An assessment of short–medium-term interventions using CAESAR-Lisflood in a post-earthquake mountainous area

Abstract

Abstract. The 2008 Wenchuan earthquake triggered rapid local geomorphic changes, shifting abundant material through exogenic processes and generating vast amounts of loose material. The substantial material movement increased the geohazard (flash floods, landslides and debris flows) risks induced by extreme precipitation in the area. Intervention measures such as check dams, levees and vegetated slopes have been constructed in specific locations to reduce sediment transport and thereby mitigate the impact of ensuing geohazards. This study assessed the short–medium-term effects of interventions, including multiple control measures, in a post-earthquake mountainous region. Taking the Xingping valley as an example, we used CAESAR-Lisflood, a two-dimensional landscape evolution model, to simulate three scenarios, unprotected landscape, present protected landscape and enhanced protected landscape, between 2011 and 2013. We defined two indices to assess the intervention effects of the three scenarios by comparing the geomorphic changes and sediment yields. The results show that the mitigation measures are effective, especially the geotechnical engineering efforts in combination with ecological engineering in the upstream area. The spatial patterns of erosion and deposition change considerably due to the intervention measures. Additionally, the effectiveness of each intervention scenario shows a gradual decline over time, mainly due to the reduction in the reservoir storage capacity. The enhanced scenario performs better than the present one, with a more gradual downward trend of effectiveness. The simulation results evaluated the ability and effectiveness of comprehensive control measures and will support optimal mitigation strategies.