Passive Acoustic Measurement of Bedload Transport in Natural Bedrock Channels

本提案的目的是设计和校准一种非侵入性的被动声学系统，用于测量天然基岩河道中的空间综合推移质输移率。我们提出了测量推移质碎石在运输过程中的自生噪声的方法。我们的实验设计包括沿100米范围部署的8个水听器和8个检波器，数据经过笔记本电脑上的16通道模数转换板后记录到磁盘上。手机将被涂在基岩上、靠近河岸的地方，以及溪流中心的大石头上。将对水听器阵列和地震检波器阵列进行比较，以确定哪一个更可取，并消除来自流体湍流、空化和气泡坍塌的信号。宽带和窄带幅度都将被分析，以预测推移质输运的能力。顺流阵列的目的是利用推移质输运的下行传播波的存在，并确定最优的抽样设计。该系统将使用常规技术(如鹰丝网捕集器和Helley-Smith采样器)在低流量时观测到的推移质输沙率进行校准，在高流量时通过对河流流入死水的三角洲进行多次调查来进行校准。三角洲调查将使用浅水回声探测仪完成。关键水力变量也将在研究河段进行测量，以便将这些变量与测量的推移质通量联系起来。其结果将是一种在很短的时间间隔内测量基岩河段横断面综合推移质输沙率的非侵入性方法。

0126131SlingerlandThe objective of this proposal is to design and calibrate a non-invasive, passive acoustic system for measuring spatially-integrated bedload transport rates in a natural bedrock channel. We pro-pose to measure the self-generated noise of bedload clasts in transport. Our experimental design consists of eight hydrophones and eight geophone deployed along a 100m reach, with data recorded to disk after passing through a sixteen-channel analog-to-digital conversion board on a laptop computer. The phones will be epoxied onto bedrock, near the banks, and onto large boulders in the center of the stream. The hydrophone array and the geophone array will be compared to determine which, if either, is preferable and to eliminate signals from fluid turbulence, cavitation, and bubble collapse. Both broadband and narrowband amplitudes will be analyzed for predictive power of bedload transport. The purpose of the streamwise array is to exploit the presence of downstream propagating waves of bedload transport and to determine an optimal sampling design. The system will be calibrated using bedload transport rates observed at low flows by conventional techniques such as chickenwire traps and Helley-Smith samplers, and at high flows by multiple surveys of a delta where the stream empties into a standing body of water The delta surveys will be accomplished using a shallow-water echosounder. Key hydraulic variables also will be measured in the study reach in order to relate these variables to measured bedload fluxes. The result will be a non-invasive method for measuring cross-sectionally-integrated bedload transport rates in bedrock reaches at very short time intervals.