by Mahinda Samarasinghe
---- — As a new resident to Traverse City, I became aware of the Boardman River Dams project involving three dams identified for removal. I wondered if adequate hydrological studies had been carried out on the Boardman River. Although a fair amount of literature was found online, reference to a comprehensive hydrologic study was not encountered. In downtown, where the river flows with a narrow width, the potential for major flood damage seems high.
A comprehensive hydrologic study should not only consider a maximum design rainfall in the Boardman River basin, but also the absence of the three ponds and consequent sedimentation of the only remaining lake (Boardman), reducing its water retention capacity. Furthermore, design peak rainfall amounts and duration should be chosen prudently, considering the flood disasters experienced by adjacent Midwestern states in recent years.
A lesson we could learn from the recent Fukushima Nuclear Power Plant disaster in Japan is that, in designing the protective wall for the nuclear plant, the engineers had grossly underestimated the tidal wave height compared to the actual height of the tsunami wave of March 2011 (PBS TV program).
All the sophisticated engineering designs were rendered useless in the face of that tsunami tidal wave, which destroyed the nuclear plant and caused deadly radiation leakage with colossal damage to life and property.
Absence of the other three dams and resultant sedimentation will possibly lead to high water levels at Boardman Lake, whose normal water level is only a few feet below the ground level. Hence, a major flood can pose a serious threat to numerous buildings in Traverse City. There need to be reassurances to citizens this will not happen.
Sedimentation: Siltation of the Boardman Lake and thus, Lake Michigan, can occur due to sediments carried along the river when the dams are breached. A partial drawdown that has already been effected at the Boardman Pond now shows many tell-tale signs of distress, such as loss of scenic beauty and recreational facility and erosion of the embankments, causing increased sediment loads on the river. The warning signs posted at the site attest to the latter.
A sediment load study should incorporate the erosion of sandy subsoils after removal of the three dams. Any sediment transport studies carried out without consideration for the erosion resulting from the dam removal will not have much relevance. Ironically, dams are often built for sediment control.
Other considerations: Prudent attention is also needed in: a) management of the fish populations, b) not disturbing the pollution embedded in the sediments, and c) tapping clean hydroelectric energy by repairing/upgrading the dams. Building a dam is much costlier than removing a dam. Thus, the removal of existing power-producing capacity at the dams goes against conventional wisdom. Clean energy needs to be promoted, and not shut down, in this time of pollution leading to adverse climatic and associated changes on Mother Earth. Any disastrous consequences resulting from dam removal could incur huge costs to the community in the long run.
About the author: Mahinda Samarasinghe, a retired civil engineer, obtained a Ph.D. in Geotechnical Engineering from the University of Kentucky and has worked in Australia and Sri Lanka as a civil engineer.
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