Rain Gauge, Water Flow Sensor, Silting Sensor in Railway

Hello !

I have to develop some sensors for assessing the water level, the water flow and level of sedimentation on the aqueducts level and I'm looking for some documentation on sensors that are in use right now in other countries for example Holland or Canada.

I've searched a lot on the internet but I can't find references for the sensors or specific examples of systems (sensors and softwares) that are used by railway compagnies so that they'll be able to limit the need for maintenance.

I'll be really thankfull if you could help me find those informations.

Thank you in advance.

Have a good day !