On Web-ct there is an article scanned from a recent edition of the Wall Street Journal (front page). This assignment is an opportunity to enjoy and easy article, pick up points, and think. Think about the following questions and write not more than a 2 page report. Be thoughtful!

A. What sub-disciplines of civil engineering are mentioned?

B. Sediment transport is important in hydraulic engineering. What are the effects mentioned in the article to both the reservoir and downstream areas? Does what is discussed in the article have any implications near us - say New Orleans?

C. From your knowledge, what are the engineering issues that need to be investigated?

Perhaps the most important engineering issue regarding the Three Gorges Dam is to prepare to implement an emergency demolition plan to bring the structure down safely in the event it begins to fail catastrophically on its own. The devastation an uncontrolled failure of this dam is likely to wreak on downstream inhabitants is tremendous, and the likelihood of such failure continues to grow as more unanticipated problems are discovered to add to the extensive list of the problems known and suspected before construction.

For example, it isn't surprising to those who have followed the planning and construction of the Three Gorges Dam that sedimentation is becoming a problem. That dams trap sediment is not news, nor is it difficult to apply a basic mass-balance equation; the silt trapped behind the dam will not be flowing downstream as it used to do. If downstream estuaries and flood-irrigated areas were neither shrinking nor growing with the amount of silt washed downstream without the dam, it is likely they will shrink when the silt load is decreased. In addition to the downstream problems, silt accumulates behind the dam. All of this was known beforehand, but now scientists can begin to quantify these effects, and engineers can ponder how to mitigate them. If the Mississippi delta region is to serve as a precedent, the value of emergency planning in the event of failure far exceeds the value of figuring out how to solve these problems since the likelihood of meaningful action is small in comparison to the probability of failure.

More interesting and a bit more surprising is the effect of cyclic inundation, compression under water pressure, relaxation of this pressure, and subsequent drying of some parts of the reservoir due to the fluctuating water level. Geotechnical experts will need to do a 'heckuvajob' to understand the consequences of this kind of dynamic soil and strata loading. Though studies of the region are likely to result in plenty of publications, again it seems unlikely this will motivate any kind of meaningful remedial action. If New Orleans is typical, expect public and private scientists and engineers to have a pretty good idea of what needs to be done to make the system work, and the central government to underfund the maintenance and play politics with what resources are allocated. Perhaps the best public policy would be to build a casino district or other playground for the wealthy on the reservoir. A small threat to a few wealthy people is always taken much more seriously than a great threat to many more modest folks.

In the meantime, besides documenting the Three Gorges Dam project for historical and scientific reference, scientists and engineers who would like to make a more meaningful contribution to the health and welfare of effected residents may wish to help prepare plans on how to deal with the more serious possible catastrophes and leave the temporary quick fixes to the politicians.