Monitoring of Seasonal Flooding in the Okavango Delta using EO-1 Data

Located in northwestern Botswana and fed by the Okavango River originating in Angola's western highlands, the Okavango Delta is the world’s largest inland delta. The floodwaters require approximately nine months to flow from the source to the bottom of the Delta due to the extremely low topographic relief. During the peak of flooding, the delta’s area can expand to over 16,000 square kilometers, almost doubling the 9,000 square kilometers during the dry season. Investigation of the hydrologic cycle of the Okavango is relevant to studies ranging from fundamental research in climate change to exploration for groundwater to alleviate water shortages faced by local villages. Because the extent and inaccessibility of many areas of the Delta, the application of remote sensing technology is extremely attractive, if it can be shown to effectively map important landcover and geomorphological characteristics (or their surrogates). While results of previous investigations of the capability of multispectral sensors for characterizing drying gradients [1] were promising, the increased dynamic range and additional bands of ALI data potentially provide greater capability for mapping flooding events and characterizing the ecological changes that are rapidly occurring in the Okavango Delta due to climate change and anthropogenic impacts. Further, Hyperion hyperspectral data should provide even greater discrimination of complex vegetation assemblages and improved characterization of seasonal changes in spectral response of vegetation to the annual flooding event. A series of eight near cloud-free EO-1 ALI and Hyperion acquisitions were obtained over Chief’s Island (located in the center of the Delta) spanning the 2001 dry and flooding seasons. The extent of the flood event was mapped using ALI, and the seasonal variation in spectral response of vegetation was determined using ALI and Hyperion. The capabilities of ALI and Hyperion for mapping landuse/landcover change in the Delta are being investigated and compared to Landsat.