Sandy River Delta Dam

From Portland Hikers Field Guide

The Sandy River Delta Dam (Steve Hart)

Sunset over the old channel (Steve Hart)

Hikes including this location:
- Sandy River Delta Hike (TH | <-- --> | LOG)
Latitude: 45.55478
Longitude: -122.37830
Maps: Portland Hikers Maps Google Earth
Elevation: 10 feet

1 Description
2 Trip Reports
3 Related Discussions / Q&A
4 Guidebooks that cover this destination
5 More Links
6 Contributors

Description

The Sandy River Delta was formed by mudflows originating on Mount Hood and flowing down the Sandy River to the Columbia. The most recent of these mudflows was about the year 1800. By 1900, the delta had been reworked by floods on the Columbia, as well as a constant stream of sediment coming down the Sandy River as the river cleared its channel. The larger part of the river flowed under the railroad and highway bridges and about a half mile north. At that point, it veered east and entered the Columbia River almost two miles east of where it does today. A secondary, smaller channel existed where today's current channel exists.

In 1904, a large flood partially blocked the secondary channel and it began to run dry during the fish runs. In an effort to help fish runs, a dam was built in 1931 that completely blocked the main eastern channel. In this way the river was forced in its entirety into the former secondary channel. The original dam was a 750 foot wide, five foot high barrier constructed of piling. In 1938, the dam was improved to a 10 foot high structure filled with riprap. In time, continuing erosion filled the old river channel with sediment. Today the dam is nearly buried in sediment and only the top is visible, used as a road by power line maintainers and a trail by the rest of us.

More modern looks at the fish runs question the value of the dam. There is talk of removing the dam and allowing the river to return to its original channel.