How to prevent floods in Nepal

Glacial tsunamis were frequent events even at the end of the Ice Age 10,000 years ago, and they are presumed to be the origin of the great flood legends found worldwide.
The problem is how to prevent them. What if we tried a method of slowly draining the water from glacial lakes located on the mountains?
If we connect a hose and position one end lower down, the water will continue to drain even without power—much like what we used to do often in the bathtub as children.
We must reduce the volume of water as much as possible.