How pixel size affects a sediment connectivity index in central Belgium. Issue 4 (27th December 2017)

• Record Type: Journal Article
• Authors: Cantreul, Vincent; Bielders, Charles; Calsamiglia, Aleix; Degré, Aurore
• Is Part Of: Earth surface processes and landforms. Volume 43:Issue 4(2018)
• Page Start: 884
• Page End: 893
• Publication Date: 2017-12-27
• Subjects: sediment connectivity -- index -- DEM -- pixel size -- agricultural watershed; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.4295
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Connectivity has become an increasingly used concept in hydrological and sediment research. In order to quantify it, various indices have been proposed since the start of the 21st century including the index of connectivity. This index is based on a limited number of factors, the most important one being topography. Sediment connectivity indices values probably depend on the digital elevation model (DEM) resolution. The aim of this study was, first, to compare the effect of DEM pixel size (between 0.25 and 10 m, using an UAV) in the Belgian loess belt, a lowland area. We show that the index values were lower when the pixel size decreased (a difference of about 20% in value between 0.25 and 10 m). In addition, the impact of linear features in the watershed (e.g. grass strip, bank and road) was lower with the largest pixel sizes, and the connectivity pattern was affected with a pixel size of 5 m or more. At lower pixel sizes (1 m or below), some more disconnected regions appeared. These corresponded with zones where there had been water stagnation during and after rainfalls, and was corroborated by field observations. This confirmed the need for a proper resolution according to the objectives of the study. The second aim of this study was to deduce a minimum pixel size for connectivity study, helping local erosion or sedimentation location and consequent land management decisions. In our context, 1 m stands as the optimum DEM resolution. This pixel size permitted location of all 'key areas' in terms of erosion. Very high resolutions (<0.5 m) did not generate much more information, and their calculation time was far greater. Copyright © 2017 John Wiley & Sons, Ltd. Abstract : 1 m stands as the optimal resolution to study hydrological and sediment connectivity in loamy Belgian context with gentle slopes. Field observations allowed validation of index of connectivity values which identified all "key areas" in the watershed.