Flood alarm

A stream flows near my house which, when it rains very heavily, can overflow. Two years ago my house was flooded with 70 cm of water and I had to do a lot of renovation work on the house and replace a lot of water damaged furniture. My car was also severely damaged. Last winter I had damage even if of minor entity (5 cm of water).

I want to make a project that monitors the level of the stream and signals that the level is rising before any damage occurs. In fact, if I could act before the calamitous event, I could move the car to a safer area and try to save the most delicate objects and furniture from the water. That way I could limit the damage.

The basic idea is to monitor the water level of the stream and, to do this, a simple resistive sensor would suffice. If water wets the sensor, the alarm is triggered. In a more complete version, on the other hand, an array of sensors could be created a few cm away from each other that not only detects the water level more precisely, but also allows you to calculate the gradient with which the water level rise, allowing you to predict the extent of the calamitous event and have a forecast of the final water level and the time remaining.