Estimation of erosion and deposition volumes in a large, gravel‐bed, braided river using synoptic remote sensing

Abstract

System-scale detection of erosion and deposition is crucial in order to assess the transferability of findings from scaled laboratory and small field studies to larger spatial scales. Increasingly, synoptic remote sensing has the potential to provide the necessary data. In this paper, we develop a methodology for channel change detection, coupled to the use of synoptic remote sensing, for erosion and deposition estimation, and apply it to a wide, braided, gravel-bed river. This is based upon construction of digital elevation models (DEMs) using digital photogrammetry, laser altimetry and image processing. DEMs of difference were constructed by subtracting DEM pairs, and a method for propagating error into the DEMs of difference was used under the assumption that each elevation in each surface contains error that is random, independent and Gaussian. Data were acquired for the braided Waimakariri River, South Island, New Zealand. The DEMs had a 1Ð0 m pixel resolution and covered an area of riverbed that is more than 1 km wide and 3Ð3 km long. Application of the method showed the need to use survey-specific estimates of point precision, as project design and manufacturer estimates of precision overestimate a priori point quality. This finding aside, the analysis showed that even after propagation of error it was possible to obtain high quality DEMs of difference for process estimation, over a spatial scale that has not previously been achieved. In particular, there was no difference in the ability to detect erosion and deposition. The estimates of volumes of change, despite being downgraded as compared with traditional cross-section survey in terms of point precision, produced more reliable erosion and deposition estimates as a result of the large improvement in spatial density that synoptic methods provide.

Integrating ecology with hydromorphology: a priority for river science and management

“…channel form or invertebrate assemblages) can provide detailed information about process rates. Fluvial geomorphology provides good examples, such as quantifying sediment transport rates using temporal series of channel form records (Fuller et al, 2002;Lane et al, 2003). However, the financial and logistical demands of research spanning many years frequently restricts opportunities, despite widespread recognition of the value of research carried out over large spatial and/or temporal extents, such as the Long Term Ecological Research Network (Symstad et al, 2003).…”

Effects of channel morphology and sensor spatial resolution on image-derived depth estimates

“…41 When multi-temporal image data are available, the synoptic 42 perspective offered by aerial platforms has allowed geo-43 morphologists to document channel changes associated with 44 flood events (Bryant & Gilvear, 1999) and estimate volumes 45 of erosion and deposition in large, braided river systems 46 (Lane et al, 2003). Recent increases in the number and…”

Rainfall simulation and Structure-from-Motion photogrammetry for the analysis of soil water erosion in Mediterranean vineyards

“…The DoDs are referred to in the text as DoDs NKN and DoDs PHO for those derived from the Nikon and smartphone cameras, respectively. DEMs' uncertainty in DoDs has also been considered (Brasington et al, 2000;Lane et al, 1994;Lane, 1998;Lane et al, 2003;Prosdocimi et al, 2015;Wheaton, 2008;Wheaton et al, 2010). In this case, DEMs' uncertainties were evaluated according to a probabilistic thresholding that can be carried out with a user-defined confidence interval (Brasington et al, 2003;Lane et al, 2003;Taylor, 1997):…”