Geomorphological-based Remote Sensing and GIS analyses to identify vulnerable zones of forest fire in Zambezi Region, North-eastern Namibia

Abstract

Forest fires are a threat to biodiversity, lives, and livelihoods in many parts of the world. In Namibia, there is growing concern over the increasing frequency and severity of forest fires. The aim of this research was to map out fire-vulnerable zones in Zambezi Region in north-eastern Namibia using remote sensing and geographic information system (GIS) techniques. A forest fire risk zone map was developed from a combination of several forest fire-promoting variables. To assess vegetation condition, Normalised Difference Vegetation Index (NDVI) was calculated from Landsat TM images resulting in six classes. A toposheet map was used to classify land cover and land use into six density categories. Using SRTM imagery elevation data and topographic map, the slope, aspect, drainage density, and other coverages were determined. Geomorphologic and meteorological data were also used in the determination of forest fire risk zones. Forest fire vulnerable zones were defined by assigning subjective weights to each layer's classes based on the perceived sensitivity to fire or ability to cause fire. The final product categorized the Zambezi Region into four fire vulnerable categories: extremely high risk, high risk, moderate risk, and low risk. An area of 137000 ha (9.6%) was at very high risk, 665400 ha (46.5%) was at high risk, and 64600 ha (4.5%) was at low risk. Vegetation structure, geomorphology, land cover, and precipitation were major determinants of fire vulnerability. High elevation and low vegetation moisture status increased fire vulnerability. Lower fire risk (than expected) was recorded at low elevations due to the vegetation type being a limiting factor. Mid-elevated areas were at very high fire risk due to interactive effects of elevation, high temperature, and low humidity. Slope, aspect, and drainage density did not significantly influence fire risk due to low occurrence of pronounced slopes and aspects.