Multiscale impacts of land use/management changes on flood response in the River Hodder catchment, North-West England
Geris, Josie Regina Catharina
PublisherUniversity of Newcastle Upon Tyne
MetadataShow full item record
There is substantial evidence that land use/management changes (LUMCs) can impact runoff generation at the local scale; however, it is unclear how these impacts are modified as they travel through the river channel network to affect downstream catchment flooding. There is a need for data from multiscale monitoring studies in catchments undergoing known LUMCs to assess the extent to which impacts can be detected at increasing catchment scales. This understanding is needed in developing reliable methods for assessing the potential of rural based flood prevention and mitigation measures, urgently required by catchment planners. The aim of the present study is to generate and analyse a new multiscale dataset which will serve to gain a better understanding of the effects of local LUMCs on catchment response at increasing scales. This study investigates the impacts of recent LUMCs (drain blocking, stocking density changes, and afforestation) in the headwaters of the River Hodder (261 km²), North-West England, UK. An unusually dense nested monitoring network (28 stream gauges) was set up at scales ranging rom ~1 ha to 261 km². Data Based Mechanistic (DBM) modelling and a simple Storage Discharge Detection (SDD) model were used to compare pre- and post-change hydrographs at increasing scales in an effort to detect short-term change signals and their propagation to larger scales. A novel physically based Model for Upland Runoff Storage and Flow Fields (MURSAFF) was developed to further investigate the short- and long-term impacts of LUMC in complex landscapes at the micro catchment scale (~1 km²). The results were integrated into a semi-distributed catchment impact routing model to explore the effects on the downstream catchment response. No statistically significant evidence was found in the DBM and SDD results to suggest that any of the LUMCs had a short-term impact on catchment response at scales from 1 km² up to the Hodder catchment scale (261 km²). This is attributed to the proportion of area affected by change, the timescale of impacts, and the natural variability in catchment response. Short-term small scale (< 1 km²) field observations and MURSAFF predictions of the impacts of drain blocking involved an increase in the local storage and change in the flow fields. However, these changes are insignificant at the micro catchment scale. The MURSAFF simulated impacts of reductions in stocking density involve attenuation of the flood hydrograph mainly. Predictions of the downstream effects suggest they will be relatively small and different for each storm, with the lack of internal synchronisation of the sub-catchment responses and the natural variability therein being dominant factors in determining the impacts on the catchment outlet response. These predictions are consistent with the failure to detect any significant impacts in the post-change records.