15 June 2010
I will shortly post the latest update on the monitoring site, which shows that the lake level is continuing to rise at about 5 cm per day as inflow exceeds outflow. The spillway continues to show a remarkable level of stability. These two images compare an image from Sunday (left side) with one taken 24 hours later on Monday (right side). Whilst it is tempting to play spot the difference, the reality is almost no change:
So what to do now? Well, it is clear that there is a huge social cost to the current situation, which probably cannot continue for much longer. It is also surely clear that the current monitoring team cannot maintain the current level of activity for long given their living conditions. So here is my suggestion for a way forward. Please note this is not advice, and should not be treated as such, but rather it is a starting point for discussion.
1. NDMA sets up a detailed, integrated data collection system based upon, but enhancing, the current Focus activities. This should include the following measurements at 6 hour interval:, with the first measurement each day being taken at dawn
- The flow rate in the spillway
- The seepage rate
- The lake level
- Landslide activity
- The inflow rate
- Seismic activity
2. An expert group meets just after dawn each day and integrates that data with the weather forecast to issue guidance on the stability of the dam. If the group considers that conditions are safe, the boat service is allowed to operate, and people are allowed onto the red zone – i.e. the land below the dam – during the hours of daylight, so long as they are within earshot of a siren.
3. This is backed up with real time monitoring, preferably automatic, of inflow, landslide / rockfall activity at strategic points along the lake, and outflow, feeding a warning system. A command centre is established that would operate the alarm system should landslide flow rate increase. Boat crews and people in the red zone are trained as to what they should do if the alarm sounds.
4. The expert group meets at dusk each day to plan for the next day.
5. Alongside this a study is implemented immediately of management options for the spillway. This study should be undertaken properly, with international input, and will be made openly available when complete. A timetable is placed on the production of this report, and on the decisions that will be made on the basis of it.
6. All of this is backed up with a transparent communication strategy that explains the risks and benefits of the current situation, and of the various options.
This would seem to me to be the best balance between maintaining safety and allowing people to start to rebuild their lives. Of course this strategy will increase the risk that people face from the dam – but there are real risks associated with their displaced state too that we need to start to reduce. However, I must emphasise that to do this safely NDMA must use expert advice – this cannot be done any other way.