Surrounding the Colorado River Delta is the Sonoran sand sea to the east, delta deposits to the north, and basin and range country plus tidal salt flats to the west. Eolian sands at the western end of the sand sea form a 100-m high escarpment between the Sonoran desert–plateau and the Gulf of California. The western edge of the sand sea has a narrow zone of badland topography with well-developed dendritic drainage patterns. Where the sand sea meets the Gulf of Mexico, eolian sands predominate along the strand. Geometry of the spits indicates a net northward transport of eolian sands into the channel and shoal architecture of the delta. An array of longshore mudflats, salt flats, spits, bars, and coastal dunes dominate the shores of the Gulf.

The USGS EROS data center provided standard images on CD-ROM to order. Browse images and metadata sets are easily accessible via the Internet. Included are the latest Landsat 7 thematic mapper (ETM ) images exploiting the multispectral and panchromatic imagery of this new sensor. The image size of Lansat ∼ 185 × 185 is particularly valuable in study of deltas because most will fit in a single frame. The revisit time interval of 15 d, however, falls way short of what is needed in coastal waters.