Mapping gravel bed river bathymetry from space

Abstract

[1] Understanding river form and behavior requires an efficient means of measuring channel morphology. This study evaluated the potential to map the bathymetry of two clear-flowing, shallow (<3 m deep) gravel bed rivers <60 m wide from 2 m-pixel WorldView2 satellite images. Direct measurements of water column optical properties were used to quantify constraints on depth retrieval. The smallest detectable change in depth was 0.01-0.04 m and the maximum detectable depth was 5 m in green bands but <2 m in the near-infrared; lower sensor radiometric resolution yields less precise estimates over a smaller range. An algorithm for calibrating a band ratio X to field measurements of depth d proved effective when applied to spectra extracted from images (R 2 = 0.822 and 0.594 for the larger and smaller stream, respectively) or measured in the field (R 2 = 0.769 and 0.452). This procedure also identified optimal wavelength combinations, but different bands were selected for each site. Accuracy assessment of bathymetric maps produced using various calibration approaches and image types indicated that: 1) a linear d vs. X relation provided depth estimates nearly as accurate as a quadratic formulation; 2) panchromatic and pan-sharpened multispectral images with smaller 0.5 m pixels did not yield more reliable depth estimates than the original images; and 3) depth retrieval was less reliable in pools due to saturation of the radiance signal. This investigation thus demonstrated the feasibility, as well as the limitations, of measuring the bathymetry of clear, shallow gravel bed rivers from space.

Technical note: Bathymetry observations of inland water bodies using a tethered single-beam sonar controlled by an unmanned aerial vehicle

“…The full potential of UAV-borne hydrological observations will be exploited only with flight operations beyond visual line of sight. The new generation of waterproof rotary wing UAVs equipped with visual navigation sensors and automatic ≈ 2 m; 1-1.5 m 0.10-0.20 m ≈ 1-1.5 times the Secchi depth Fonstad and Marcus (2005), Legleiter and Overstreet (2012). Bailly et al (2012Bailly et al ( , 2010, Charlton et al (2003), Hilldale and Raff (2008), Kinzel et al (2007).…”

Seamless Mapping of River Channels at High Resolution Using Mobile LiDAR and UAV-Photography

“…River researchers employing photography based bathymetry modelling have mostly focused on aerial photography, because the higher spatial resolution that can be achieved this way suits the scale of analysis better than coarser satellite data. However, high resolution satellite data has recently also been used to map gravel bed rivers in Wyoming, USA [48].…”

Mapping the bathymetry of supraglacial lakes and streams on the Greenland ice sheet using field measurements and high-resolution satellite images

“…This study addressed these shortcomings by applying spectrally based depth retrieval methods developed in shallow marine settings (e.g., Dierssen et al, 2003) and adapted to alluvial rivers (e.g., Legleiter and Overstreet, 2012) to the GrIS. More specifically, we evaluated the performance of a band ratio-based algorithm expected to be robust to variations in bottom albedo and water column optical properties (Stumpf et al, 2003;Legleiter et al, 2009).…”