In the process of rapid planning and development of modern cities, underground infrastructure is often ignored because of its occultity. For this reason, whenever the rainy season comes, some streets and urban areas often have serious water accumulation, and internal disasters cause inconvenience to people's daily life and travel, and even cause public safety accidents. In order to strengthen the monitoring of urban roads and possible safety accidents during the rainy season or heavy rainfall, liquid level sensors can be used to detect the accumulation of water at a specific depth to respond to the regulatory authorities and to issue warning information to the public.
The liquid level sensor uses optical principle to detect whether the water level reaches a certain height and can be used to reflect the liquid level, pressure and weight. In the urban road water monitoring, the liquid level sensor is installed at the set warning height, especially for some low-lying or culverts. When the accumulated water reaches the warning height, the sensor changes its refractive index at the interface due to contact with water (relatively when it is not in contact with water), so that the received light inside the sensor changes and the presence or absence of the liquid is detected. Since the level sensor can only detect the water level at a certain height and cannot change the water level, it is possible to perform more accurate detection by deploying multiple sensors at different heights, reflecting different levels of water accumulation and changes.