From Harald Kreuzer, Swiss National Committee on Large Dams
Pearce’s assertion about the Concepción dam, namely that “floods in
Tegucigalpa . . . were seriously exacerbated when engineers made an emergency
release of water from the Concepción dam” can easily be refuted by the
fact that this dam has only an ungated crest spillway and a small outlet at the
bottom for drinking water. It is therefore impossible to create an artificial
flood. The “wall of water” that the survivors describe having seen was actually
caused by a rock slide into the Rio Grande upstream of the city.
Secondly, the benefit of the El Cajón multipurpose arch dam in
Honduras during Hurricane Mitch is not mentioned. Upstream of this dam, which is
226 metres high, damage was substantial, the worst
event being a major landslide above the town of La Libertad which caused
considerable loss of life.
The owner of El Cajón dam estimates that the incoming flood to the
reservoir was 9800 cubic metres per second—likely to happen only once
every 500 years—and 70 per cent of the probable maximum flood. The
reservoir level prior to the passing of the hurricane was 13 metres below full
supply level. Within 70 hours this level had risen by 16 metres, and some 1500
million cubic metres of floodwater had been retained.
As a result of this flood control, the maximum discharge experienced
downstream of the dam was only 1200 cubic metres per second. The presence of the
El Cajón dam, and its appropriate operation, thus considerably reduced
downstream flood levels.
Advertisement
Brunegg, Switzerland
