Modelling the impacts of fine-scale spatial configuration and connectivity of soil and land use on water, sediment and nutrient flows

English Abstract:

The delivery of water, sediment and chemicals across landscapes and to water bodies is a function of both the biophysical properties of individual landscape elements and their configuration. However, due to computational constraints, fine-scale landscape configuration has generally been neglected or grossly simplified in hydrological modelling. In this talk, we demonstrate a new approach designed to be fast-running while maintaining physical consistency and fine spatial detail. Hydrology, sediment and chemical routing algorithms are based on physical principles of hillslope flow, taking information on the storage and permeability capacity of elements within the landscape from soil and land use data and honoring physical thresholds, mass and energy balance constraints. Hydrological response units are delineated within the landscape according to similarity of their hydraulic properties, and spatially explicit topographical routing is preserved. Landscape response is then evaluated under different meteorological or climatic events (e.g. flood return periods, rainfall events, droughts), cascading water through the hydrological response units using a “fill and spill” approach. The computational efficiency of the approach combined with its focus on spatial detail allows the impacts of landscape connectivity from subfield level scale to national scale to be analysed simultaneously, and communicates the spatial patterns of mass flow within the landscape at detailed resolutions. Case studies from Wales and New Zealand will be presented in this talk, with a focus on how water, sediment and macronutrient delivery to water bodies is impacted by soil and land use configuration.