1. Lower Siuslaw River Watershed
Lane and Douglas Counties, Oregon
Tim Lundy and Joey Doyle, Western Oregon University
Introduction
The purpose of this poster is to represent several interesting facts as well as provide different map styles to show different themes of the Lower Siuslaw Watershed. The map themes include USGS Digital Raster Graphics(DRG), USGS Digital Elevation Models(DEM), Bedrock Geology, Annual Rainfall/ Precipitation, soils, Vegetation, Roads, Streams, Digital Orthophoto Quadrangles (DOQ), and Wetlands.
Location
The Lower Siuslaw Watershed is a subbasin of the larger Siuslaw Watershed and is located in Northwest Oregon in Lane and Douglas counties. It covers parts of the Mercer Lake, Tiernan, Mapleton, Greenleaf, Goose Pasture, Florence, Goodwin Peak, Baldy Mountain, and Roman Nose Mountain quadrangles.
Physiography, Geology, and Hydrology
The underlying geology is almost entirely layered marine sandstones, known as the Tyee Formation. This is a soft, erodable rock that, when combined with the high seasonal rainfall and steep slopes is subject to landslides known as "debris flows". The overall shape of the land, with relatively level but narrow valleys flanked by steep low mountains with knife-edge ridges, is a result of this interaction. The Coast Range is still actively rising, but the main streams have the power to carve out low-gradient paths through the mountains to the sea. The Siuslaw is one of only a few rivers that has managed to cut a path entirely through the coast range. (
Digital Raster Graphics (DRG)
Watershed perimeter overlaying digitized standard 7.5 minute quadrangles.
Digital Elevation Model (DEM)
Elevation data is stored in each pixel and can be colored or shaded to convey information; e.g. absolute heights, slope angle, or to emulate physical structure. This DEM is at 10 meter resolution .
Digital Orthophoto Quadrangles (DOQ)
Georectified aerial photographs by quadrangle.
Soils
Soil distribution throughout the Lower Siuslaw Watershed.
Geology
Bedrock types with roads overlay.
Climate
Average precipitation shown in inches per year with streams overlay. Heavier rainfall shown in purple, lighter in orange. Streams classified and sized by order.
Watershed Statistics
Total Drainage Area
445.5 km2 ( m2)
Length of watershed
21.2 km
Width of Watershed
41.1 km
Length/Width ratio
0.515
No. of Sub-basins in Watershed 22
Average Area of Sub-basins
20.2 km2
Total No. of Stream Segments or Tributaries
3407
Total No. of First Order Stream Segments
1758
Total No of Second Order Stream Segments
806
First Order Stream Frequency
3.9 per km2
Resources
DEM and DOQ
DRG
Precipitation Data
Soil Data
Streams Data
Watershed Data
Geologic Data
Vegetation data
Elevation and Slope
Minimum Watershed Elevation
0 ft (sea level)
Maximum Watershed Elevation
712.5 ft
Minimum Slope 0°
Maximum Slope °
Vegetation
Types of flora, dune areas, urban development, and open water are represented.
Streams and Subwatersheds
Watershed drainages and associated streams are shown. Drainage boundaries in yellow; streams classified and sized by order.