Re: ‘No Flood Plan for Mariental’ – New Era 17 October 2006 The Mariental Flood Task Force (MFTF) and its chairman have to find a solution for the largest dam in Namibia, fitted with sluice gates and the Fish River below the dam that is dogged up by reeds and sediment, so much so that only 20% of the carrying capacity of the river is left! Instead of transporting about 200m/sec (before the dam was built), it now can only accommodate a flood of about 400m/sec. Your readers might remember the break-thunderstorm that hit Windhoek in the afternoon of the 15th October 2006. Certain areas in Klein Windhoek and a supermarket were flooded. The reason? Dogged run-offs! The chairman has the cheek to mention the flood of 1923. He does not tell your readers the peak flows of that year or the fact that it was well below all the floods that hit Mariental after the dam was built! According to him, the flood of 1923 had a peak of 95ÃÆ’Æ‘ÀÃ…ÃÆ”šÃ‚ 000 cubic feet/sec. This works out at 2ÃÆ’Æ‘ÀÃ…ÃÆ”šÃ‚ 690m/sec. With a clear river this would mean some 700m/sec. more than the capacity of the Fish River at that time. Neither does he tell the readers the duration of the flood. Against his crown witness, I will furnish you with the facts of the 2006 flood: The peak that was released through the sluice gates was about 300m/sec above the carrying capacity of the river below the dam wall. The duration of Mariental’s inundation was more than 48 hours! Your readers might be interested to know that the 2006 flood could not be avoided, even if the Hardap Dam was bone dry. The reason for this calamity is the fact that the Fish River can only carry about 20% of its capacity because it is dogged up by reeds and sediment. If the carrying capacity of 200m/sec would have been restored, the flood of 2006 could have been avoided, if the sluice gates were opened as soon as the first reports from the catchment area were received! According to the chairman of MFTF the “problem has been in existence for many years already”. Indeed, the people responsible are at sleep for at least 15 years and fast asleep for the past six years. The cost of clearing the river is estimated by him as N$200 million to frighten off any argument against this only solution! And if nothing will be done in this direction, the costs resulting from flooding and clearing will increase year by year. I am sure that if the people of Mariental would get a quarter of the N$200 million, the chairman of MFTF would be surprised by the result! The arguments he produces is a smokescreen, and if one has to wait until next July for something to happen then the Task Force has to rename itself. Prof. Dr. Erich FÃÆ’Æ‘Æ‘ÃÆ”šÃ‚¶rtsch Swakopmund