Modeling of spatiotemporal variations in runoff contribution areas and analysis of hydrologic connectivity

Abstract

Traditional delineation and modeling methods do not consider the spatial arrangement and dynamic threshold control of surface depressions. Instead, full structural hydrologic connectivity, uniform well‐connected drainage networks, and an invariant contributing area are often assumed. In reality, depressions play an important role in quantifying functional connected areas (ACs) and contributing area. This study is aimed to develop a new procedure to analyze functional hydrologic connectivity related to topography at a mesoscale, specifically in depression‐dominated areas by (a) characterizing surface topography, (b) quantifying and locating dynamic hydrologic connectivity, and (c) analyzing hydrologic connectivity and threshold‐controlled dynamics of contributing area using a set of dimensionless indicators and a new normalized connected area function. Thorough analyses for different topographic surfaces provided improved understanding of the intrinsic relationship and interaction between structural and functional hydrologic connectivity patterns. In addition, the new procedure was compared against a traditional delineation method, terrain analysis using digital elevation models (TauDEM), to determine structural and functional connectivity. It was found that spatial arrangement and scale of depressions had a direct effect on hydrologic connectivity. A stepwise trend, unique to depression‐dominated areas, highlighted the effect of threshold behaviors on contributing area and ACs. Conversely, dendritic surfaces showed an expedited surface connectivity due to the assumption of depressionless topography. Thus, precisely locating and quantifying ACs and contributing area via the new analysis procedure improve our understanding of the mechanisms of topography‐controlled overland flow and sediment transport dynamics, and hence, the findings are valuable in making informed decisions about water quantity and quality across varying topographic surfaces.

The effects of topographic depressions on multiscale overland flow connectivity: A high‐resolution spatiotemporal pattern analysis approach based on connectivity statistics

“…, where τ(h) represents the probability that any pair of cells separated by a given lag distance h is connected. Note that the lag is similar to the connectivity threshold behaviour indicated in the hydrograph analysis from plot and field studies (e.g., Grimm & Chu, 2018 and (b) the depression-filled digital elevation model (DEM Fill ) for a "V"-shaped depression, which is located in the riparian zone by the main stream. Depression filling method used in this study is based on Planchon and Darboux (2002).…”

“…Each segment of ∆τ ( h ) should represent distinctive spatiotemporal characteristics of overland flow connectivity changes, for example, magnitudes and directions, caused by depressions. The concept of segmentation is similar to the connectivity threshold behaviour indicated in the hydrograph analysis from plot and field studies (e.g., Grimm & Chu, ). However, the streamflow hydrograph at a watershed outlet does not typically show the boundaries (connectivity thresholds) of these segments, such as stepwise changes of connectivity.…”

“…Connected overland flow distance or “connectivity length” has been estimated using a water “walker” conditional function on random crater‐like and low‐relief DEMs from the most upslope location to the field outlet (Darboux et al, ). Threshold behaviours of connectivity have been found and related to the spatial configurations of microtopographic depressions and their storage changes during water filling, merging, spilling, and splitting (Antoine et al, ; Grimm & Chu, ; Tromp‐van Meerveld & McDonnell, ).…”

A New Algorithm for Delineation of Surface Depressions and Channels

“…Consequently, the MPA obtained by HUD-DC is larger than that from Arc Hydro. The delineation results of both methods highlight the importance of depressions in watershed modeling for depression-dominated areas [18][19][20].…”

“…In reality, depressions have threshold controls on the hydrologic connectivity of a watershed [15][16][17], and only a portion of the watershed contributes surface runoff to the outlet in most rainfall-runoff events. In recent years, various studies, which focused on investigating hydrologic connectivity and the related impacts on hydrologic processes, highlighted the significance of depressions [18][19][20]. Therefore, approaches are used in HUD-DC for watershed-scale surface delineation.…”