ABSTRACT: Close-range photogrammetry for high resolution modeling of river bed topography in small channels.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Close-range photogrammetric techniques offer a unique view of small, forested stream channels. In many environments, channels <20 m in bankfull width are concealed beneath a riparian tree canopy and the bed cannot be viewed with conventional, large-scale aerial photographs. Under these conditions, data collection techniques suitable for the production of a high resolution (i.e., centimeter-scale) digital elevation model (DEM) of the channel bed and banks often involve relatively labor intensive field surveys using standard field equipment (e.g., an automatic level or total station) and spatial interpolation between surveyed points. More recently, such data have been collected via relatively expensive airborne or terrestrial lidar survey. This paper presents a technique for modeling and monitoring river bed topography using close-range photogrammetry and a non-metric camera. Imagery is acquired beneath the riparian canopy and 10 m above the bed so that relatively narrow, forested channels can be imaged at close range and high resolution. A description of the camera platform is presented, the importance of DEM post-processing is illustrated, and the spatial distribution of errors in the DEM surface are discussed in relation to the morphological features of the channel and submerged areas of the bed. The technique provides cost-effective, high resolution topographic and bed roughness data for small channels that can be used to model flow characteristics and describe the spatial distribution of bed scour and fill and the volumetric change in bed material storage. The technique is best suited for channel reaches <100 to 200 m in length.

Bibliography of Canadian Geomorphology