Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying Submergence
Local scour holes are erosional bed structures that are related to different scientific disciplines in Earth science and hydraulic engineering. Local scouring at naturally placed boulders is ubiquitous, but many competing factors make it difficult to isolate the effects of a given variable. This is...
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| Format: | Article |
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MDPI AG
2023-03-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/15/5/958 |
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| author | Oliver Schlömer Jürgen Herget |
| author_facet | Oliver Schlömer Jürgen Herget |
| author_sort | Oliver Schlömer |
| collection | DOAJ |
| description | Local scour holes are erosional bed structures that are related to different scientific disciplines in Earth science and hydraulic engineering. Local scouring at naturally placed boulders is ubiquitous, but many competing factors make it difficult to isolate the effects of a given variable. This is especially true for local scouring at natural instream obstacles that are exposed to unsteady flow conditions in the course of flood hydrograph experiments. Experimental investigations in laboratory flumes offer the advantage that boundary conditions can be systematically varied. We present novel experimental data on the impact of the submergence ratio, hydrograph skewness, and flow intensity on local scouring at boulder-like obstacles during unsteady flow and evaluate the effect of discharge chronologies. In total, 48 flume experiments on subcritical clear-water conditions and channel degradation were performed. The experimental results reveal that local scouring dominantly occurred at the rising limb when flow depth was comparable to the obstacle size, so the obstacle was unsubmerged. The steeper the rising limb, the quicker the local scour hole matured. The experimental results are relevant for the hydraulic interpretation of local scour holes found at boulders in the field. They may be utilized as a proxy for the minimum duration of the beginning stage of a flood. |
| first_indexed | 2024-03-11T07:06:28Z |
| format | Article |
| id | doaj.art-501d31235463472d93c7a4e0212f0686 |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-11T07:06:28Z |
| publishDate | 2023-03-01 |
| publisher | MDPI AG |
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| spelling | doaj.art-501d31235463472d93c7a4e0212f06862023-11-17T08:55:26ZengMDPI AGWater2073-44412023-03-0115595810.3390/w15050958Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying SubmergenceOliver Schlömer0Jürgen Herget1Department of Geography, University of Bonn, 53115 Bonn, GermanyDepartment of Geography, University of Bonn, 53115 Bonn, GermanyLocal scour holes are erosional bed structures that are related to different scientific disciplines in Earth science and hydraulic engineering. Local scouring at naturally placed boulders is ubiquitous, but many competing factors make it difficult to isolate the effects of a given variable. This is especially true for local scouring at natural instream obstacles that are exposed to unsteady flow conditions in the course of flood hydrograph experiments. Experimental investigations in laboratory flumes offer the advantage that boundary conditions can be systematically varied. We present novel experimental data on the impact of the submergence ratio, hydrograph skewness, and flow intensity on local scouring at boulder-like obstacles during unsteady flow and evaluate the effect of discharge chronologies. In total, 48 flume experiments on subcritical clear-water conditions and channel degradation were performed. The experimental results reveal that local scouring dominantly occurred at the rising limb when flow depth was comparable to the obstacle size, so the obstacle was unsubmerged. The steeper the rising limb, the quicker the local scour hole matured. The experimental results are relevant for the hydraulic interpretation of local scour holes found at boulders in the field. They may be utilized as a proxy for the minimum duration of the beginning stage of a flood.https://www.mdpi.com/2073-4441/15/5/958local scour holesunsteady flowboulderflume experiments |
| spellingShingle | Oliver Schlömer Jürgen Herget Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying Submergence Water local scour holes unsteady flow boulder flume experiments |
| title | Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying Submergence |
| title_full | Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying Submergence |
| title_fullStr | Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying Submergence |
| title_full_unstemmed | Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying Submergence |
| title_short | Geometry of Local Scour Holes at Boulder-like Obstacles during Unsteady Flow Conditions and Varying Submergence |
| title_sort | geometry of local scour holes at boulder like obstacles during unsteady flow conditions and varying submergence |
| topic | local scour holes unsteady flow boulder flume experiments |
| url | https://www.mdpi.com/2073-4441/15/5/958 |
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