Dam studies don’t dig deep enough on impacts to tributaries, says Sound Science report

Monday was the deadline for comments on 14 remaining studies proposed by the Alaska Energy Authority to analyze and predict the impacts of a hydroelectric dam on the Susitna river. So far, 20 Federal, state, professional organization and individuals have submitted reviews of the 14 studies.

One review was prepared by Sound Science, LLC, on behalf of the Coalition for Susitna Dam Alternatives. As KTNA’s Lorien Nettleton reports, Sound Science found gaps in the proposed study plan regarding what effect lower water flow on the main channel would have on the side-streams and tributaries.

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David Braun is a specialist in Eco-Hydrology, which is the study of the interaction between flow-patterns of rivers and how they work as ecosystems. Braun conducted the Sound Science review, and has a long background in studying the impact of geomorphology – or water flow, sediment load – and its effect on the habitat and subsequent ecology of rivers. Braun describes impacts on tributaries as unavoidable, when there is a change in the water flow of the main channel:


Braun says during his review of two of the studies, he didn’t see an adequate appraisal of what changes in water flow on the Susitna would have on the erosion of the tributaries.


Another section that Braun describes as critical it understanding how water flow changes alter the habitat for spawning salmon as under-studied. One AEA study calls for a mapping of the river’s features, such as rocks, rapids, riffles, pools and other large landmarks, and hopes to use these to guess on where salmon spawning habitat would be. Braun says it doesn’t look close enough, that salmon habitat selection happens on a smaller/finer scale


Coalition for Susitna Dam Alternatives member Rick Leo points out that the detailed review in Sound Science’s 54-page report covers just a small portion of the studies necessary to understand the impacts of the dam.

Clip: 4Dam

Sound Science’s report, like most of the comments filed on the 14 additional studies, is technical, and exhaustive. KTNA will have a look at other reports in coming newscasts.

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