Multi-temporal Mapping of Disturbances in the Okavango Delta, Botswana using Landsat TM and ETM+ Data

The characterization of landscape disturbance is critical for understanding ecosystem structure and function; disturbance both impacts and is impacted by spatial heterogeneity or patchiness via vegetation competition, resource availability, and even herbivory [1, 2]. The research presented here focuses on the distal portions of the Okavango Delta in northern Botswana, where both fire and flooding are prevalent on the landscape. An overarching goal of this research is determining how the interaction of these two disturbances influences the distribution of the plant types that, in turn, potentially alter ecological function. This paper examines the spatial configuration of these disturbances via remotely sensed imagery and assesses whether these patterns are discernible in a 2001 land cover classification. Annual flooding and fire histories from 1989 to 2002 (14-years) were extracted from a multi-temporal Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) time series consisting of 87 images with an average time step of approximately 2 months. These 14-year fire and flooding history maps were combined to map disturbance history (DH) clusters, defined based on the number of times a pixel burned and/or was flooded from 1989 to 2002. Similarly, disturbance return (DR) clusters, or the average return time for an event, were also defined and mapped for the 14-year cycle.