Gravel bed channels of single-thread ephemeral streams in drylands are typified by alternations of steep, coarse-grained bars and less steep, fine-grained ‘flats’. The origin of both macroforms has been discussed but not fully explained. We studied the generation of this macroform sequence under field conditions. Relevantly, we provide a possible explanation regarding their formation, using a simple mathematical model fed by data obtained from field experiments carried out on the Yatir channel in the northern Negev, Israel. The mathematical model is developed considering the one-dimensional model of flow over an erodible bed composed of a bimodal mixture of sediments. The solution is obtained via the application of linear stability analysis. Results suggest that the bar-flat pattern occurs when the standard deviation of the sediment mixture is relatively large, as in the case of the Yatir channel, and the flow approaches critical conditions for bedload transport.
Formation of Repeating Bedforms (Bars-Flats) in Ephemeral Channels: From Field Observations to Modeling / Massera, G.; Siviglia, A.; Tubino, M.; Cohen, T.; Laronne, J. B.; Dorman, M.; Reid, I.; Powell, D. M.. - (2024), pp. 277-281. ( 11th International Conference on Fluvial Hydraulics, River Flow 2022 Kingston - Ottawa 2022) [10.1201/9781003323037-38].
Formation of Repeating Bedforms (Bars-Flats) in Ephemeral Channels: From Field Observations to Modeling
Massera G.;Siviglia A.;Tubino M.;
2024-01-01
Abstract
Gravel bed channels of single-thread ephemeral streams in drylands are typified by alternations of steep, coarse-grained bars and less steep, fine-grained ‘flats’. The origin of both macroforms has been discussed but not fully explained. We studied the generation of this macroform sequence under field conditions. Relevantly, we provide a possible explanation regarding their formation, using a simple mathematical model fed by data obtained from field experiments carried out on the Yatir channel in the northern Negev, Israel. The mathematical model is developed considering the one-dimensional model of flow over an erodible bed composed of a bimodal mixture of sediments. The solution is obtained via the application of linear stability analysis. Results suggest that the bar-flat pattern occurs when the standard deviation of the sediment mixture is relatively large, as in the case of the Yatir channel, and the flow approaches critical conditions for bedload transport.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione
