Towards understanding links between rural land management and the catchment flood hydrograph

The nature of causal links between land management in rural river catchments and the flood hydrograph is investigated. A catchment can be represented as a mosaic of tiles with different land use, land management, and soils. Over the mosaic, the causal links vary with the physical properties of the land and channel drainage network, and with the management practices and spacetime variations in rainfall and evaporation. The river Hodder catchment in northwest England is represented using a custom-designed semi-distributed rainfall-runoff model. An adjoint, reverse algorithmic differentiation, version of the model is then used to find the sensitivity of the peak flow rate at the catchment outlet to the model parameters controlling runoff generation. Using this novel approach, the links between changes in land management and the impact on the peak flow rate are investigated by decomposing the impact in space to give maps that show the sources of impact, tile by tile. The method works quite well for the Hodder catchment, especially for rainfall events in the autumn and winter. Its strengths and weaknesses are discussed. Copyright (c) 2012 Royal Meteorological Society