HOOD RIVER-WHITE SALMON RIVER AREA. 21 



the stream courses. In the White Salmon River Valley there is 

 but little alluvial soil of recent formation, but along the Columbia 

 and Hood Rivers and the tributaries of the latter recent water-laid 

 soils occur in more or less extensive bodies. Overflow along the 

 Hood River and its tributaries is rare and the soil conditions are 

 stable and well defined, but a large part of the recent soils along the 

 Columbia River are overflowed annually and consequently are sub- 

 ject to more or less alteration from year to year. 



The soUs of the area surveyed thus fall into a number of more or 

 less distinct groups, according to their topographic position and 

 mode of formation. Each group is represented by one or more 

 soil series and each soil series consists of a number of soil types. 

 The latter, within each series, are similar in general characteristics 

 of color, character of subsoil or other underlying material, topog- 

 raphy, origin, and mode of formation, but differ in texture as deter- 

 mined by the relative proportions of the different grades of soil 

 material. A complete series consists of a number of associated and 

 closely related soil types ranging in texture from coarse in the 

 sandy members to fine in the silty and clay types. Some of the 

 soU series recognized in this area, however, are represented by but 

 a single soil type. 



The soil type is the unit of classification and each type encountered 

 is indicated in color on the soil map accompanying this report. 



The residual soils of the area, derived by weathering in place of 

 the underlying rock, are represented by three types — the loam and 

 stony loam members of the Underwood series and Rough stony land. 

 The Underwood soils occur on all of the hill and mountain slopes in 

 the area, and are by far the most extensively distributed soils in the 

 area. The surface soil of the loam type carries noticeable quantities 

 of small, reddish-brown pellets, formed by the cementing of the soil 

 particles by iron salts or by spherical weathering of fragments of 

 basaltic rock. These are locally known as red shot. The stony 

 loam contains large quantities of angular rock fragments in both the 

 soil and subsoil. The color of these soils is commonly a light brown 

 or light reddish brown, with occasional areas of grayish brown, par- 

 ticularly in the bodies adjacent to the White Salmon River Valley. 

 The larger part of the area occupied by these soils supports a heavy 

 growth of fir and pine, but in sections of restricted rainfall and of 

 steep slope and where the drainage is excessive or the soil somewhat 

 shallow these trees give way to scanty growths of oak, brush, and 

 grass. Rough stony land, a nonagricultural type, includes areas in 

 which the quantity of fragmental rock in the soil or of rock outcrop 

 is too great to allow cultivation. The soU is generally thin, the 

 topography is quite steep, much of it precipitous, and the forest 

 growth is usually a scattering stand of pine. 



