(
Satellite)
Dec 2025 Flood:
Most big dams have multiple functions. This one has just one function --- flood control. This is the upstream side of the dam and the reservoir is empty except for the normal flow of the river.
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USACE
"The core of the dam is a compacted blend of sand, gravel and glacial till. Upstream and downstream sides of the dam are crushed rock covered by large quarry rocks. The massive weight of the rock holds the core firmly in place. Two tunnels channel the river around and under the dam. A 9-foot-[2.7m]wide tunnel passes normal flows [including sediment]. A 23-foot[7m]-wide tunnel is used during periods of high flows and during floods." |
This view is from the other side and it shows that the dam is holding a pool.
This is a comparable view but the pool is empty. Note that the pool above is almost to the top of the round tower.
Why can't the fish use the 9' (2.7m) tunnel to pass through the dam?
$112m was spent for a trap-and-haul facility for the Chinook run. [
USACE]
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USACE, Seattle District posted
Mud Mountain is a "dry bed" dam with a primary goal of remaining as empty as possible. During a drawdown here, our water managers must also manage sediment and debris. Using specialized tunnels, we "flush" glacial flour (fine-grained, silt-sized rock particles) and wood through the dam to maintain the reservoir’s capacity and ensure the White River’s natural ecosystem remains healthy. |
I could not find an explanation of what gets flooded downstream at the various phases of discharge.
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Michael Snyder tweeted
White river from Mud Mountain dam release, still flooding local areas and may get worse in Auburn/ Kent areas. |
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2:15 video @ 0:21
The person being interviewed says the river is higher than he has ever seen before. |
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