Preprints
https://doi.org/10.5194/esurf-2021-105
https://doi.org/10.5194/esurf-2021-105
 
21 Jan 2022
21 Jan 2022
Status: this preprint is currently under review for the journal ESurf.

Drainage reorganization induces deviations in width-area-slope scaling of valleys and channels

Elhanan Harel1, Liran Goren1, Onn Crouvi2, Hanan Ginat3, and Eitan Shelef4 Elhanan Harel et al.
  • 1Earth and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva, 84105, Israel
  • 2Geological Survey of Israel, Yesha’yahu Leibowitz 32, Jerusalem 9692100, Israel
  • 3The Dead-Sea and Arava Science Center, Tamar regional council Dead-Sea mobile post 86910, Tamar regional council, Israel
  • 4Geology and Environmental Science, University of Pittsburgh, 4107 O’Hara Street, Pittsburgh, Pennsylvania 15260-3332, United states

Abstract. The width of valleys and channels affects the hydrology, ecology, and geomorphic functionality of drainage networks. Valley and channel widths are often estimated through a power-law scaling between width (W) and drainage area (A), and where lithologic variability or differential uplift rates dominate, width was suggested to scale with both slope (S) and drainage area, through the relation W = kb Ab Sc. However, in fluvial systems that experience drainage reorganization, abrupt changes in drainage area distribution can result in widths that are disproportional to their drainage areas. Consequently, in such cases, the width-area-slope scaling is expected to deviate relative to drainages that did not experience reorganization.

To explore the effect of reorganization on width-area-slope scaling, we studied 12 valley sections in the Negev desert, Israel, categorized into undisturbed, beheaded, and reversed valleys. We found that the drainage area exponent, b, differs between valley categories, and that reversed valleys are characterized by a negative b exponent, indicating valley narrowing with increasing drainage area. A detailed study of a reversed valley reveals that unlike the negative b exponent that links drainage area to valley width, the relation between drainage area and channel width is best fitted with a positive b exponent. This difference indicates that the timescale of channel width adjustment to post-reorganization drainage area distribution is faster than that of the valley width adjustment. We find that the difference in channel width across the divide causes a step change in unit stream power between the adjusted reserved channel and the unadjusted, beheaded channel. Gradients in width and unit stream power across the divide, lead to a width-feedback that promotes ongoing divide migration and reorganization.

The identified distinct width-area-slope scaling of reorganized valleys could assist in recognizing and constraining the dynamics of landscapes influenced by drainage reorganization and likely has critical implications for the distribution of erosion rates in reorganized landscapes.

Elhanan Harel et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-105', Charles Shobe, 14 Mar 2022
  • RC2: 'Comment on esurf-2021-105', George Hilley, 15 Mar 2022
  • RC3: 'Comment on esurf-2021-105', Anonymous Referee #3, 23 Mar 2022

Elhanan Harel et al.

Data sets

Width_Area_Slope_data Elhanan Harel https://doi.org/10.5281/zenodo.5804837

Elhanan Harel et al.

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Short summary
Drainage reorganization redistributes drainage area across basins, resulting in channel and valley widths that may be unproportional to the new drainage area. We demonstrate scaling between valley width, slope and drainage area in reorganized drainages that are deviated from scaling in non-reorganized drainages. Further, deviation patterns are associated with different reorganization categories. Our findings are consequential for studies that rely on these scaling for valley width estimation.