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EPHEMERAL STRE,ulS 27 .52 I . " . ]I 17 " .33 . 47 I 19 dsn<>;o--08 5 . 20 2 . .10 .05 I;; ~ ~ ~ ~. .01 N " Z < '" ~ ,005 .001 05 .1 .5 10 DISCHARGE. IN CUBIC FEET PER SECOND 50 500 5000 100 1000 Fl()tlRE 23.-Downstream change of median size 01 bed particles with discharge, ephemeral streams ne.ar Santa Fe, ~. :'\:[ex. Discharge dllterminedfrom discharge-Qrder relation, solid Hue, figure:?Xl. Number beside point is location serial number in appendixes A to D. by point 1. All these streams had only a small decrease of particle size downstrearu, and if particle size alone controlled roughness, point 1 would be expected to fall near the line y=O (constant roughness), That the data indicate some downstream decrease of roughness (y~ --0.12) presumably indicates that in addition to the slight downstream increase in particle size, there is also some effect of bed configuration. Possibly also width-depth ratio itself tends to influence channel resistance. The manner in which the analysis given above veri- fies and integrates previous work of Leopold and Mad- dock (1953) and Hack (1955) can now be seen. In figure 24 the relation between stream gradicnt and drainage area is presented for a selected set of strelims in the United States, including both ephemeral and perennial streams representing both eastern and western conditions. The two examples from Hack are for two eastern streams having different rates of change of bed-material size. In Calfpasture River the size of bed material is constant downstream; in Gillis Falls Branch the size of bed material increases downstream. Comparison of the graph for cphemeral streams with those for Calfpasture River and Gillis Falls Branch would lead one to surmise that the New Mexico stream" have an increase in particle size in the downstream di- rection. However, our measurements showed that particle size tended to decrease slightly downstream. JR'llo'ntr1lohlfil~ It ~~~_'k/~mm) -..-.......- .... 8 .l ~ '" ~ ~ ~ ~ ~ ~ '!; "' 9.01 ~ o_~ [ [ptemt-,.lchlnrJelsin~Me>ica. /'1'''11l;leSllllbooll;:lllSliflldowAsl<lllm 00----::--- I o 0-0_ o _ co 'f ......... --0 -- ,......... _0 ,001 ,001 ,01 DRAINAGE AREA, IN SQUARE MilES ,I 10 100 1000 ..m (~ll11lt1Jr!RM,.Vi'Ji'i" X ""-...( fD~~~r::rftH~SOW!l5treo'" 0', 0.0- ", I 0 0 ,0 _00_0 Glllisrll~Bn>id'1.Ma~rJJ."'J........y" ....,lI'.. x~............ x x I IlIrti<:leSI1eI'Cl'IlSIIl&dowos/ream ,.... ""'" IOItl frDmJ.T. Had) .."'...... .......... 00 FlGt:'RE 24.-Downstream change of stream gradient in selected drainage bll.Sins.