536 Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001. Summer flood mapping in a northern wetland using a combination of Radarsat and SPOT imagery JESSIKA TÔYRÂ Department of Geography, University of Saskatchewan, 9 Campus Drive, Saskatoon, Saskatchewan S7N 5A5, Canada e-mai I : iessika.tovra@ec.gc.ca ALAIN PIETRONIRO National Water Research Institute, 11 Innovation Boulevard, Saskatoon, Saskatchewan S7N 3H5, Canada LAWRENCE W. MARTZ Department of Geography, University of Saskatchewan, 9 Campus Drive, Saskatoon, Saskatchewan S7N 5A 5, Canada Abstract This paper evaluates the use of Radarsat and SPOT imagery for mapping the extent of standing water in the Peace-Athabasca delta (Canada) wetland complex during the summer of 1998. It is hypothesized that since Radarsat and SPOT images contain complementary information, flood mapping would be more efficient when the two image types are used in combination. A Radarsat scene, a SPOT scene, and a combination of the two were classified using the Mahalanobis distance algorithm. The results indicate that wetland flood mapping in summer conditions is feasible with about 80% accuracy when a combination of Radarsat and SPOT imagery is used. Key words classification; flood mapping; multi-sensor; Peace-Athabasca delta (Canada); Radarsat; SPOT; wetland INTRODUCTION Remoteness and difficult access require the use of remote sensing for most mapping activities in the Peace-Athabasca delta (Canada; 58°40'N, 111°15'W). Radarsat imagery is useful for flood mapping as the radar pulses penetrate vegetation to some degree and provide information about the geometric and dielectric characteristics of the objects. While the visible and infrared wavelengths recorded by the SPOT multispectral sensor cannot penetrate dense vegetation, they contain information about the spectral differences between upland and wetland vegetation. It has been shown that a combination of Radarsat and SPOT improves the accuracy of wetland flood mapping in spring conditions (Tôyrâ et al, 2000). This study evaluates the use of Radarsat and SPOT data for delineating standing water in the Peace-Athabasca delta during the summer of 1998 when the trees were fully foliated. METHODOLOGY Radarsat SI and SPOT multispectral scenes were obtained for 21 and 26 July 1998, respectively. The Radarsat scene was calibrated to derive radar backscatter values (Srivastava, 1997) and filtered with the Kuan adaptive filter (Kuan et al, 1987) to