Estimating Financial Flood Damages in Residential and Commercial Regions: A Global Depth-Damage Approach

Abstract The increasing frequency of floods in recent decades has highlighted the pressing need for effective flood management to mitigate damages. Precisely identifying flood-prone areas and quantifying flood damage is of utmost importance, especially in developing countries. In the current study, a 2D hydraulic modeling approach using HEC-RAS is adopted to simulate flood characteristics and flooded area. This research centered around 2 objectives: (1) the development of a regional model for estimating flood damage in residential and commercial zones; (2) the assessment of global depth-damage functions in a western region of Iran. The findings indicated a strong correlation (correlation coefficient > 0.81) between modeled and observed damage losses in residential, commercial and agricultural areas. In situations where observational data were lacking, the Asia and Global depth-damage curves proved to be valuable tools for estimating flood damages in these areas. Furthermore, the evaluation of methods for converting relative damage into monetary value demonstrated that incorporating spatial variations in building size significantly reduced the error in damage estimation caused by floods, by approximately 77%. Although, the use of the reconstruction/renovation cost coefficient tended to underestimate damages in areas with depths exceeding one meter, it showed acceptable performance in estimating flood damages for depths below one meter (absolute relative error = 7.1%). In summary, the Asia and Global depth-damage curves can serve as suitable functions for estimating economic losses in floods, especially in data-limited areas or regions lacking standardized damage functions like Iran. This can provide more reliable estimates of flood damages and aid in better flood management strategies, thereby contributing to improved disaster preparedness and response.