Linking climate, hydrological and hydrodynamic models to understand future flood hazard

Abstract

Flooding is a natural phenomena that affects millions of people around the globe every year. Huge efforts are made to protect against flood impacts, however future flood risks due to climate change are still uncertain. Flood hazard is the result of precipitation events combined with hydrological processes and floodplain dynamics. These interactions make large scale modelling of flood hazard a complex procedure. Future flood hazard is furthermore complicated by the uncertainties around changes in precipitation projected by general circulation models. This research brings together different modelling components to produce high spatial resolution estimates of flood hazard for the present and possible future climates.

To address this, changes of precipitation simulated by climate models, and associated uncertainties are explored. Using results from five commonly-used modelling activities, this research shows many regions do not show significant changes in mean precipitation between the present climate and 1.5°C global warming for the majority of modelling activities. There is high confidence in changes in maximum 1-day precipitation than in mean precipitation, indicating the robust influence of thermodynamics on extreme precipitation changes. Flood hazard representing extreme events in present and future climates is computed over parts of the Ganges-Brahmaputra-Meghna basin including Bangladesh, and translated into population exposure to flooding. Two different flood modelling approaches are used, including a newly developed flood cascade to translate meteorological drivers into flood hazard. Both flood modelling methods show flood extent increasing as precipitation increases, although the changes depend strongly on catchment and magnitude of the event. In addition, results from a single climate model indicate smaller changes in flooding for events with co-incident flooding for the Ganges-Brahmaputra-Meghna rivers, compared to events for individual catchments. The focus region of Bangladesh and the Ganges-Brahmaputra-Meghna basin, is a vulnerable area, where changes in flood risk will have severe consequences.

Date of Award	23 Mar 2021
Original language	English
Awarding Institution	University of Bristol
Supervisor	Dann M Mitchell (Supervisor) & Paul D Bates (Supervisor)