White Cart Water flows through the south side of Glasgow and has a long history of inflicting devastating flooding to the homes and businesses along its suburban banks.
Glasgow City Council embarked on the White Cart Water Flood Prevention Scheme, which used the Flood Modeller 1D solver, to provide a sustainable, environmentally friendly solution to the flooding problem, comprising modest urban flood defences, in conjunction with attenuation storage in the catchment.
As it flows through Glasgow the White Cart Water collects two major tributaries, the Auldhouse and Brock Burns, contributing to a catchment area of 229km2 at Hawkhead downstream of Glasgow city boundary. However, it is the 106km2 catchment at Overlee, as the White Cart Water enters the city, that has been the main focus of efforts to control the flooding problem.
The Overlee catchment is particularly compact with a dense network of watercourses. It is only 12km from the edge of the catchment to Overlee, and the urban river can rise to damaging levels after just a few hours of heavy rain.
Within the Overlee catchment, the White Cart has two major tributaries - the Earn Water joining the main stream at Waterfoot, and the heavily urbanised Kittoch Water which drains much of East Kilbride. In many ways the catchment is well suited to a solution for flooding based on attenuation.
The rapid response of the river means that storage is very effective in attenuating flow, and the relatively sparse extent of settlement allows large storage areas to be contemplated. However, the steep and narrow river valley downstream of Waterfoot rules out a single site that could control the whole catchment and leads to a scheme comprising a number of more remote storage areas.
The one-dimensional catchment model, constructed with flow routing units in our software, was used to assess attenuation scheme options. A total of eleven hydrographs, provided by FEHBDY units, represent flow inputs to the tributaries. The model was calibrated to generate a peak flow of 214m3/s at Overlee from the 200 year return period storm of 9hrs duration.
A range of event files were created for a variety of storm durations and return periods. Storage areas are represented by reservoir units using stage/area data generated from a LIDAR DTM, with QH control units for the outlet controls and weirs for the overflow spillways.
Nine potential flood storage sites were modelled using our 1D solver in the upper catchment. Each scheme was ranked according to its hydraulic efficiency and was assessed and shortlisted at a stakeholder workshop.
The selected schemes were optimised to improve their performance and maximise the storage availability. An update of the urban river model, originally developed in the mid 1980s, was undertaken to ensure it was representative of current conditions, and then it was used to assess the extent and levels of urban flood defences required with each storage option.
The preferred scheme consisted of upstream storage attenuating the White Cart plus two of its major tributaries, combined with urban flood defence walls and embankments. Three storage ponds, located at Blackhouse on the Earn Water, Kirkland Bridge on the White Cart Water and Kittoch Bridge on the Kittoch Water attenuate the 200 year, 9hr flood from 214m3/s to 118m3/s.