The Importance of Robust Baseline Data on Past Flood Events for Regional Risk Assessment: a Case Study from the Indian Himalayas

According to the Sendai Framework for Disaster Risk Reduction, the understanding of the frequency, magnitude, and impact of recent and past extreme events is a cornerstone for coping with future disasters. Nevertheless, baseline data is often scarce, especially in mountain environments. Here, we show with an example how extending the records of past flooding contributes towards a more robust flood risk assessment in a poorly gauged, but highly populated mountain region in the Indian Himalayas (Kullu district; Himachal Pradesh). Drawing from tree-ring -based evidence of past floods, we reconstruct the occurrence of thirty-three flood events over the last century.

The inclusion of this information in the regional flood frequency demonstrates that the flood hazard is underestimated if only data from gauge stations are considered in this assessment. These outcomes reinforce the idea that comprehensive risk assessments should be complemented with evidence-based data on past extreme floods. Therefore, acquiring qualitative and quantitative baseline information in poorly gauged regions should be prioritized to provide the necessary robust foundation for adaptation planning.