Eleftherakis Dimitrios, Snellen Mirjam, Amiri-Simkooei AliReza, Simons Dick G, Siemes Kerstin
Chair Acoustics, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
Deltares, Princetonlaan 6, 3584 CB Utrecht, The Netherlands.
J Acoust Soc Am. 2014 Jun;135(6):3305-15. doi: 10.1121/1.4875236.
This contribution investigates the behavior of two important riverbed sediment classifiers, derived from multi-beam echo-sounder (MBES)-operating at 300 kHz-data, in very coarse sediment environments. These are the backscatter strength and the depth residuals. Four MBES data sets collected at different parts of rivers in the Netherlands are employed. From previous research the backscatter strength was found to increase for increasing mean grain sizes. Depth residuals, however, are often found to have lower values for coarser sediments. Investigation of the four data sets indicates that these statements are valid only for moderately coarse sediment such as sand. For very coarse sediments (e.g., coarse gravel) the backscatter strength is found to decrease and the depth residuals increase for increasing mean grain sizes. This is observed when the sediment mean grain size becomes significantly larger than the acoustic wavelength of the MBES (5 mm). Knowledge regarding this behavior is of high importance when using backscatter strength and depth residuals for sediment classification purposes as the reverse in behavior can induce ambiguity in the classification.
本文探讨了两种重要的河床沉积物分类器在极粗沉积物环境中的行为，这两种分类器源自工作频率为300kHz的多波束回声测深仪（MBES）数据，即后向散射强度和深度残差。使用了在荷兰不同河段收集的四个MBES数据集。从先前的研究中发现，随着平均粒径的增加，后向散射强度会增大。然而，对于较粗的沉积物，深度残差通常具有较低的值。对这四个数据集的研究表明，这些说法仅适用于中等粗度的沉积物，如沙子。对于极粗的沉积物（如粗砾石），随着平均粒径的增加，后向散射强度会降低，深度残差会增加。当沉积物平均粒径显著大于MBES的声波波长（5mm）时，就会观察到这种情况。当使用后向散射强度和深度残差进行沉积物分类时，了解这种行为非常重要，因为行为的反转可能会在分类中引起歧义。
