Birmingham City Council planning policy for sustainable drainage reports, flood risk assessments and contaminated land risk assessment are driven by environmental conditions and the local authority policy.
Guidance for architects, and developers on flood risk, drainage and phase 1 contaminated land reports is summarised below with links to the key summary documents.
Birmingham was once a major industrial city and as such there is now a legacy of land contamination issues. Consequently, the Council has extensive experience of dealing with land contamination issues associated with its industrial heritage.
Much of the City has not been affected by industrial activity or other contaminative land uses and therefore in order to target resources to areas of greatest perceived risk a strategic approach has been adopted in their Strategy.
Brownfield land (land that’s been previously used for something else, excluding agricultural uses) is increasingly being used for redevelopment.
On land where there’s likely to be significant contamination, it’s important that prior to seeking planning approval you undertake a site investigation on the development site. This will help to identify any contamination that may pose a risk to future occupants of the site.
The site investigation should follow the following, phased approach:
Birmingham state that a site walkover is undertaken for their site investigations of potentially contaminated land, however GeoSmart have worked on previous Sites proposed for development in the area that did NOT require a walkover as advised by the Council. It is advisable that developers correspond with the Council’s Contaminated Land Officer or an environmental consultancy such as GeoSmart to confirm whether a walkover may be required for the initial desk study.
Birmingham City Council
There are twelve Main Rivers in Birmingham and numerous ordinary watercourses and countless unnamed streams and ditches. The river system largely falls within the following Main River Catchments:
All these catchments are regarded as being very responsive due to urban nature of Birmingham.
River Thame Catchment
In Birmingham, the River Tame flows in an easterly direction through the residential and industrial area of Perry Barr, before entering Perry Hall Playing Fields which provides some storage for flood water. From here it continues through Witton where the catchment contains mostly commercial, industrial and residential properties, before passing underneath the “Spaghetti Junction” (M6) road network. Downstream of “Spaghetti Junction” (M6) the River Tame flows underneath the M6, through Gravelly Hill, Bromford and Castle Vale to leave Birmingham just upstream of Water Orton.
River Rea Catchment
On entering Birmingham the River Rea flows through the residential area of Frankley and past the Frankley Balancing Lake which provides offline floodwater storage. Beyond this the River Rea becomes Main River and flows through the industrial and residential areas of Longbridge (notably being culverted through the former MG Rover car plant). It then continues through the predominantly residential areas of Northfield and Kings Norton, where it passes alongside Wychall Reservoir which provides offline balancing. The river then continues through Stirchley and Selly Park which contain a number of commercial, industrial and residential properties. Entering Cannon Hill Park the watercourse becomes an engineered channel with deep brick linings to mirror a canalised cross section to flow through the mainly industrial areas of Highgate, Digbeth, Bordesley, Duddeston and Nechells where it joins the River Tame.
River Cole Catchment
The River Cole flows through Birmingham in a north-easterly direction. On entering Birmingham the river flows through the residential areas of Yardley Wood and Billesley. From here it continues into Sparkhill where it becomes Main River at Formans Road, here the catchment contains commercial, industrial and residential properties. On leaving Sparkhill the catchment returns to predominantly residential properties and with a large green corridor through Hay Mills, Yardley and Stetchford.
Birmingham’s location, as well as topographical and geological characteristics, makes it susceptible to different types of flooding, from rivers, surface water and groundwater, as well as risks from sewers, reservoirs and canals. Flooding is usually caused by natural weather events such as heavy intense storms or prolonged extensive rainfall when the volume of water overflows and inundates land which is usually dry. Due to the nature of the landscape and the urban nature of Birmingham flash floods are most commonly experienced and people often have little time to prepare or evacuate.
Canal Flood Risk
The Birmingham Canal Navigations system extends for approximately 160 miles. The canals converge in the city centre at Gas Street Basin. canals can breach or overtop as a result of elevated water levels from heavy urban runoff. When the canal system is overtopped due to inundation there is little that can be done as the canals are designed to take set amounts of water. There are water control structures to assist in water management; however these are only designed for normal levels of water.
There is a history of flooding in Birmingham; recent years have seen a number of flooding events affecting Birmingham (September 1998, April 1999, June 1999, July 2000, June 2005, June 2007, July 2007, September 2008, June, July, September and November 2012, July 2013 and June 2016). During these events there are reports of flooding from watercourses, surface water, sewers and groundwater.
Site Specific Flood Risk Assessments
A Flood Risk Assessment will be required to accompany planning applications for:
The FRA should identify and assess the risks of all sources of flooding to and from the development, taking into account climate change and demonstrate how the risk will be managed. A FRA will also be required where the proposed development or change of use to a more vulnerable class may be subject to other sources of flooding or where the Environment Agency, Internal Drainage Board and/or other bodies have indicated that there may be drainage problems.
Birmingham City Council
Birmingham City Council recommend that developers consider SuDS at the earliest opportunity seeking pre-application advice where required, as this will aid in mitigating the risk of design conflicts, allow for ease in implementation of SuDS and the greatest cost savings.
The following design process has been identified and should be applied to all proposed developments in Birmingham:
Birmingham City Council
A geological fault crosses Birmingham from the north west to the south east, passing just to the south of the city centre. The underlying impermeable clay predominantly to the south traps water in the predominantly sandstone to the north. Historically this has been a source of water extraction mainly for industrial use. However, this has reduced significantly with the decline in manufacturing industries, which is thought to be a contributory factor to groundwater levels in the City rising back to natural water table levels.
Some work has been done on understanding the nature of the groundwater problem in the city, including some research undertaken by University of Birmingham, and some predictions of future groundwater levels made. The Environment Agency reported that levels are stabilising, however, some property owners are unaware that there has always been water under floors or in cellars. More long-term monitoring data is needed to assess the long-term implications for Birmingham.