Monitoring wetland ditch water levels in the North Kent Marshes, UK, usingLandsat TM imagery and ground-based measurements

Am understanding of hydrology is a prerequisite for ensuring the successful management, conservation and restoration of wetland environments. Frequent ly, however, little is known about historical hydrological conditions, such as water levels, within wetlands. Moreover, many channel and ditch systems in wetlands arc not routinely monitored, except perhaps for research purpo ses. A methodology is presented herein which makes use of satellite imagery to indirectly provide remotely sensed observations of water levels within channels and ditches. Using multi-temporal Landsat Thematic Mapper (TM) ima gery and simultaneous ground-based measurements of water levels, statistica l relationships are established between satellite-derived effective wet dit ch widths and measured water levels in the drainage system of the Elmley Ma rshes, southeast England. These relationships can be used subsequently to e stimate historical ditch water levels and to monitor contemporary ditch wat er levels in the wetland. The study shows that satellite imagery has much t o offer in monitoring changes in the hydrological regime of wetlands and in providing complimentary approaches to field monitoring.