Remote monitoring of regional inundation patterns and hydroperiod in the Greater Everglades using Synthetic Aperture Radar

Abstract

Understanding the hydrologic patterns in vast wetland ecosystems has proven to be a difficult task. Most of the world’s wetland ecosystems are not adequately monitored for water level, flow, or discharge, and where these are monitored, gauges are usually located on the largest rivers or lakes and canals rather than in the seasonally flooded areas. Even those wetlands that have the most extensive networks of gauges are not sufficiently covered to understand the finer-scale spatial dynamics of hydrologic condition. However, high-density in situ monitoring of stage, flow, and discharge of vast wetland complexes would be prohibitively expensive, even in a region such as south Florida, USA where considerable resources are devoted to water management. Several techniques are presented that were developed to use Synthetic Aperture Radar (SAR) satellite imagery to remotely detect, monitor, and map regional scale spatial and temporal changes in wetland hydrology. This study shows that SAR imagery can be used to create inundation maps of relative soil moisture and flooding in non-woody wetlands. A comparison of in situ water-level data collected from 1997 to 1999 at 12 test sites to SAR imagery revealed that relative backscatter within a site does vary in a linear fashion with changes in water levels. Using SAR imagery collected between 1997 and 1999, inundation maps were created at approximately bi-monthly periods for the south Florida region. This time series of inundation/soil moisture maps (1997–1999) reveals the spatial and temporal variation in degree of flooding in the Greater Everglades, which is information previously unavailable from ground-based observations alone. In addition, hydroperiod maps were created based on a temporal series of 14 months of SAR imagery.