Changes in stream power and morphological adjustments at the event-scale and high spatial resolution along an ephemeral gravel-bed channel

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Title: Changes in stream power and morphological adjustments at the event-scale and high spatial resolution along an ephemeral gravel-bed channel
Authors: Conesa García, Carmelo | Puig-Mengual, Carlos | Riquelme, Adrián | Tomás, Roberto | Martínez Capel, Francisco | García-Lorenzo, Rafael | Pastor Navarro, José Luis | Pérez-Cutillas, Pedro | Martínez Salvador, Alberto | Cano, Miguel
Research Group/s: Ingeniería del Terreno y sus Estructuras (InTerEs)
Center, Department or Service: Universidad de Alicante. Departamento de Ingeniería Civil
Keywords: Stream power | Morphological sediment budget | Bedforms | SfM photogrammetry | Terrestrial laser scanning | Gravel-bed ephemeral channel | Southeastern Spain
Knowledge Area: Ingeniería del Terreno
Issue Date: 26-Nov-2021
Publisher: Elsevier
Citation: Geomorphology. 2022, 398: 108053. https://doi.org/10.1016/j.geomorph.2021.108053
Abstract: Sediment budgets and morphological channel adjustments are closely related to changes in stream power. In ephemeral channels, whose geomorphic response depends on the magnitude and frequency of hydrological events isolated in time, such relationships are often difficult to establish. This study sought to quantitatively relate morphological adjustments to stream power along different reference channel reaches for the period 2018–2020 in the Azohía Rambla, a Mediterranean gravel-bed ephemeral stream in southeastern Spain. Very high resolution digital terrain models (VHR DTM) (at 1 to 2.5 cm pixel size), combined with ortophotographs and 3D point clouds, generated via SfM photogrammetry and terrestrial laser scanning (TLS) for pre- and post-event stages, together with ground-based surveys were used to estimate the spatial variability of morphological sediment budgets and to assess channel bed mobility and changes in net sediment flux during the study period in two spatial scenarios: reference channel reaches (RCRs) and pilot bed survey areas (PBSAs). The hydraulic variables (flow velocity, Froude number, shear stress, mean stream power and energy gradient, among other) were estimated using a 1D hydrodynamic model calibrated with field information. The high resolution maps allowed a spatially-explicit analysis of stream power and transport efficiency in accordance with the areas of erosion and deposition in each RCR. The incision and bed armoring processes showed different trends according to the stream power (ω), cumulative excess energy (εc), and relative bed stability (RBS). The greatest morphological adjustments at the event scale coincided with ω values above 300 W m−2, εc higher than 3 MJ, and RBS below 0.5. The relationships between the mean stream power gradient at peak flood discharges and the changes in bed elevation verified the bed aggradation (an average surface raising of 0.17 to 0.22 m for δω/δs of −6.2 to −14.5 W m−2 m−1) during the major flood and bed scour (average surface lowering of 0.16 to 0.19 m for δω/δs of 5.8to 10.6 W m−2 m−1) in the moderated events at the bankfull and sub-bankfull stages. Furthermore, this study contributes new relevant data to the scarce existing literature on the relationships between stream power and morphosedimentary adjustments in a fluvial system highly sensitive and resilient to climate change, as is the case of ephemeral gravel-bed channels.
Sponsor: This work has been financed by ERDF/Spanish Ministry of Science, Innovation and Universities - State Research Agency (AEI)/Project CGL2017-84625-C2-1-R (CCAMICEM); State Program for Research, Development and Innovation focused on the Challenges of Society, and by the University of Alicante (Project GRE18-15).
URI: http://hdl.handle.net/10045/119880
ISSN: 0169-555X (Print) | 1872-695X (Online)
DOI: 10.1016/j.geomorph.2021.108053
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2021 Published by Elsevier B.V.
Peer Review: si
Publisher version: https://doi.org/10.1016/j.geomorph.2021.108053
Appears in Collections:INV - INTERES - Artículos de Revistas

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