River Eden/Carlisle flood forecast modelling

River floods can cause loss of life, devastating damage to properties and adverse economic and environmental impacts. Although flood risks cannot be completely eliminated, real time flood forecasting models can help to provide timely flood warnings with an adequate lead time for the public to minimise flood damages. Real time flood forecasting is an important and integral part of a flood warning service, and can help to provide more accurate and timely warnings to residents, businesses and emergency services. Depending on catchment characteristics and catchment response to rainfall, various types of flood forecasting models, including correlations, simple trigger flood forecasting and real time catchment-wide integrated hydrological and hydrodynamic models may be adopted. These models provide flow and level forecasts at the selected key locations (known as Flood Forecast Points), which are usually located along major rivers or on streams near urban areas that have a history of flooding. The catchment-wide integrated hydrological and hydrodynamic modelling approach provides a more robust and sophisticated flood forecasting, since hydrological rainfall runoff processes and the interaction of river channel and floodplain hydrodynamic processes are explicitly simulated. Following severe flooding in January 2005, Atkins have developed a sophisticated and efficient Eden/Carlisle hydrodynamic flood forecasting model for real time use. The Eden/Carlisle flood forecasting model consists of a hydrological component, in which flood discharges are estimated from rainfall measurements and forecasts, and a hydrodynamic component, in which the water levels along the entire river network are calculated. The Eden/Carlisle flood forecasting model (with 1100 nodes), converted from an existing flood defence strategy model originally also developed by Atkins, is robust and stable, incorporates the key hydraulic features of the strategy model, and retains all of the originally modelled floodplains within the required model extents. This paper will describe the development of the Eden/Carlisle flood forecasting model focusing on the hydrodynamic component, its typical model runtime performance and model validations.