"The River Ivel catchment is a fast responding catchment meaning it is vulnerable to flash flooding following a significant rainfall event." (Central Beds report CB/FLO/15/09003)

Currently (and for the last 60 years since my family have lived here) Radwell has NOT suffered from flooding, but in wet winters sometimes it does come close to it.

The proposed developments in Baldock plan to add c. 3200 new homes, all of which are in the River Ivel catchment. This infers the development is likely to significantly affect Radwell through increased water flows both from runoff and sewage treatment outfall.

Apparently no Surface Water Management Plan (SWMP) study has been conducted despite the fact that the proposal is to nearly double the size of the Baldock urban area which by any measure must represent a massive increase in flood risk to areas downstream of the catchment.

River flow at Radwell Mill has been measured to vary between 3.5 and 16 Megalitres(Ml)/day (oct 2015 - oct 2016, Affinity Water study).

Treated water:
In the absence of any alternative proposals, it is reasonable to assume the treated water from the developments will go into the River Ivel. On the basis of 2.3 persons per houshold (2011 census), annual water consumption of 110 m3 per houshold/annum (consumer council for water) and 3200 new households this represents an increased output of treated water into the Ivel of some 352 Ml per annum, increasing flow by between 6% and 27%.

Runoff:
"Developing a green field site may result in 10 times the runoff during extreme rainfall" (Woods-Ballard et al 2007). The plan mentions "Sustainable Drainage Systems (SuDS) and other appropriate measures" but these are in large part merely a 'buffer' of limited capacity and not capable of restricting flow for extended periods of wet weather when the river Ivel is already close to capacity. It is therefore easy to envisage that a development of this size is highly likely to lead to flooding in Radwell and other villages (eg Stotfold) downstream. This happened as recently as July 2015 and again in June 2016 when extreme rain events in Letchworth (c. 25mm in 90 minutes) overwhelmed Pix Brook and flooded houses in Stotfold.

25mm (c. 1 inch) of rainfall over 91 Ha is 22 Ml of water. The 5% runoff expected from the green field site would be 1.1 Ml, the runoff from the same area as residential development could be expected to be between 30% (6.8 Ml) and 60% (13 Ml) representing a potential increase of between 5.5 and 12.5 Ml of runoff in a single event, this will increase flow by between 78% and 157% representing a very serious risk of flooding.

Pollution:
Radwell lake is already deemed an area of "Wildlife and Nature policy 14" and we work hard to keep it nice. The massively increased runoff is likely to increase temperatures in our river, harming fish and other organisms; A sudden burst of runoff from a rainstorm can cause a fish-killing shock of hot water. Salt used to melt ice and snow on pavements and roads in the new developments will further contaminate our river.

Oil and other hard-to-monitor pollutants will get into our river from the newly developed areas. This already happened when the SuDS ponds associated with runoff from the A1(M) built in 1966 silted up after only 25 years of service and we began to see an occasional oil film (on one occasion a large quantity of it) polluting our river. Eventually the ponds were dredged at considerable expense because the silt was classified as hazardous waste.