Potential flood risk under climate change: a local assessment in the absence of damage data

Abstract A method is proposed for assessing flood risk changes for a local river reach under projected climate change scenarios. Such assessments are hampered by a lack of flood damage data, which makes it impossible to use traditional approaches based on damage-flow relationships derived from actual floodplain inundation. Typically, information regarding future floodplain development, essential for climate change impact studies of flood risk, is also unavailable. For a local reach of the Lena River near Yakutsk, we developed a method to assess potential risk within the flood zone. It is based on the Expected Annual Damage (EAD) model and, in the absence of actual damage data, utilizes a set of indices summarizing the impact of flow on structural damage. The traditional EAD model was modified to account for the combined effects of flow depth and velocity, simulated for the river floodplain section using a high-resolution two-dimensional hydrodynamic model. Annual peak flow changes at the inlet of the river section were calculated using a regional hydrological model driven by data from GCMs ensemble. It was found that, even under the low-emissions SSP1-2.6 scenario, potential risk could increase by 23–73%, depending on the level of structural damage. Under the SSP5-8.5 scenario, the risk of catastrophic structural damage would rise by 70%, while minor damage risk would more than triple. The proposed approach can provide insight into the impact of climate change on potential flood risk at a local site in the absence of the damage data required for traditional risk assessment methods. ​