About the Forest
About the Forest
Andrews Watershed 1 - WS01
Andrews Experimental Forest (HJA)
Watershed above the Watershed 1 gaging station
Bounding Coordinates (decimal degrees):
Slope (%): 59.35
Aspect (degrees): 286
100% clearcut over a four-year period from fall 1962 to summer 1966. Skyline yarding was used and no roads were constructed in the gaged portion of the watershed. Slash was burned in October, 1966. Skyline yarding equipment removed timber from the entire 237 acres of the watershed. With this method, the back end of the logs are dragged to a fixed overhead cable, then lifted free of the ground for transport downhill to the landing. No roads were constructed in this watershed. Debris burning in October, 1966 consumed most of the fine logging debris on the slopes and that accumulated in the stream channel. The control watershed is the adjacent WS#2. Gaging stations are about 1.15 km apart. The control is about 63% the area of WS#1. GIS estimated percent harvest: 95.5%
Glacial, fluvial, and mass wasting processes have affected soil development and spatial distribution, particularly in geologic contact zones and steeper areas of the HJA. Infiltration rates are high and non-localized overland flow has not been observed in any of the watersheds. In Watershed 1, soils range from shallow and stony with little profile development to moderately deep with well-developed profile features. Shallow soils predominate, though they are often located on deep (> 3 m) deposits of unconsolidated soil and rock material. Most soil series present have moderately high field capacities (approximately 20 cm H2O for the surface 1.3 m of soil) and rapid rates of saturated moisture movement. Percolation rates are typically greater than 12 cm/hr due to the large amount and size distribution of pore spaces (Rothacher et al. 1967). Stone content is the dominant factor causing variation in soil moisture storage capacity (Dyrness 1969). In ridgetop and steep-slope positions, soils are generally loam and clay loam derived from colluvium from reddish breccias and tuffs. Stone content ranges from 35 to 50%, generally increasing on south-facing slopes, and depth to weathered parent material is usually over 1 m. Soils derived from greenish breccias and tuffs are widely distributed. The surface and subsurface horizons are loam to clay loam with up to 50% gravel content by volume. Depth to parent material is 0.6 m to 1.2 m.
The H. J. Andrews Experimental Forest is underlain exclusively by bedrock of volcanic origin. Three geologic formations have been mapped for the HJA and correspond roughly with elevation (Swanson and James 1975). Little Butte Formation bedrock (< approximately 760 m elevation), dated as Oligocene to lower Miocene, consists of massive tuffs and breccias derived from mudflows and pyroclastic flows. Sardine Formation bedrock (760 m to 1200 m), dated as middle to late Micocene, consists of two units: a lower unit containing welded and non-welded ash flows (notably less altered than underlying Little Butte rocks of similar lithology), and an upper unit containing basalt and andesite lava flows. Andesitic and basaltic lava flows (>1200 m), termed "Pliocascade" Formation, were deposited during the Pliocene and overlie Sardine Formation material. Watersheds 1, 2, and 3 span the Little Butte-Sardine contact. Geology of these watersheds is roughly stratified by elevation. Bedrock of lower elevation areas of all three watersheds is dominated by reddish and buff-colored tuffs and breccias. At the mouth of Watershed 3, these rock types are buried under many feet of mixed colluvium exhibiting evidence of several periods of deposition. Sardine greenish tuffs and breccias dominate middle elevation bedrock in all three watersheds and extend to the ridge of Watershed 1. Associated with these rocks are numerous outcroppings of mainly basaltic flow rocks. In Watersheds 2 and 3, large portions of this bedrock are covered with a mantle (ó 20 m) of andesitic colluvium. Upper elevations in Watersheds 2 and 3 are underlain by deposits of Sardine andestic flow rock. In Watershed 1, this formation is limited to the extreme northeast corner. Most bedrock of this type is relatively unweathered with many rugged escarpments and outcroppings. Source: Swanson, F. and M. James. 1975. Geology and Geomorphology of the H. J. Andrews Experimental Forest, Western Cascades, Oregon. USDA Forest Service Research Paper. PNW-188. 14pp.
Gauged watershed area: 95.9 ha (original surveyed value used in rating equation calculations)
Prior to cutting in 1962-1966, Douglas-fir was the dominant species and ranged in age from about 100 to 500 years. Hemlock was intermixed in varying amounts and was generally younger. Other coniferous species present include western redcedar, locally abundant in drainages, and individual sugar pines scattered on ridgetops. Pacific yew is common in the understory. Hardwood species are common, but generally occur only in small amounts. In decreasing order they are: bigleaf maple, Pacific dogwood, golden chinkapin, and red alder. Six understory plant communities are present: 1) hazel-salal (10% of watershed area); 2) rhododendron-salal (10%); 3) vine maple-salal (10%); 4) vine maple-Oregon grape (25%); 5) gold-thread (25%); and 6) sword-fern (20%). Source: Rothacher, J., C. T. Dyrness, and R. Fredricksen. 1967. Hydrologic and Related Characteristics of Three Small Watersheds in the Oregon Cascades. USDA Forest Service Pacific Northwest Forest and Range Experiment Station. 54 pp.
Typically, snow begins falling in November with peak snow water equivalent storage estimated to occur in Feb-April. Mean annual maximum is about 375 mm water equiv. at highest elevation. Transient snow zone with 25% precip falling as snow at lowest elevations.