Well all the info that I have had so far suggests this :
Historically Koshi was a matter of debate during the British rule in India. They were in two minds whether to construct a barrage or not. Finally they thought it's wise to let it follow the natural course.
Reason: Koshi while following drags a lot of sediments when it flows down south, thus raising the level of river and requiring more room to manuever. Plus it's one of the MOST VIOLENT rivers in the world, let alone Asia.
After the construction of barrage: which essentially confines the flow, the Koshi Treaty was done whereupon it's India's responsibility to take care of the maintenance and rehab. of the structure.
Technical/design flaw: Koshi should have been left alone.
Maintenance flaw: Though the treaty was between India and Nepal govt. the project has handed over to the State of Bihar. In today's time when Bihar is one of the worst states in India, totally failed to be upto the task of taking care of the maintenance.
The structure has capacity to sustain a huge flow (9.5 lakhs cusec, I am still not sure about this number).
The Nepalese engineer so many times reported Bihar counterpart for maintenance but they turned blind eye. He was so pissed he wrote a letter to embassy and Narayanhiti.
The Indian team, though very late, came to check on the maintenance but were threatened by the locals in Nepal (u know those typical contractors and so) and left for their safety.
Result : At a flow much less than the capacity, the disaster happens. That's totally ridiculously stupid. The blame game can go, but as long we are third world countries, and have attitudes like this where the structure is constructed and thereafter everyone can go to hell, these disasters will hapeen again and again and again.
One only needs to look at Hurricane Gustav. The FEMA, Gov of LA Bobby Jindal, even Presiden Bush, national guard has such a terrific coordination among their respective federal, state level, and local levels that it's an example as how to minimize the impact of a natural disaster.
We can't stop a natural disaster from happening, but can surely do a lot to minimize it's effects.
They learnt from Katrina experience, thus evacuation, safe passage, law and order prevailed ....and guess what levies didn't fail this time which were reconstructed by Army Corps of Engineers.
Well an investigation needs to be done to see who is at fault and they need to be tried in court.
BY THE WAY RAJESHKC, INTERESTINGLY, WHICH HYDROPOWER PROJECT U R TALKING ABOUT THAT WOULD HAVE PREVENTED THIS INCIDENT. FOR HYDROPOWER PROJECT, U YET AGAIN HAVE TO CONSTRUCT A DAM. WHERE DO U THINK THE DAM SHOULD HAVE BEEN CONSTRUCTED, AND WHAT WAS THE CHANCES THE DAM WOULD MINIMIZE THE LIKELIHOOD OF A REPEAT OF THIS INCIDENT.
JUST CURIOUS , COULD U PLZ ELABORATE.