THE DRAINAGE DENSITY ENVELOPE.
IOWA STATE UNIV AMES SOIL RESEARCH LAB
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A conceptual model for the development of a drainage net by headward erosion is developed and described mathematically. The theoretical maximum stream length for any size basin is shown by plotting total stream length sum L versus the square root of basin area square root of A. An envelope line is fit for maximum skewness, giving the drainage density envelope sum L square root of A tan gamma - N sub 1 Xc, where tan gamma is the slope of the line, N sub 1 is the number of first order streams, and Xc is the critical distance. The influence of basin order, soil type, and climate on the envelope parameters is investigated theoretically and from preliminary map and field data. Secondly, growth model is proposed for the headward extension of a stream as a function of time Tc 1KWb ln XcL sub b where Tc is the time required to extend to the belt of no erosion, L sub b and W sub b are the length and width of the rectangular basin and K is a constant depending on the erodibility of the soil. The equation gave correct relative ages of drainage patterns on different age drift sheets in Iowa. Author
- Hydrology, Limnology and Potamology