Flood hazard mapping from satellite optical imagery

Over last decades we have witnessed the upward global trend in natural disaster occurrence. Hydrological and meteorological disasters are the main contributors to this pattern. It should be noted that in recent years flood management has shifted from protection against floods to managing the risks of floods (European Flood risk directive) [1]. To enable flood risk assessment, corresponding flood hazard and flood risk maps should be developed. Flood risk is a function of two arguments: hazard probability and vulnerability. In other words, risk is a mathematical expectation of vulnerability (consequences) function [2]. Flood probability density is to be estimated in order to produce flood hazard maps. Usually, this is done through hydraulic modeling of a peak flow. But running such models faces many uncertainties due to the lack of hydrological and other required data, their incompleteness and imperfection. The use of space-borne remote sensing data to flood risk mapping is a complement approach to the existing flood modeling techniques [3].
In this paper we propose a novel approach to flood hazard mapping by processing and analyzing a time-series of satellite data and derived flood extent maps. This approach is advantageous in cases when the use of hydrological models is complicated by the lack of data, in particular high-resolution DEM. Two approaches are investigated for generating flood extent maps for each year: by selecting an image with date of acquisition closest to the day when the maximum discharge was recorded, and integrating all flood extent maps available for the year. Due to the cloud cover and shadows the former method tends to miss areas that were flooded during the flood season, while the latter accounts for all areas that were flooded. Each pixel of the yearly flood extent map is viewed as Bernoulli distribution value, and maximum likelihood method was applied to estimate a success probability from sampling set. This parameter shows probability of inundation, and can be viewed as flood probability density function. Also, we believe that the derived flood extent maps will be very valuable in validating hydrological models once high-resolution DEM is available.
References.
1. Mostert E., Junier S.J. The European flood risk directive: challenges for research // Hydrology and Earth System Sciences Discussions, 2009, Vol. 6, N 4, pp. 4961-4988.
2. Kussul N.N., Sokolov B.V., Zyelyk Y.I., Zelentsov V.A., Skakun S.V., Shelestov A.Yu..Disaster Risk Assessment Based on Heterogeneous Geospatial Information // Journal of Automation and Information Sciences, 2010, Volume 42, Issue 12, pp. 32-45.
3. Schumann G., Di Baldassarre G. The direct use of radar satellites for event-specific flood risk mapping // Remote Sensing Letters, 2010, Vol. 1, N 2, pp. 75-84.