摘要：The Environment Agency has recently completed research looking at rainfall runoff assumption within national scale surface water flood mapping in England and Wales. In particular, the research focussed on the use of a single drainage rate parameter (x mm/hr) to represent the water removed by sub-surface drainage system. The research project developed a method for varying the drainage rate from the national default using local knowledge. We concluded that this approach was valid for the current generation of national scale flood maps. However, we also identified that there is very little scope to develop the approach further. Instead we suggest that new methods need to be developed to support future improvements to national scale surface water flood mapping.
