An Efficient Modeling Approach for Probabilistic Assessments of Present-Day and Future Fluvial Flooding

Abstract

Risk-informed flood risk management requires a comprehensive and quantitative risk assessment, which often demands multiple (thousands of) river and flood model simulations. Performing such a large number of model simulations is a challenge, especially for large, complex river systems (e.g., Mekong) due to the associated computational and resource demands. This article presents an efficient probabilistic modeling approach that combines a simplified 1D hydrodynamic model for the entire Mekong Delta with a detailed 1D/2D coupled model and demonstrates its application at Can Tho city in the Mekong Delta. Probabilistic flood-hazard maps, ranging from 0.5 to 100 year return period events, are obtained for the urban center of Can Tho city under different future scenarios taking into account the impact of climate change forcing (river flow, sea-level rise, storm surge) and land subsidence. Results obtained under present conditions show that more than 12% of the study area is inundated by the present-day 100 year return period of water level. Future projections show that, if the present rate of land subsidence continues, by 2050 (under both RCP 4.5 and RCP 8.5 climate scenarios), the 0.5 and 100 year return period flood extents will increase by around 15- and 8-fold, respectively, relative to the present-day flood extent. However, without land subsidence, the projected increases in the 0.5 and 100 year return period flood extents by 2050 (under RCP 4.5 and RCP 8.5) are limited to between a doubling to tripling of the present-day flood extent. Therefore, adaptation measures that can reduce the rate of land subsidence (e.g., limiting groundwater extraction), would substantially mitigate future flood hazards in the study area. A combination of restricted groundwater extraction and the construction of a new and more efficient urban drainage network would facilitate even further reductions in the flood hazard. The projected 15-fold increase in flood extent projected by 2050 for the twice per year (0.5 year return period) flood event implies that the “do nothing” management approach is not a feasible option for Can Tho.

Flood Damage and Shutdown Times for Industrial Process Facilities: A Vulnerability Assessment Process Framework

“…For flood hazards, it can therefore be understood to mean "susceptibility to damage" posed by floodwaters, with the inundation level acting as the independent variable. Additionally, floodwater type (e.g., saltwater, freshwater, contaminated water) and duration of inundation are also key parameters in the ultimate effects of flooding (Ngo et al, 2022).…”

Flood damage and shutdown times for industrial process facilities: a vulnerability assessment process framework

“…For flood hazards, it can therefore be understood to mean "susceptibility to damage" posed by floodwaters, with the inundation level acting as the independent variable. Additionally, floodwater type (e.g., saltwater, freshwater, contaminated water) and duration of inundation are also key parameters in the ultimate effects of flooding (Ngo et al, 2022). In turn, a thorough vulnerability assessment involves examining system elements and design, as well as identifying component failure modes in response to a given set of threats (Baker, 2005;Peterson et al, 2019).…”

Cloud Modelling of Property-Level Flood Exposure in Megacities

“…Many studies simulating surface flow have been conducted for small urban catchments [29][30][31][32][33][34][35][36][37][38]. Other larger-scale studies have focused on the flood risk from rivers (fluvial flooding) [39][40][41][42]. The first attempt to simulate the flood impacts in European cities was presented by Guerreiro et al [43], where they calculated the percentage of urban areas flooded for 571 cities in Europe with a spatial resolution DTM of 25 × 25 m for nine different rainfall events, but concluded that the low resolution of the DTM imposed major limitations due to not representing flow paths accurately.…”