Using a landform evolution model to study ephemeral gullying in agricultural fields: the effects of rainfall patterns on ephemeral gully dynamics

Autor: Sagy Cohen, David Hoober, Tal Svoray
Rok vydání: 2017
Předmět:
Zdroj: Earth Surface Processes and Landforms. 42:1213-1226
ISSN: 0197-9337
DOI: 10.1002/esp.4090
Popis: Water driven soil erosion is a major cause of land degradation worldwide. Ephemeral Gullies (EGs) are considered key contributors to agricultural catchment soil loss. Despite their importance, the parameters and drivers controlling EG dynamics have not been adequately quantified. Here we investigate the effects of rainfall characteristics on EGs, using the physically based Landform Evolution Model (LEM) CAESAR-Lisflood. An initial goal of this study was to test the feasibility of using a LEM to estimate EG dynamics based on easily obtainable and moderate spatial resolution (2x2 m) Digital Elevation Model (DEM). EG evolution was simulated for two rainfall seasons in a 0.37 km2 agricultural plot situated in a semiarid catchment in central Israel. The 2014 rainfall season was used to calibrate the model and the 2015 season was used for validation. The model overall well predicted the EG network structure and average depth but tended to underestimate the EG length. Next, the effects of rainfall characteristics on EG dynamics were investigated by comparing simulations employing seven rainfall scenarios. Four of these scenarios differ in their overall rainfall volume relative to observed precipitation (+20%, +10%, -10%, -20%). The remaining three scenarios vary in the temporal distribution of rainfall during each storm, allowing us to isolate the effect of rainfall intensity on EG evolution. The results show that: (1) EG dynamics strongly correlated to changes in rainfall volume; (2) small scale morphological behavior varies between rainfall scenarios, resulting in different meandering and connectivity variability; (3) EG evolution is divided into two main stages: an initial rapid development occurring after the first two weeks of the rainy season, followed by a stable development period; (4) a 12 mm hour-1 intensity threshold was observed to initiate and, later, modify EGs; and (5) inner storm rainfall variability can have a considerable effect on EG evolution. This article is protected by copyright. All rights reserved.
Databáze: OpenAIRE
Externí odkaz: