Efforts more upstream and around the border building are going to be recovery. Satellite imagery, drone overflight would be able to provide a good first assessment. Capabilities well within the Chinese military. FLIR equipped aircraft could pick out survivors on higher ground, if there are any. Whether or not China has these aircraft in theatre is unknown. Given the sheer volume of water running through the narrower valleys, the outcome is a forgone conclusion. Just a matter of when the Chinese is prepared to call it a recovery effort.
Further downstream where my the valley opens up, the water can spread out and there was also time for people to run to higher ground. Rescue is more probable here. Helicopters would be useful here but there must first be helicopters available and I doubt Nepal has them in enough numbers. Hopefully Nepal would accept more foreign assistance.