Lower Coquille Watershed
Prepared by:
Sandi Biester, Mark Johnson and Richard Lowes
ES 341 Fundamentals of Geographic Information Systems
Hydrologic Summary
The Watershed
The Lower Coquille Watershed is 1059 Sq. miles in area, it is the largest watershed to
originate in the Oregon Coastal Range.
The majority of the watershed lies within Coos County, with small areas touching on
Douglas and Curry Counties. The river contains three major tributaries; the North, the
Middle, and the South Forks. They join the mainstream, and flow into the Pacific Ocean at
Bandon1.
Total Drainage Area (sq meters): 269,258,378 m2
Total Drainage Area (sq. kilometers): 269.25 km2
Total Length of Watershed (sq. kilometers): 28.317 km
Total Width of Watershed (sq. Kilometers): 23.93 km
Watershed Length/Width Ratio: 1.183
Total Number of Subbasins in Watershed: 12
Average Area of Subbasins in Watershed: 22.438 km2
Total Number of Stream Segments or Tributaries in Watershed: 1613
Total Number of First Order Stream Segments: 815
Total Number of Second Order Stream Segments: 381
First Order Stream Frequency (total number/Drainage Area: 3.03 per km2
Lower Coquille watershed DRG
Lower Coquille Watershed DEM
Conclusions
Currently the population within the watershed is about 16, 801 people. The
population is concentrated in the valley areas with the majority of clustered
around the incorporated towns of Bandon, Coquille, Myrtle Point and Powers.
The more densely populated areas are confined to the flood plains along the
main stems of the watershed. The watershed contains a large area for
agriculture and forestry production. In fact the large Coos Bay timber industry
grew up because of the timber out of the watershed area5.
You can insert
Watershed Location
Coquille Watershed is in Coos County with sections in Douglas and Curry
Counties
Lower Coquille Watershed Vegetation
Lower Coquille Annual Precipitation
Physiography
Approximately 70% of the Watershed is Forested. The coniferous forests on productive
soils and slopes in the basin are mostly Douglas Fir; however, Port Orford Cedar is also an
important component of the forests. In the lowlands the forests are made-up of oak
savannas in the drier areas and Douglas Fir, cedar and hemlock in the wetter areas. Land
uses in the valley areas are mostly residential and industrials sites, crop and pasturelands,
and gravel extraction. Pastureland does extend into the hills above the flood plains in
some areas. The steep slopes above the valleys are very sparsely populated. Timber
production, agriculture and some mining are the predominant land uses4.
Lower Coquille
DOQ
Bedrock Geology of the Coquille Watershed
Soil classification of the Coquille Watershed
References Cited
General Geology
The Coquille Watershed was created by a combination of events that occurred following
the last Ice Age. A high sea level caused the valley to be clogged with sediments to give a
series of valley-fill materials which form the Coquille Formation. The Watershed is
comprised primarily of deep, silty loams, silty clay loams, and clay loams which is prone to
erosional processes. An exception to this exists on former marine terraces which are
comprised of sandy and sandy-loam soils. These areas are prone to wind erosion as well
as water erosion2.
Most of the formations are sandstone; however, the Looking glass formation is
conglomerate at the bottom and transitions to sandstone at the top. The various bedrocks
shown all have naturally high sedimentation rates3.
Watershed Parameters
Minimum Watershed Elevation-0 Meters
 Maximum Watershed Elevation-516 Meters
 Minimum Slope (decimal degrees)-0 degrees
 Maximum Slope (decimal degrees)-59.50 degrees

1.Coquille Watershed Association http://www.coquillewatershed.org/Coquille_Facts.html
2.Natural Resources Conservation Service http://www.or.nrcs.usda.gov/programs/csp/csp_data/2005/coquille-factsheet.pdf
3.Pacific Coast Watershed Partnership http://www.pacificwatersheds.net/coastalnetwork/coquille.htm
4.Pacific Coast Watershed Partnership http://www.pacificwatersheds.net/coastalnetwork/coquille.htm
5.Introduction to the Coquille Watershed http://www.coquillewatershed.org/Coquille_Facts.html