Drainage

No, there would be no increased flooding to people and property due to this development. The plans include measures that will ensure surface water run off is restricted to greenfield runoff rate.

The surface water management proposal is to be designed to allow for a 40 per cent increase in rainfall intensity (to meet the Environment Agency’s requirements for a potential ‘1 in 100 year rainfall event in the next 100 years’). There will be no sewer flooding within the proposed development in all rainfall events up to and including 1 in 30 year return period storm.

The surface water discharge method will vary depending on location and topography. There are four surface water drainage catchments on the site and surface water disposal from each catchment will be determined in accordance with the SuDS hierarchy to the approval of the Lead Local Flood Authority. To mitigate flood risks on and off site as a result of the proposed development, surface water from the site will be attenuated on site, using a combination of attenuation ponds and underground storage tanks. The attenuated flows will be discharged at greenfield runoff rates to ensure that flood risk is not increased on site and off site. All the SuDS features proposed will be designed in accordance with best practice and the design will be approved by Bristol City Council as the Lead Local Flood Authority.

In addition to attenuation, the levels on the site will be designed to ensure that overland flow routes are directed away from properties to suitable locations within the site such as landscaped areas and attenuation ponds so that no surface water leaves the site at uncontrolled rates for rainfall events up the the 1 in 100 year plus climate change.

These proposals will manage surface water runoff from our site and ensure water is slowed from current levels. Our proposals will ensure peak flows going to School Road from our site are slightly reduced for rainfall events up to the 1 in 100 year intensities.

The ‘wetland meadow’ would not be permanently wet, it would be grassland, not reed beds. Much of the time it would be useable. Wetland meadows is a habitat category.