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 Theodore S. Melis Grand Canyon Monitoring and Research Center 2255 N. Gemini Drive Flagstaff, AZ 86001

DRAINAGE AREAS OF UNGAGED TRIBUTARIES IN GRAND CANYON

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

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) < Moenkopi Wash # Yellow Water Wash # Coal Mine Wash # Yellow Water Wash # Coal Mine Wash # Paria River at Lees Ferry3, Moenkopi Wash, Tuba City4, Little Colorado River near Cameron68, Colorado River at Lees Ferry290, Colorado River near Grand Canyon366, RED NAMES indicate previously unused data from Black Mesa.

EMPIRICAL METHODS FOR ESTIMATING SEDIMENT YIELD Estimated Sediment yield SourceOriginal EquationUnits(10 6 Mg/yr)(Mg yr -1 km -2 ) Renard (1972) A ac-ft/ac/yr Strand (1975)1130 A 0.77 m 3 /yr Dendy and Bolton (1976)1280 Q 0.46 ( log A)tons/mi 2 /yr Flaxman (1972)log(Y+100) = ac-ft/mi 2 /yr log (X ) log (X ) log (X ) log (X ) Soil Conservation Svc. (1975)PSIAC methodac-ft/mi 2 /yr13.54,110 Howard and Dolan (1981)780 AMg/km 2 /yr Randle and Pemberton (1987)1750 A m 3 /km 2 /yr Graf (1987)1200 A 1.0 m 3 /yr3.91,190 n = 219 ungaged tributaries

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 Q Q 2

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

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

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).

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

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 * 0 * B: Paria R. – LCR 2,953 80, 38 C: LCR – Bright Angel Cr D: Bright Angel – Kanab Cr.1, E: Kanab – Havasu Cr F: Havasu – Diamond Cr.3, G: Diamond Cr. – Lake Mead3, TOTAL12, * Tributaries in Reach A (Glen Canyon) do not produce debris flows.

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 B: Paria R. – LCR C: LCR – Bright Angel Cr D: Bright Angel – Kanab Cr E: Kanab – Havasu Cr F: Havasu – Diamond Cr G: Diamond Cr. – Lake Mead Total2,9472,793105

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

SAND CONTENT OF STREAMFLOW SEDIMENT YIELD TributarySand (%)Reference General15Randle and Pemberton (1987) Little Colorado River Garrett et al., Rote et al., 1997 Bright Angel Creek87 *† Garrett et al., Rote et al., 1997 Kanab Creek Garrett et al., Rote et al., 1997 Havasu Creek1-89Rote et al., 1997 National Canyon *† 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.

PARTICLE-SIZE DISTRIBTION OF STREAMFLOW SAND

Drainage Area Sediment Yield Reach(km 2 )(10 3 Mg/year) MinimumMaximumAverage A: Lake Powell – Paria R B: Paria R. – LCR 2, C: LCR – Bright Angel Cr D: Bright Angel – Kanab Cr. 1, E: Kanab – Havasu Cr F: Havasu – Diamond Cr. 3, G: Diamond Cr. – Lake Mead 3, Total 12, ,0021,247 SAND DELIVERED TO THE RIVER Following Debris Fan Reworking

CONCLUSIONS Ungaged tributaries in Grand Canyon deliver nearly 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 Mg/yr of sand is made available to the regulated river throughout Grand Canyon. In Glen and Marble Canyons, an average of 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.