Catchment Runoff Response to Land-Use–Driven Soil Impacts: Modelling a small torrential catchment in the Wienerwald Flysch Zone using Raven

Small torrential catchments respond rapidly to critical precipitation or rainfall events, which can pose serious natural hazards to downstream settlements. Natural water retention - primarily through forest interception and soil infiltration - can reduce runoff peaks. Its effectiveness is strongly shaped by human land use and respective changes. Climate change additionally impacts natural water retention by shifting vegetation patterns and increasing the occurrence of heavy rainfall events. To evaluate the impact of changing catchment characteristics, the first step is to gain a better understanding of interrelated processes and their impact on runoff dynamics.

In this study the hydrological modeling framework Raven (Craig et al. 2020¹) was applied to model hydrological processes in a small, forested catchment (~0.5km²), which is a tributary of the “Wienfluss” and is dominated by clayey soils. Hydrological response units (HRU) were delimited based on calculated sub-catchments, topography, land use, vegetation, and a soil classification geostatistically interpolated from a grid (75 × 75 m) of 104 core samples. Runoff is measured at a weir located at the catchment outlet and serves to validate the model runoff. Meteorological data provided by the Federal Forest Research Centre (BFW) were used as input over a warm-up period, as well as for the simulation period of two years (2022-2023). Raven, as a modular, mixed lumped/semi-distributed model framework, offers a wide range of flexible algorithms that allows users to adapt the configuration of represented hydrological processes according to specific catchment characteristics. We focus on understanding the interrelation of different processes, and in particular, the dynamics between soil properties, storage, interflow, baseflow, and surface runoff. Further applications of the model are planned to investigate the influence of soil compaction from heavy forestry machinery, including changes in soil functions (infiltration, storage, drainage) and associated greenhouse-gas emissions (CO₂, N₂O, CH₄).

 

¹Craig, J.R., Brown, G., Chlumsky, R., Jenkinson, R.W., Jost, G., Lee, K., Mai, J., Serrer, M., Sgro, N., Shafii, M., Snowdon, A.P., Tolson, B.A., 2020. Flexible watershed simulation with the Raven hydrological modelling framework. Environmental Modelling & Software 129, 104728. https://doi.org/10.1016/j.envsoft.2020.104728