Flood Inundation and Monitoring Mapping in Nigeria Using Modis Surface Reflectance

Abstract

Nigeria is witnessing the effect of climate change majorly through flood events. Recent flood disaster in Nigeria posed a threat on people, communities, institutions as well as ecosystem. Floods are common in Nigeria during the peak of raining season (June – October). Remote sensing images and Geographical Information System (GIS) can be efficient tools to determine flood inundated areas. The study developed the sensitivity of water indices to flood water detection and examine the spatial extent of flood inundation -+using MODIS surface reflectance data in Nigeria. In this context, the study involved the use of land surface water index to assess flooding risk at regional scale in Nigeria by using Moderate Resolution Imaging Spectrometer (MODIS) 8th day time series data for the periods 2010 and 2012. Flood events are developed from Enhance Vegetation Index (EVI), Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Land Surface Water Index (LSWI). In order to limit water detection to cloud conditions, MODIS data cloud mask was used to filter the cloudy conditions. The result showed that the water indices (EVI, NDVI, NDWI and LSWI) were highly effective and sensitive in flood water detection. The maximum extent of flood that occurred in October 2012 was estimated to be 11.14 % while in the flood event of September 2012 the total flood extent was 13.15 % of the total land area of Nigeria. The study concluded that, MODIS products had a great advantage in the high-frequent observation while water indices integrated were very effective for flood inundation mapping technique using MODIS surface reflectance products for the entire country of  Nigeria.