Geomorphology and forest ecology of a mountain region in the central Appalachians

The area studied, mostly in the headwaters of the Shenandoah River, Augusta andi Rockingham Counties, Va. , includes about 55 square miles of densely forested mountain land and has an average relief of about 1,500 feet. It is part of an area that in June 1949 was subjected to a violent cloudburst which damaged large tracts on slopes and bottom lands. Most of the area is underlain by flaggy arkosic sandstone and interbedded reddish shale of the Hampshire formation of Devonian age. The highest ridges are capped by massive sandstone of the Pocono formation of Mississippian age. In most of the area the rocks dip gently to the southeast but in the northwestern and southeastern parts they are folded into synclines that localize northeastward-trending ridges. Topography is remarkably uniform and the slopes are graded to regular forms that may be described in simple mathematical terms. Because of a high bifurcation ratio between streams of different orders, almost half of the area is composed of firstorder valleys. Each of the first-order valleys may be subdivided! into five different parts based on the convexity or concavity of the contours. Each part, because of its geometric form, receives water downslope at a different rate. Tbe driest area on which the contours are convex outward (from the mountain) is called the "nose" and presumably receives the least moisture by flow from the slope above. The side slope has straight contours and hypothetically receives somewhat greater runoff. The hollow above the stream head is an area of concentration of the drainage lines in which the discharge of storm runoff is inferred to increase downslope at a rate greater than the square of the distance. It merges with the channelway, a narrow strip running down the valley axis between steep side slopes. In the channelway, runoff increases downstream in proportion to the 1.6 power of the distance. The channelway at some places is bordered by a narrow strip of concave-upward slope that because of its geometric form receives somewhat more runoff than the side slopes above. In valleys larger than the first and second order the channelway is so broad that the stream channel itself is bordered by bottom lands many times larger. All of the bottom lands are subject to erosion or deposition during floods of various frequencies. The stony and bouldery soils of the mountain slopes were sampled at many localities by measuring the diameters of individual particles selected at points on a gridi pattern. The mean size of the particles on the surface of the ground was found to vary markedly from one part of a valley to another and to increase roughly with the runoff concentration inferred from the topography. The texture of debris is fine on noses and coarse in channelways and hollows. Mean size ranges from *Johns Hopkins University, formerly of Harvard University. less than 1 mm on some noses to over 250 mm in some hollows. In the channelway the size generally decreases to about 100 mm and remains nearly constant in a downstream direction. Standard deviation or sorting of the particles narrows as drainage area increases. Fields of large, angular quartzite blocks are conspicuous features of some side slopes and noses. They generally are present where massive quartzitic sandstone of the Pocono formation crops out in an exposed location such as a ridge top or nose, and where the sandstone is underlain by relatively soft shale. In these places boulders have slid down, forming a mantle on