Hydrology & Hydraulic Modelling
Welshpool Flood Risk Mapping
Keywords: River Modelling (FEH, ISIS-TUFLOW), Strategic Flood Risk Mapping,
ISIS TUFLOW model results for Welshpool
Client, Architect & Other Organisations
Capita Symonds
Environment Agency
Powys County Council
Description
In common with many other urban rivers the Lledan Brook in Welshpool has been gradually covered and culverted to accommodate residential and commercial development in the centre of the Welshpool. Houses, shops, the mill, library, livestock market and roads have all been built over or directly adjacent to the culvert.
Following the development of an ISI-TUFLOW model of the Lledan Brook for the Welshpool Project Appraisal Study for Powys County Council, the Environment Agency appointed Capita Symonds and Edenvale Young to extent the model with a view to updating the flood mapping for Welshpool.
Addiional topographic survey survey was comissioned which enabled the model of the Lledan Brook's to be extended to to its confluence with the River Severn and linking to an existing iSIS model of the river. In addition, the representation of the Mongomery Canal was improved giving improved understanding of overtopping into the canal and spillage from the canal. Flood outlines for a range of return periods were generated including the 1 in 100 year, 1 in 100 year climate change condition and the 1 in 1000 year events. The generation of these outlines lead to a significant alteration in the assessment of flood risk to Welshpool.
The Welshpool ISIS-TUFLOW model was been used to: prepare the Unitary Development Plan for Powys County Council; prepare a developer led FCA for the Smithfield site in Welshpool and derive flood forecasting data for a new gauge installed on the Lledan Brook.