In a fascinating interview with the Kathmandu Post, Dipak Gyawali, former Water Resources Minister of Nepal, who has been working on water resources for two decades analyses what has happened and what is to come.
"I doubt it, simply because the breach now is no longer a rupture in the side embankment that can be plugged once the water level goes down and the Koshi starts flowing along its original main channel. What we are seeing is the main stem of the river itself flowing through it, capturing centuries' old channel and changing its course. To change it back is like damming the Koshi anew with a new barrage, in addition to making the river do a "high jump" of at least four meters to flow along its recently abandoned bed. Believe me, it won't be too happy doing that now or in the coming years, and will find some way to continuously breach the embankment in other weak spots, and no engineer can guarantee that this won't happen, although they will have lots of fun playing with all kinds of expensive toys "to tame the Koshi".
The problem now is no longer just the breach at Kusaha in Nepal: it is totally uncertain where the new Koshi channel will be in the middle and lower delta in Bihar. Currently, satellite pictures show that it might be moving along the Supaul channel; but I think this might just be a massive ponding that is occurring with Koshi filling every depression, canal, old oxbow lake or the space between the indiscriminately built embankments. Since the land naturally slopes eastwards, depending upon whether the coming September floods are a four lakh cusecs flood or a nine lakh one (as happened in 1968) the new Koshi could be as far east as Katihar. Even if it does not go that far this year, it is inevitable it will do so in the years to come. This river morphology dynamics has to be looked at before any new embankments or repairs of old ones can be considered. "
"The immediate requirements of Nepal and Bihar (and by immediate I mean from now till ten or so years) will have to be met by new and alternative technologies suited to an unstable but very fertile flood plain. Such adaptive technologies with strong social components have been traditionally used by people in the form of houses on stilts and building villages with raised plinth levels that keep life and property safe but allow the flood to easily pass by leaving fertile silt behind. It will also call into serious question the current design practices in the transportation, housing, agriculture and other sectors, forcing the adopting of new approaches that look not so much to the watershed but to the 'problemshed' for answers. There is nothing called a permanent solution (how 'permanent' is a permanent concrete dam, after all?); but building houses on stilts is a cheaper, more 'doable' and thus a better solution. "
Full interview below