Radar remote sensing of the source areas from the Coët-Dan catchment

• Published in: Hydrological processes Vol. 12; no. 2; pp. 267 - 284
• Main Authors: Gineste, Philippe, Puech, Christian, Mérot, Philippe
• Format: Journal Article
• Language: English
• Published: West Sussex John Wiley & Sons, Ltd 01.02.1998; Wiley
• Subjects: catchment scale; contributing area; Earth sciences; Earth, ocean, space; Environmental Sciences; ERS; Exact sciences and technology; Freshwater; Hydrology; Hydrology. Hydrogeology; radar remote sensing; saturation; TOPMODEL; France; Brittany; Western Europe; saturation; drainage basins; models; synthetic aperture radar; Europe; Space remote sensing; imagery; runoff; remote sensing; microwave methods; calibration; color imagery; TOPMODEL; COET DAN BASSIN VERSANT; MORBIHAN; FRANCE
• ISSN: 0885-6087; 1099-1085
• DOI: 10.1002/(SICI)1099-1085(199802)12:2<267::AID-HYP576>3.0.CO;2-G

As interest shifts to the development of models for predicting runoff quality, identification of the source areas for runoff becomes increasingly important. Active microwave remote sensing has a unique potential for surveying source areas at the catchment scale. Thresholding of the back‐scattering coefficient was initially proposed but proved unsatisfactory when applied to the ERS‐1 SAR multitemporal images acquired during winter 1992 over the Coët‐Dan catchment, concomitantly with ground observations. Difference images may, instead, allow the wettest part of the catchment to be identified provided that the two images encompass a marked hydrological event. A saturation plot could not however be obtained for each date; the use of a pair of images may be further limited by the residual speckle (although carefully filtered using the multitemporal information) and a slight inaccuracy in the SAR image calibration. It is therefore argued that considering the whole temporal back‐scatter profile would be, at present, a safer approach to the remote sensing of saturated areas. The back‐scatter temporal standard deviation appears, in this light, as a possible good indicator of the local saturation likelihood during the period of study: it is based on the fact that saturation develops on parts of the catchment that are wetter than the others through lateral recharge. Possible applications within the TOPMODEL framework are discussed. © 1998 John Wiley & Sons, Ltd.