Influence of flood events on the response of steep and coarse-grained channels to base-level lowering in an arid setting

Nadav Broner, Jonathan B. Laronne, Yael Storz-Peretz

Research output: Contribution to journalArticlepeer-review

Abstract

The Dead Sea level has been undergoing a continuous and rapid lowering, presently ∼ 1.1 m/yr, providing a real time laboratory to examine the response of drainage systems to base level drop. There is a gap of knowledge concerning the impact of floods on the fluvial system in an environment of continuous base level lowering. Such knowledge is of pronounced importance due to the world-wide reduction of natural water recourses caused by human and climate impacts. We relate the effects of flash floods on morphological changes in small, steep and coarse-grained alluvial channels as a response to a rapid base level fall. We studied the steep (7–9 %) David and Qedem channels draining to the Dead Sea by (i) monitoring flow events using depth transducers and (ii) topographic changes by repeat drone-based photogrammetric surveys to quantify fluvio-morphological dynamics, and (iii) analyzed boulder-related bedforms and their distance from the thalweg. Altogether 15 monitored flow events of varying magnitude led to a wide range of fluvio-morphological changes. Considerable erosion occurred as expressed by bank collapse and channel bed incision. Small events displayed incision with morphological changes limited to the downstream reach, while larger events caused morphological changes throughout the entire channel. Substantial deposition at the outlet occurred together with local mechanisms of deposition upstream. The extents of erosion and net volumes of change highly correlated with event peak-discharge and event water volume. Frequent thalweg deflections occurred, some of which were related to the interaction with boulders. Boulder ribs displayed processes of formation/destruction in multiple phases, often occurring in larger events. The examined aspects illustrate the unique dynamics of a continuously unstable fluvial system under a flash-flood hydrological regime and its impact on fan delta incision and sediment transport processes.

Original languageEnglish
Article number132075
JournalJournal of Hydrology
Volume645
DOIs
StatePublished - 1 Dec 2024

ASJC Scopus subject areas

  • Water Science and Technology

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