Numerical analysis of river flood defences

Abstract

Flooding is the most costly natural hazard in the UK and impacts are increasing because of urbanization and climate change. Experiences in developed countries (UK and Europe) have demonstrated that traditional hard engineering solutions are not solving the problem. Decision makers in UK and EU are seeking to develop soft engineering solutions focused on planning, catchment management and working with natural processes, with positive results. This experience can be useful in developing countries in order to avoid past mistakes made in developed countries. 1D modelling of an ideal geometry has been used to analyse the effect on water levels in both upstream and downstream, including some flood defences (channel straightening, widening, dredging, flood levees and flood storage areas). The results show that hard flood defences are no better than soft solutions. In particular, off-channel solutions such as flood storage areas or wall/dykes, perform better than in-line solutions.