1. SEDIMENT DELIVERY FROM UNGAGED TRIBUTARIES TO THE COLORADO RIVER IN GRAND CANYON Robert H. Webb Peter G. Griffiths U.S. Geological Survey 1675 W. Anklam Road Tucson, AZ 85745 Theodore S. Melis Grand Canyon Monitoring and Research Center 2255 N. Gemini Drive Flagstaff, AZ 86001

3. DRAINAGE AREAS OF UNGAGED TRIBUTARIES IN GRAND CANYON

4. ESTIMATING STREAMFLOW SEDIMENT YIELD Use multiple techniques to constrain estimates: Regional sediment yield data; Empirical sediment yield relations; Flood-frequency rating-curve technique.

5. REGIONAL SEDIMENT YIELD DATA (mostly from east of Grand Canyon) Source AreaSediment loadSediment yield (km 2 )(10 6 Mg/yr)(Mg/yr/ km 2 ) 25 small reservoirs (Hains, et al. 1952) 0.2-47.1<0.0035.7-628 Moenkopi Wash #129.20.0069237 Yellow Water Wash #152.20.034643 Coal Mine Wash #177.10.019245 Yellow Water Wash #2109.10.017158 Coal Mine Wash #2112.70.009584 Paria River at Lees Ferry3,6503.0820 Moenkopi Wash, Tuba City4,2190.65155 Little Colorado River near Cameron68,6009.2130 Colorado River at Lees Ferry290,00065.220 Colorado River near Grand Canyon366,00084.230 RED NAMES indicate previously unused data from Black Mesa.

6. EMPIRICAL METHODS FOR ESTIMATING SEDIMENT YIELD Estimated Sediment yield SourceOriginal EquationUnits(10 6 Mg/yr)(Mg yr -1 km -2 ) Renard (1972) 0.001846 A -0.1187 ac-ft/ac/yr0.67204 Strand (1975)1130 A 0.77 m 3 /yr1.62494 Dendy and Bolton (1976)1280 Q 0.46 (1.43-0.26 log A)tons/mi 2 /yr0.81247 Flaxman (1972)log(Y+100) = 6.21301 - ac-ft/mi 2 /yr0.1442.6 2.19113 log (X 1 +100) + 0.06034 log (X 2 +100) - 0.01644 log (X 3 +100) + 0.04250 log (X 4 +100) Soil Conservation Svc. (1975)PSIAC methodac-ft/mi 2 /yr13.54,110 Howard and Dolan (1981)780 AMg/km 2 /yr2.56780 Randle and Pemberton (1987)1750 A -0.24 m 3 /km 2 /yr2.4731 Graf (1987)1200 A 1.0 m 3 /yr3.91,190 n = 219 ungaged tributaries

7. FLOOD FREQUENCY TECHNIQUE We combine: Sediment-rating curves from 5 small drainages on Black Mesa; Flood hydrographs for 22 summer and 20 winter flows above base discharge on Bright Angel Creek; Regional flood-frequency relations developed for Arizona (Roeske, 1978); Q s = Q 10 + 2. Q 5 + 5. Q 2

8. STREAMFLOW SEDIMENT-YIELD BY ALL THREE METHODS (r = 0.86)

9. STREAMFLOW SEDIMENT-YIELD ESTIMATES DrainageSediment yield (10 3 Mg/yr) Sediment-yield reachareaRegionalRenardFlood- (km 2 )dataequationfrequency A: Lake Powell – Paria R.321657645 B: Paria R. – LCR 2,953610593457 C: LCR – Bright Angel Cr.4949812782 D: Bright Angel – Kanab Cr.1,640332375240 E: Kanab – Havasu Cr.276576441 F: Havasu – Diamond Cr.3,958821779488 G: Diamond Cr. – Lake Mead3,236669633397 TOTAL12,8782,6502,6501,750

10. A DEBRIS-FLOW SEDIMENT-YIELD MODEL We combine: Frequency model based on logistic regression (Griffiths et al., 1996); Magnitude model based on monitoring of debris flows from 1984 through 1998 (Melis et al., 1994); Reworking of debris fans by Colorado River floods (Melis, 1997; Webb et al., 1997, 1999).

12. DEBRIS FLOW VOLUMES IN GRAND CANYON 100 1,000 10,000 100,000 0.11101001000 Debris-Flow Volumes V max = 11,808. A 0.294, R 2 = 0.89 V avg = 5728. A 0.278, R 2 = 0.47 Debris Flow Volume (m 3 ) Drainage Area (km 2 )

13. DEBRIS-FLOW SEDIMENT YIELD ESTIMATES ReachDrainage Area Sediment Yield (10 3 Mg/year) (km 2 )V max model V avg model A: Lake Powell – Paria R.321 0 * 0 * B: Paria R. – LCR 2,953 80, 38 C: LCR – Bright Angel Cr.494 3014 D: Bright Angel – Kanab Cr.1,640 5024 E: Kanab – Havasu Cr.276 53 F: Havasu – Diamond Cr.3,958 7234 G: Diamond Cr. – Lake Mead3,236 5828 TOTAL12,878 295141 * Tributaries in Reach A (Glen Canyon) do not produce debris flows.

14. COMBINED SEDIMENT YIELD (STREAMFLOW + DEBRIS FLOW) Sediment Yield Debris flow contribution Reach (10 3 Mg/year) (%) V max model V avg modelV max modelV avg model A: Lake Powell – Paria R 656500 B: Paria R. – LCR 691648126 C: LCR – Bright Angel Cr.1271122313 D: Bright Angel – Kanab Cr.381356137 E: Kanab – Havasu Cr. 06205994 F: Havasu – Diamond Cr. 89385584 G: Diamond Cr. – Lake Mead72869884 Total2,9472,793105

15. Sediment load Source(10 3 Mg/yr) Colorado River at Lee’s Ferry (pre-dam)65,000 Little Colorado River9,200 Paria River3,000 Moenkopi Wash2,700 Kanab Creek800 Moenkopi Wash700 Ungaged tributaries in Marble Canyon600 Ungaged tributaries in Glen Canyon70 SEDIMENT SOURCES TO THE COLORADO RIVER

16. SAND CONTENT OF STREAMFLOW SEDIMENT YIELD TributarySand (%)Reference General15Randle and Pemberton (1987) Little Colorado River0.7-22.6Garrett et al., 1993 1-50Rote et al., 1997 Bright Angel Creek87 *† Garrett et al., 1993 1-64Rote et al., 1997 Kanab Creek0.1-14.5Garrett et al., 1993 0-36Rote et al., 1997 Havasu Creek1-89Rote et al., 1997 National Canyon 81-99 *† Garrett et al., 1993 * Not a gaging station; miscellaneous tributary flow in 1983 (Garret et al., 1993). † Calculated from silt+clay % and assuming no particles >2 mm were transported.

17. PARTICLE-SIZE DISTRIBTION OF STREAMFLOW SAND

18. Drainage Area Sediment Yield Reach(km 2 )(10 3 Mg/year) MinimumMaximumAverage A: Lake Powell – Paria R 321 104930 B: Paria R. – LCR 2,953 93462288 C: LCR – Bright Angel Cr. 494 157547 D: Bright Angel – Kanab Cr. 1,640 51251156 E: Kanab – Havasu Cr. 276 94327 F: Havasu – Diamond Cr. 3,958 125619385 G: Diamond Cr. – Lake Mead 3,236 102505314 Total 12,878 4042,0021,247 SAND DELIVERED TO THE RIVER Following Debris Fan Reworking

19. CONCLUSIONS Ungaged tributaries in Grand Canyon deliver nearly 3. 10 6 Mg/yr of sediment to the Colorado River. This is comparable to the sediment load of a major tributary. As debris fans are reworked, an average of 1. 10 6 Mg/yr of sand is made available to the regulated river throughout Grand Canyon. In Glen and Marble Canyons, an average of 0.32. 10 6 Mg of sand is delivered to the river annually. This is: –20% of the sand supplied by the Paria River each year; –twice the sand estimated for this reach in the 1995 EIS. Debris flows contribute between 5 and 10% of total sediment, and no more than 8% of sand; but they deliver 100% of coarse sediment (boulders and cobbles) that create critical habitat and zones of fine sediment storage. Efforts are underway by the GCMRC to verify streamflow estimates by gaging several small drainages in Marble Canyon.