| Autor: |
Ebrahimi, Masoumeh, van Damme, Myron, van Hemert, Henk, Soares-Frazão, Sandra |
| Předmět: |
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| Zdroj: |
Journal of Hydraulic Engineering; Jan2025, Vol. 151 Issue 1, p1-18, 18p |
| Abstrakt: |
Coastal and riverine levees are prone to wave and steady-flow overtopping, which can result in breaching and consequential flooding of the hinterland. Full-scale field experiments on a levee are a sound approach to understanding of the underlying physical processes without suffering from scale effects, provided that accurate and valuable data can be collected. This paper outlines how close-range photogrammetry was applied to monitor a levee's morphological evolution continuously and intermittently during wave overtopping. High-resolution spatial topographical models were obtained from which erosion rates could be quantified. Two camera setups—a system of multiple stationary synchronized cameras and a single mobile camera—were used for photo acquisition. The first configuration enabled reconstruction of the target zone as a dynamic scene and reduced photogrammetric analysis time through simultaneous processing of several frames [four-dimensional (4D) processing]. The second configuration applied the structure-from-motion (SfM) technique using multiple overlapping photographs to obtain three-dimensional (3D) elevation models at specific moments. Both approaches resulted in high-resolution digital elevation models (DEMs) with low mean absolute errors (MAEs) on the order of a few centimeters. Furthermore, photogrammetry proved to be highly flexible and could be applied to different types of levees with various cover layers, hydraulic loads, and meteorological conditions. Practical Applications: Monitoring erosion due to wave overtopping of levees was achieved here using close-range photogrammetry in two series of field experiments with distinct camera setups. The experiments were conducted at 1∶1 scale at the Living Lab Hedwige Prosperpolder to study the erosion processes of the levee's clay's protection layer (1-m-thick clay) on the landward-side slope subjected to loads by overtopping waves. The experiments were conducted on a levee cover in (1) its natural state; and (2) after treating clay with lime for reinforcement. In the first series of experiments, a system of 10 synchronized stationary cameras was used to capture photos. To focus on the erodibility of the natural clay cover, the 0.2-m-thick grass cover was removed over an area of 14 m2 at three locations on the slope prior to testing. In the second series, a single camera was moved around the scene at specific time intervals. An object featuring a building was also embedded in each new slope revetment to evaluate the effects on erosion of flow around obstacles. Both generated accurate erosion maps, with a slightly higher accuracy and ease of post-treatment for the multiple-camera setup. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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