Water Level Control and Tidal Flows

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Although structural limits (the dam and narrow channel) are still in place, operational limits to unrestricted tidal flows have been reduced compared to previous decades and the past century. This has led to improvements in water quality.

At present, natural tidal flows are allowed except that incoming high tides are prevented from entering the Lake when rain is forecast in order to provide flood control. This can occur for several days to several weeks at a time. Tidal flows are also restricted to keep the Lake at a high level for seaweed harvesting, for boat races and during unusual circumstances.

Impact of Limited Tidal Flow on Oxygen Levels and Proposed Wetlands: Although Lake stratification and low bottom oxygen levels can occur during both limited and normal tidal exchange, existing data clarify that restricting tidal flow for flood control purposes can significantly lower oxygen levels in Lake Merritt. In addition, restrictions on natural tidal flows should be minimized in order to insure the survival of any wetlands that may be established at the Lake.

2002: Options for Control of Tidal Flow and Lake Level

We have learned much from our efforts to control the level of Lake Merritt. As the 21st century begins there are opportunities (such as described in the Channel Study and Master Plan) to re-evaluate current operational limits to tidal flows and to redesign and re-locate the flood control structure.

The Channel Study: Alternatives 1 - 4 of the Channel Study (Port of Oakland, 2002) include several modifications that would greatly improve tidal flow to Lake Merritt.
These include:

• Replacement of the “bottleneck” culverts at 10th Street with a bridge
• Dredging the channel from the Lake to the Bart tunnel, lowering the outlet by 1.88 feet
• Replacing the flood control structure with a new facility at 12th Street
• Improving other road and utility crossings over the channel. Next >>

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