Sir we can not build big dams on Chenab. We may be able to create lakes but that would require massive funds and I doubt any neutral level lake can absorb such big floods. We may not have the area required either for such lakes. I am not an expert of hydrology, and I would welcome expert opinion on this matter.
If you can't build dams, the Lakes are never prohibited, supported by a canal dispensing system. For example, say your river's capacity is 500,000 Cusec, and you have 400,000 Cusecs coming in, you'll have a total of 900,000 Cusecs say between Day 5th and 7th of a month.
Now even if the river comes in from India, the Weather Doppler radars (each TV station in the US has one), can be placed around the border. Kashmir is a mountainous region so putting such a small system on top of a hill or a mountain can accurately tell you the Rain patterns, precipitation, humidity, cloud density and expected water density around 75 to 100 miles (about 115 - 145 KM?) out, so that's a LOT of area.
Now on Day 3, you know there are significant clouds that can bring down rain from 2-8 inches (Estimated). You take the median in this case (as supported by the history in a geographical area) and let go of the water 200 KM's away from 4 large reservoirs. Here is how it works:
1) Empty out about 200,000 Cusecs waters from the lakes down stream towards Indus or the Ocean, leaving the lakes almost 75% empty. After this water is slowly pushed out with increments (to avoid flooding in Indus on its way towards the ocean), you take the next steps.
2) Start to empty out the two - three main rivers that come straight from the Kashmiri mountains. The water coming down from the mountains will have tremendous force which will double the impact due to downward slope movement. You start to empty out these rivers through long or circular canals (so water remains in transit for a while before getting inside the reservoirs), then these Reservoirs get filled up again and you empty them out. Leaving 100,000 Cusecs (or less if the magnitude of rainfalls inside India and Pakistan has been determined and increased).
3) Now the rainfall water won't have its own impact to the river as the Rainfall water continues to drain away through this canal system to the reservoir then to the Indus or the Ocean so its "forward moving" water, which is good, compared to the accumulated water in one place which results in an immediate overflow when a surge happens.
4) Now your river bed is empty almost by day 5 and its started to receive flood water coming from up-stream. As you see the trend and force of this water, you keep using the canal system to push the water out to the reservoirs and then out through Indus and to the ocean.
5) Now 500,000 thousand Cusecs can easily be accommodated as there are two constant exist channels out for flood water, (1) is the natural river trajectory that eventually takes it to the Indus / the Ocean and (2) the canal based system and associated water reservoirs that are not letting the water accumulate in one place
6) On day 8th, the major water surge would have passed through the normal river flow and through the canal and the reservoir system. You may have (5-10%), 50,000 or 100,000 Cusec water that may still flood due to rare extreme situations but the there won't be insane devastation anywhere. 50 to 100K cusecs means half a mile worth of water pools / swaths spread across certain areas designed to release the flood water to protect the population.
7) On day 10 or 11: You'll have FRESH water (Spring Fed) reservoirs up to date with Fresh water that you can use all year round for providing clean water after purification (as its all rain water, which is pure with river mud that can be cleaned and water can be Chlorinated to kill germs and all).
The reservoir system provides an excellent opportunity to save water for Drinking, Irrigation, build Agriculture, Seafood, Poultry, Beef and Fish farms around these reservoirs, parks and recreational activities with wild life (Where people come and enjoy their day and pay for entering so more revenue is generated).
This all sounds complicated but its really one canal system with branches and a few large lakes without the expensive "DAM" type infrastructure. The benefits are A LOT more than the investment.
