DESCRIPTION:
Green River Drainage, Mount St. Helens, Washington

[Map,20K,InlineGIF)
Major Hydrologic Features in the Mount St. Helens Region -- Modified from: Crandell and Mullineaux, 1978, USGS Bulletin 1383-C

The Green River occupies an eastward trending valley north of and sub-parallel to the North Fork Toutle River valley. The drainage basin heads in rugged metavolcanic terrain northeast of Spirit Lake. Half the Green River drainage was significantly altered by the lateral blast of the May 18, 1980, eruption. Severe timber blow down and tephra deposition occurred in much of the affected area. Air-fall ejecta from this eruption was deposited to thicknesses greater than 0.50 m in the headwaters of Shultz Creek drainage ... The northwest end of the basin received no tephra from the May 18 eruption, and only a thin veneer of ash on May 25, 1980 (Waitt and Dzurisin, 1981; Waitt and others, 1981). Additional unconsolidated sediment was produced when the Green River was ponded behind the North Fork Toutle lahar, about 2.5 km upstream from the mouth. As much as 2 m of sand and silt were deposited in and near the channel along this reach.

A gaging station (hydrologic data collection site) was re-established on the Green River in September 1980, 3.2 km upstream from the mouth, to collect water and suspended-sediment discharge data. Seventeen cross sections were installed the summer of 1980 to monitor changes in channel geometry, (Meyer and others, 1985). The cross sections were grouped into four clusters: above Grizzly Creek reach, Polar Star Mine reach, Shultz Creek reach, and the Hatchery reach. Four cross sections were added to the network in 1982 along the Gage reach; three cross sections were added along the lower Grizzly Creek reach in 1984, and two cross sections from the 1982 network were lost. ...

Return to:
[Green River Menu] ...
[Mount St. Helens River Drainages Menu] ...