Radar Altimeter
The radar altimeter payload is based on the Geolux LX-80 instrument. The radar altimeter can be flown in autonomous mode at an altitude of 30-50 meters along the river and provides water surface elevation profiles with centimeter accuracy. Because water is an excellent reflector of microwaves, the radar return will be dominated by water targets. If there are any water surfaces within the footprint of the sensor, those will dominate the return signal.
The radar altimeter is commercially available from SPH here.