Study on field measurement of sand waves in a natural river

由于缺乏测量仪器，天然河流洪水期间沙波的现场测量很少。因此，本研究的目的是开发一套无需人工操作的天然河流沙波现场测量系统。该系统采用带有回声测深仪的遥控船和全站仪对船的位置进行测量。为了开发这一系统，有必要对测量数据进行积累和验证。第一年，我们研制了遥控船，并在仙台河进行了枯水流量的现场测量。结果表明，该系统可以在低流速时以足够的精度测量天然河流的河床水位，并在接下来的一年中对遥控船进行了改装，以便在洪水等高流速时进行测量，并对上述时间段的测量精度进行了评估。对该系统在恶劣天气条件下监测中出现的几个问题进行了研究，并从实际测量出发，研究了沙粒直径、床面坡度等河床条件对监测结果的影响，以及降噪方法。最后，完成了一个完整的现场测量系统。然而，很遗憾，我们未能在洪水期间获得测量结果。因为今年没有发生大的洪涝灾害，所以我们不能掩盖所有应用测量系统的情况。

There have been few field measurement of sand waves in a natural river during flood, due to lack of the measuring instrument. Therefore, the purpose of this study is to develop a filed measuring system for sand waves in natural rivers without man's operation. In this system, remote control boat with echo-sounder and total station which measures the position of boat are used. In order to develop this system, it is necessary to accumulate the measurements and verify their accuracy.During the first year, we had developed the remote control boat and taken the filed measurement in Sendai River during low water discharge. It is found that the bed level in a natural river can be measured with sufficient accuracy in this system during low velocity.In the following year, we have modified the remote control boat in order to conduct the measuring during high velocity such as flood and evaluated the accuracy of the measurement over the above period. Several problems in monitoring which occurred in this system during bad wether condition were investigated.This year as the last year of investigation, the influence of bed conditions such as sand diameter and bed slope, and noise reduction method from actual measurement have been studied. Finally, a total field meauring system was completed. However, we regret that we were not able to obtain the measurement during flood. Because there were no major flood this year so that we could not cover up all cases for application of measuring system.