The Role of Spatio-Temporal Resolution of Rainfall Inputs on a Landscape Evolution Model

Abstract:

Landscape Evolution Models are important experimental tools for understanding the long-term development of landscapes. Designed to simulate timescales ranging from decades to millennia, they are usually driven by precipitation inputs that are lumped, both spatially across the drainage basin, and temporally to daily, monthly, or even annual rates. This is based on an assumption that the spatial and temporal heterogeneity of the rainfall will equalise over the long timescales simulated.

However, recent studies (Coulthard et al., 2012) have shown that such models are sensitive to event magnitudes, with exponential increases in sediment yields generated by linear increases in flood event size at a basin scale. This suggests that there may be a sensitivity to the spatial and temporal scales of rainfall used to drive such models.

This study uses the CAESAR-Lisflood Landscape Evolution Model to investigate the impact of spatial and temporal resolution of rainfall input on model outputs. The sediment response to a range of temporal (15 min to daily) and spatial (5 km to 50km) resolutions over three different drainage basin sizes was observed. The results showed the model was sensitive to both, generating up to 100% differences in modelled sediment yields with smaller spatial and temporal resolution precipitation. Larger drainage basins also showed a greater sensitivity to both spatial and temporal resolution. Furthermore, analysis of the distribution of erosion and deposition patterns suggested that small temporal and spatial resolution inputs increased erosion in drainage basin headwaters and deposition in the valley floors. Both of these findings may have implications for existing models and approaches for simulating landscape development.