Broughton Flood Action Group Visit to the Alconbury Weald Site
Introduction
At the village flood meeting held in Summer 2021, concerns were expressed about the scale of development planned at Alconbury Weald and what this would mean for flood risk downstream in Broughton. Urban & Civic, the site developer, invited a group of us to discuss these concerns and to visit the drainage works already installed on site. Michael O’Donovan, Richard Probyn, Robin Graham and Dave Cobby attended the meeting on Monday 21 February 2022, which was organised and attended by Hilary Ellis, the Flood Risk Manager for Cambridge County Council.
We discussed the following issues which are most relevant to Broughton, as the development of up to 6,500 homes and commercial properties continues (https://www.urbanandcivic.com/portfolio/strategic-sites/alconbury-weald/).
Will we get increased runoff into the Bury Brook as a result of the development?
The development is committed to limit runoff from all parts of the site to ‘greenfield’ rates. In other words, runoff from all hard surfaces (roads, roofs etc) is stored on site and only released at a rate equivalent to runoff from a natural surface. Given that the airfield already had substantial areas of roofs and hard standing, the development should lead to an overall reduction in runoff, compared with what we get from the land now.
Can the drainage on the site cope with extreme rainfall we get in the future?
Rainfall storage on site is a mixture of Sustainable Drainage Systems (e.g. ponds with reeds to clean the runoff, a cricket pitch with underground storage that doubles as flood storage) and storage within the underground pipe network itself. Runoff which exceeds the storage within the pipes is designed to run down the roads into the storage areas. There is sufficient capacity on site to store the volume of rainfall in a storm that would be expected approximately once every 100 years, and release it slowly.
Will runoff increase until the development is completed?
Site drainage and storage of runoff are some of the first features of the site to be put in. Therefore, as the site is developed, the storage is already in place to absorb the runoff and release it at natural rates. Urban & Civic are clearing the northern portion of the runway at present and anticipate developing this in the next few years.
Who is checking that this all happens as it’s supposed to?
All plans for managing runoff are checked by authorities including Cambridge County Council and the Environment Agency, and approved by Huntingdon District Council. The plans include those to maintain the features, even if the companies involved change. Construction, operation and maintenance can be checked by the authorities against these plans.
Michael with the Urban & Civic team looking at the “bomb store pond”.
What about other development which is proposed upstream of Broughton?
Although any development which occurs within Abbots Ripton parish could impact runoff into the Bury Brook, Broughton Parish Council does not automatically get notified and asked to comment. Therefore, we will seek to work more closely with Abbots Ripton Parish Council so that we are aware of any plans upstream which could negatively impact flood risk in Broughton, and provide comment as appropriate.
We will also consider approaching Huntingdon District Council as the Planning Authority, possibly through our District Councillors, so that we are more directly involved in planning decisions that affect Broughton.
Summary
We felt this was a useful meeting which allayed some fears about how the major development could make flooding worse in Broughton. We formed some relationships which will enable us to constructively raise any concerns in the future. Our thanks to Hilary Ellis, Warren Cull, Andy Brading, Steven Hunter and Andy Fensome.
As a flood action group on behalf of Broughton Parish Council, we will now seek to build similar relationships with Abbots Ripton Estate and Abbots Ripton Parish Council.
If you want any further information, then please contact David Cobby (davemcobby@gmail.com) or others from the village that attended.
Although any development which occurs within Abbots Ripton parish could impact runoff into the Bury Brook, Broughton Parish Council does not automatically get notified and asked to comment. Therefore, we will seek to work more closely with Abbots Ripton Parish Council so that we are aware of any plans upstream which could negatively impact flood risk in Broughton, and provide comment as appropriate.
We will also consider approaching Huntingdon District Council as the Planning Authority, possibly through our District Councillors, so that we are more directly involved in planning decisions that affect Broughton.
Summary
We felt this was a useful meeting which allayed some fears about how the major development could make flooding worse in Broughton. We formed some relationships which will enable us to constructively raise any concerns in the future. Our thanks to Hilary Ellis, Warren Cull, Andy Brading, Steven Hunter and Andy Fensome.
As a flood action group on behalf of Broughton Parish Council, we will now seek to build similar relationships with Abbots Ripton Estate and Abbots Ripton Parish Council.
If you want any further information, then please contact David Cobby (davemcobby@gmail.com) or others from the village that attended.