The Surface Water Management Plans (SWMPs) outline an assessment of surface water flood risk, recognising the flood mechanisms and economic impact to residential and commercial properties across the catchments of Clacton on Sea and Sawbridgeworth.
The surface water flood mechanics and associated risk is poorly understood in Clacton-on-Sea and Sawbridgeworth beyond national scale mapping. The SWMPs are an important component of the County Council’s local flood risk management strategy, required under the Flood and Water Management Act. 2010. SWMPs provide a key tool in helping the Environment Agency and Lead Local Flood Authorities (LLFAs) strategically plan to mitigate surface water flood risk in the respective catchments.
In-line with DEFRA guidance, the SWMP adheres to the four-phase approach of delivery. 1. Preparation - identify need for a SWMP study, its scope and a partnership for its delivery. 2. Risk Assessment – data collection, review and creation of an Integrated Urban Drainage (IUD) model to map and communicate flood risk. 3. Options Appraisal – short-listing preferred mitigation measures and investigating the economic feasibility of the schemes. 4. Implementation and Review.
The creation of an IUD model for the two catchments using the latest hydrological guidance, to inform the rainfall application in the model provided an innovative approach in assessing surface water flood risk. ReFH2.3 was used to calibrate rainfall and runoff to local catchment soil conditions. Sensitivity analysis was undertaken to quantify the variation in model outputs based on adjustments to blockage, floodplain roughness and tidal boundaries where appropriate.
Predicted property counts and economic damage estimation for the baseline and mitigation scenarios have been completed to understand potential benefits within the identified Critical Drainage Areas (CDAs). The proposed mitigation measures included flood attenuation basins and bunds and Property Level Protection. This information has been used to rank the potential benefit cost ratios of schemes within the respective CDA’s across both catchments, to aid in future strategic decisions around the allocation of available funds.
Surface water flood modelling study to determine baseline flood risk through a rural village which is located downstream of a proposed Power Company development site.
Local governments in South East Queensland that contain over a certain population are required by the recently revised Environmental Protection (Water) Policy 2009 to develop and start implementing a Total Water Cycle Management (TWCM) plan before 1 July 2012.
We were engaged by ERA to develop a water quality management framework for mine closure. The broad aim of the project is to develop a practical and transparent management framework to assess effects of contaminants of potential concern on receiving environments during the closure phase, with an initial focus on magnesium.
Following on from our role in assisting Stockland to carry out environmental assessments and obtain federal approval for the project, we have been responsible for the planning and design of the stormwater quality and flood risk management strategy for the Aura site as well as on-going surface and groundwater monitoring.