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 Wetlands.

Orthophoto Quadrangles (DOQ), and

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 (http://www.inforain.org/siuslaw/) coast range.

Total Drainage Area

Watershed Statistics

Length of watershed Width of Watershed Length/Width ratio No. of Sub-basins in Watershed Average Area of Sub-basins Total No. of Stream Segments or Tributaries 445.5 km 2 m 2 ) 21.2 km (445466105 41.1 km 0.515

22 20.2 km 2 3407 Total No. of First Order Stream Segments 1758 Total No of Second Order Stream Segments 806 First Order Stream Frequency 3.9 per km 2

Elevation and Slope Minimum Watershed Elevation 0 ft (sea level) Maximum Watershed Elevation Minimum Slope Maximum Slope 712.5 ft 0° 68.1978°

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.

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.

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.

Resources

DEM and DOQ http://libweb.uoregon.edu/map/map_section/search.html

DRG http://libremap.org/data/state/oregon/drg/ Precipitation Data http://prism.oregonstate.edu/ Soil Data http://www.or.nrcs.usda.gov/pnw_soil/or_data.html

Streams Data http://www.wou.edu/las/physci/taylor/es341/coast_streams.zip

Watershed Data http://www.wou.edu/las/physci/taylor/es341/coast_sheds.zip

Geologic Data http://tin.er.usgs.gov/geology/state/state.php?state=OR Vegetation data http://www.oregon.gov/DAS/EISPD/GEO/alphalist.shtml