Multitemporal ALSM change detection, sediment delivery, and process mapping at an active earthflow

Abstract

Remote mapping and measurement of surface processes at high spatial resolution is among the frontiers in Earth surface process research. Remote measurements that allow meter‐scale mapping of landforms and quantification of landscape change can revolutionize the study of landscape evolution on human timescales. At Mill Gulch in northern California, USA, an active earthflow was surveyed in 2003 and 2007 by airborne laser swath mapping (ALSM), enabling meter‐scale quantification of landscape change. We calculate four‐year volumetric flux from the earthflow and compare it to long‐term catchment average erosion rates from cosmogenic radionuclide inventories from adjacent watersheds. We also present detailed maps of changing features on the earthflow, from which we can derive velocity estimates and infer dominant process. These measurements rely on proper digital elevation model (DEM) generation and a simple surface‐matching technique to align the multitemporal data in a manner that eliminates systematic error in either dataset. The mean surface elevation of the earthflow and an opposite slope that was directly influenced by the earthflow decreased 14 ± 1 mm/yr from 2003 to 2007. By making the conservative assumption that these features were the dominant contributor of sediment flux from the entire Mill Gulch drainage basin during this time interval, we calculate a minimum catchment‐averaged erosion rate of 0·30 ± 0·02 mm/yr. Analysis of beryllium‐10 (10Be) concentrations in fluvial sand from nearby Russian Gulch and the South Fork Gualala River provide catchment averaged erosion rates of 0·21 ± 0·04 and 0·23 ± 0·03 mm/yr respectively. From translated landscape features, we can infer surface velocities ranging from 0·5 m/yr in the wide upper ‘source’ portion of the flow to 5 m/yr in the narrow middle ‘transport’ portion of the flow. This study re‐affirms the importance of mass wasting processes in the sediment budgets of uplifting weak lithologies. Copyright © 2011 John Wiley & Sons, Ltd.

Digital Elevation Model Differencing and Error Estimation from Multiple Sources: A Case Study from the Meiyuan Shan Landslide in Taiwan

“…The remaining body in most cases would be moved downstream due to a subsequent heavy rainfall and, thus, the remaining rocks and the moving earthflow are threats to the downstream area. The ratio between the sediment volume flowing out of the landslide dam and the total sediment volume within the landslide dam can be defined as the sediment delivery rate [21,53,54]. This can represent degrees of erosion and sediment outflow in the water accumulation area and, thereby, provide references for hydraulic engineering or landslide disaster prevention planning.…”

“…Most of the previous comparative studies on multi-period DTM data have adopted ground control points, e.g., the discussion of landslide and river terrain variation by comparing the DTM data from ground measurements and those from aerial photogrammetry and ALS measurements [10,[17][18][19], analysis of river terrain variation and slope earthflows by contrasting between two-period [20,21] or three-period [22] ALS data and ground measurement data, evaluation of earthflow terrain variation using airborne and ground LiDAR data, and error assessment of these two techniques [23], using InSAR-derived DTM to discuss terrain changes before and after the landslide event [7], and error assessment based on the two LiDAR datasets of Taiwan [24]. All of these studies mentioned above were conducted based on accessible ground measurement points.…”

Landslide Change Detection Based on Multi-Temporal Airborne LiDAR-Derived DEMs

“…Remote sensing techniques have been used to measure surface processes by conducting change detection for volumetric change such as map erosion and deposition (e.g., [9][10][11][12]). Geomorphologic analysis for landslide terrains has consisted of field observation, airborne LiDAR, traditional surveying, global positioning system (GPS), aerial photograph interpretation, or a combination of these techniques ( [13][14][15][16][17][18][19][20]).…”

“…DoD maps have become important in landslide mapping where vertical changes reflect the spatial and temporal processes of landslides. DoD maps are highly effective means to monitor temporal changes when change calculations have accounted for measurement uncertainties [10][11][12]. In addition it is essential that DEM generation and multi-temporal registration be performed appropriately [12].…”

Geomorphological Change Detection Using an Integrated Method: A Case Study on the Taan River Watershed, Taiwan

“…The changes can then be derived from these correspondences among multi-temporal images. Meanwhile, Digital elevation model (DEM) subtraction, that is, computing the difference between two DEMs of the same site but at different times, is a common approach for assessing topographic changes (Dewitte and Demoulin 2005;Dewitte et al 2008;Corsini et al 2009;Prokop and Panholzer 2009;DeLong et al 2012;Daehne and Corsini 2013). This study proposes an integrated method combining PIV and digital surface model (DSM) subtraction.…”