and I will be keeping a close eye on our monitoring data

Have you attended one of our community flood events like a dredge drop-in session or a flood surgery? If so, we’d welcome your feedback at: http://feedback1.environmentagency.uk.com/s3/Feedback-survey

8 comments

  1. Harvey Cheetham

    Is it any good dredging the Parrett, although anything will help, when the wharves in Bridgwater are already being damaged by excessive water flow. Clearing the King's Sedgemoor drain, especially at Dunball, may be of greater help. Was the sluice at Dunball open when the floods happened? Why were the Dutch pumps necessary when the tide was out?
    Please log on to http://www.floodsandgravel.co.uk/somerset for further details and to contact me if you require.
    Yours sincerely Harvey Cheetham

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    • Environment Agency

      Hi Harvey. Thank you for your comments. We've passed them onto the local team and will be in touch asap. ^Jo

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      • Peter Austin

        Mr Cheetham, I would have thought that it is obvious that increasing the capacity of the Parrett to it`s 1970`s capacity and clearing build ups of silt which have narrowed the river will help alleviate flooding , by enabling excess water to run out to sea quicker and enable the parrett to carry both incoming tidal water and run-off from upstream, rather than spilling over the banks at such a rate as happened last year.
        . The pumps were used at Dunball to increase the removal of floodwater from the levels to stop it becoming even more flooded , if they hadn`t been used, I`m sure that Bridgwater would have joined the list of flooded communities.

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        • Peter Austin

          I agree that Pinch points where the rivers are narrowed by bridges etc should be sorted quickly.

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    • Environment Agency

      Hello Harvey,

      We have now received a response to your query from our area team, please see below:-

      In response to your questions above, the sluices at Dunball was opened for gravity discharge when water levels were appropriate. On a rising tide the Dunball sluices shut as they are large non-return flaps. When the tide drops, water stored behind these large non-return flaps is released. During this period of ‘tide lock’, the pumps were operated to ensure some discharge, although we know not at the same volume as with gravity discharge. To explain further, under normal circumstances the volume of water passing through these sluices is 70 cubic metres per second (cumecs) by gravity; while the pumps being operated during ‘tide lock’ were moving approximately 10 cumecs of water. We hope this answers your questions.

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  2. Harvey Cheetham

    To Peter Austin at EA. I have just found your blog about my comments on Dunball sluice. Please use Twitter or emails - then I can find you.
    If the sluices pass 70 cumsecs then at 2m/sec the sluices must be 35 sqm in cross section but they only work for 12hrs in the day so assume 20 sqm. Next to the sluice the cross section is approx 160 sqm and KSD itself is 60 sqm ? undredged and it is raining 24hrs a day for several days. How can the sluice be expected to cope?
    The pumps will help but they need to be working before the flood reaches Dunball.
    It appears the sluices were designed to stop the tide entering KSD but not to allow for the exit of flood water - they certainly did not cope this year. What will happen next time?
    Dunball sluice was rebuilt in 1972 - how big was it before and what was there when KSD was first constructed?
    I have just found a picture of the bridge in Bridgwater full to the brim - Bridgwater cannot take any more yet you are hoping the dredging will send more water this way.
    Please make the Parrett sluice as big as the river for the same reason.
    There are a series of "lock" gates on the outfall of the Holderness drain in Hull but these are not wide enough and seem to be stuck in the mud, see web site.

    This might also be the same problem in Stockton-on-Tees and Hull - see web site, and on the River Wiske in Yorkshire.

    May I put this blog on the web site next month if you have no objection.

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    • Environment Agency

      Hello,

      Thanks for your comments which I will pass onto our local area team(s) for there information. Just to let you know Peter Austin is not an Environment Agency employee so we cannot comment on his behalf. Thanks ^Chris

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    • Environment Agency

      Hello Harvey

      Can you please email your contact phone number to southwestenquiries@environment-agency.gov.uk and one of our technical specialists will call you to discuss your questions, and hopefully clarify things for you.

      Thanks Chris

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