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Title: USING C-BAND SYNTHETIC APERTURE RADAR DATA TO MONITOR FORESTED WETLAND HYDROLOGY IN MARYLAND'S COASTAL PLAIN.

Author
item Lang, Megan
item KASISCHKE, E - UNIVERSITY OF MARYLAND

Submitted to: IEEE Transactions on Geoscience and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2007
Publication Date: 1/1/2008
Citation: Lang, M.W., Kasischke, E.S. 2008. Using C-band synthetic aperture radar data to monitor forested Wetland Hydrology in Maryland's Coastal Plain. IEEE Transactions on Geoscience and Remote Sensing. 46(2):535-546.

Interpretive Summary: Wetland hydrology (flooding and soil moisture) is the dominant control on wetland function and extent, but scientists predict that it will be altered due to climate change and human impact. Unfortunately, broad-scale forested wetland hydrology is difficult to monitor with ground and aerial photography based methods. Satellite-borne C-band (6 cm wavelength) synthetic aperture radar data have the potential to improve the capability to monitor forested wetland hydrology, but the abilities and limitations of these data need to be fully explored. In this study, we examined the ability of multiple types of C-band data to monitor levels of flooding and soil moisture throughout the year in a typical Mid-Atlantic floodplain and the limitations inherent to C-band data (data type and forest characteristics). The relationship between backscatter (percent of emitted energy returned to the sensor) and flooding, soil moisture, tree density, tree height, and leaf density was examined. Significant differences in backscatter were found between forested areas of varying hydrology (0-60% area inundated) throughout the year. Based on our findings, we concluded that C-band data should be able to monitor hydrology beneath forest canopies throughout the year. Our findings support previous studies that concluded that C-band imagery could be used to monitor forested wetland hydrology, but our study investigated the abilities of different types of data year-round and was conducted with direct measurements of flooding and soil moisture, in a much smaller floodplain system with lower levels of flooding (< 60%).

Technical Abstract: Wetland hydrology (inundation and soil moisture) is the dominant control on wetland function and extent, but scientists predict that it will be altered due to climate change and anthropogenic impact. Unfortunately, broad-scale forested wetland hydrology is difficult to monitor with ground-based and optical remote sensing methods. C-band synthetic aperture radar data have the potential to improve the capability to monitor forested wetland hydrology, but the abilities and limitations of these data need to be fully explored. In this study, we examined the ability of ENVISAT ASAR (C-HH and C-VV) data to monitor different levels of inundation and soil moisture throughout the year in a typical Mid-Atlantic floodplain and the limitations inherent to C-band data (polarization and plant phenology) in this environment. The relationship between backscatter coefficient and inundation, soil moisture, basal area, tree height, and canopy closure was examined. Significant differences in C-HH backscatter coefficient were found between forested areas of varying hydrology (0-60% area inundated) throughout the year and C-VV backscatter coefficient during the leaf-off season. As expected, C-HH SAR backscatter was better correlated with inundation and soil moisture that C-VV SAR backscatter, and the correlations between both polarizations of backscatter and hydrology were stronger during the leaf-off season (C-HH leaf-off r2 = 0.50, leaf-on r2 = 0.39; C-VV leaf-off r2 = 0.21, leaf-on r2 = 0.19; all significant at p< 0.0001 level). Based on our findings, we concluded that C-HH data should be able to monitor hydrology beneath forest canopies throughout the year, and C-VV data should be able to do so during the leaf-off season. Our findings support previous studies that concluded that C-band imagery could be used to monitor forested wetland hydrology, but our study investigated the abilities of C-HH and C-VV data year-round and was conducted with direct measurements of inundation and soil moisture, in a much smaller floodplain system with lower levels of inundation (<60%).