Due to their low cost, most river embankments in Japan are Earth-mound embankments. However, Earth-mound embankments frequently burst due to heavy rains caused by typhoons and linear precipitation bands. Therefore, there is an urgent need for low-cost robust river embankments for water overflows that are more resistant to collapse. Since the most common reason for embankment failures is the infiltration of overflow water, a robust embankment with a crushed shell capillary barrier (CB) is proposed to reduce the infiltration of overflow water. To develop technologies for robust river embankments, measuring and quantifying overflow water are necessary, and the Ministry of Land, Infrastructure, Transport and Tourism of Japan (MLIT) recommended validating technologies using artificially constructed hydraulic measurement setups, referred to as pseudo embankments hereafter. In this article, as part of the development of a robust embankment with a shell CB, an overflow velocity measurement system using millimeter-wave multiple-input multiple-output (MIMO) radar is presented. A real-size pseudo embankment is fabricated, and overflow velocity measurements are conducted using this pseudo embankment. The experimental results demonstrate the effectiveness of the velocity measurement system using a millimeter-wave MIMO radar. The results show that the proposed system is capable of monitoring overflow velocities effectively over the entire pseudo embankment and has the potential to grasp the status of embankments intuitively from the reflection point clouds obtained by radar. Moreover, a comparison between the velocities measured by the proposed millimeter-wave MIMO radar system and those measured by the camera system using image processing is also provided in this article. As a result, the proposed system using a millimeter-wave MIMO radar has higher accuracy and lower computational complexity.
