Comparative analysis of local and large-scale approaches to floodplain mapping: a case study of the Chaudiere River

Floods are among natural disasters that increasingly threaten society, especially with current and future climate change trends. Several tools have been developed to help planners manage the risks associated to flooding, including the mapping of flood-prone areas, but one of the major challenges is still the availability of detailed data, particularly bathymetry. This manuscript compares two modeling approaches to produce flood maps. An innovative large-scale approach that, without bathymetric data, estimates by inverse modeling the bed section for a given flow and a given roughness coefficient through 1 D/2D hydraulic modeling (LISFLOOD-FP). And a local approach, with a detailed coupled 1 D/2D hydraulic model (HEC-RAS) that uses all available information at the bed and floodplain (LiDAR and bathymetry). Both implementations revealed good performance values for flood peak levels as well as excellent fit indices in describing the areal extent of flooding. As expected, the local approach is more accurate, but the results of the large-scale approach are very promising especially for areas lacking bathymetric data and for large-scale governmental programs.

Automated summary

This study compares two modeling approaches for producing flood maps, a large-scale approach and a local approach. The large-scale approach estimates the riverbed profile without using bathymetry data through inverse modeling, while the local approach utilizes all available information, including LiDAR and bathymetry. Both methods showed good performance in predicting flood peak levels, with the local approach being more accurate.