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<br />FIGURES Page
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<br />1. Map of the Colorado River between Lake Powell and Mead reservoirs.................,........,.......,..,... 3
<br />2, Graph showing the drainage areas ofungaged Grand Canyon tributaries ...........,....,..,..............,... 8
<br />3, Graph showing standardized annual precipitation for the Grand Canyon region ,.....,..............,..... 10
<br />4, Graph showing standardized seasonal precipitation for the Grand Canyon region ..,......,...,....,...., II
<br />5. Graph showing standardized average decadal precipitation for the Grand Canyon region ............ 12
<br />6. Graph showing sediment-yield data from small reservoirs and gaging stations
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<br />on the Colorado Plateau................................................ .................. .....................,......,............. ,...... 12
<br />7. Graph showing estimates of streamflow sediment yield from empirical equations
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<br />and regional dala,............ ............ .................. .................................. ,..................... ............,............. 13
<br />8, Graph sbowing streamflow sediment-yield estimates for 768 Grand Canyon tributaries
<br />calculated using the regional flood-frequency estimates of Thomas and others (1997) ....,............ 18
<br />8, Graph showing streamflow sediment-yield estimates for 768 Grand Canyon tributaries
<br />calculated using the regional flood-frequency estimates of Roeske (1978) ................................... 19
<br />10, Graph showing particle-size distribution of sand delivered by streamflow from
<br />ungaged tributaries in Grand Canyon..........,.............,...............................,...................................., 21
<br />11. Map ofgeograpbic distribution ofbistorical debris flows (1872-1999) in Grand Canyon.......,..... 26
<br />12, Grapb sbowing distribution of debris-flow frequency factors for 736 ungaged tributaries ............ 29
<br />13, Graph sbowing the relation of tributary drainage area to debris-flow volume for
<br />30 bistorical debris flows in Grand Canyon ........................,..................,...........................,..........., 30
<br />14, Grapb sbowing particle-size distributions of 41 historical debris flows in Grand Canyon ..,......... 32
<br />15, Graph showing estimated time series of streamflow sediment yields in Reaches A and B
<br />based on climatic variability ...................,...................................................................................,... 37
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<br />TABLES
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<br />1. Geomorphic and sediment yield reaches of the Colorado River in Grand Canyon ,........,.............. 7
<br />2, Drainage areas ofungaged tributaries of the Colorado River between Glen Canyon
<br />Dam and Upper Lake Mead reservoir, Arizona .............................................................................. 8
<br />3, Characteristics of weather stations in the Grand Canyon region...................................,..............,.. 9
<br />4, Measured sediment loads at gaging slations..,...............................,......,.......,.....................,..,......... 13
<br />5, Estimates of sediment contribution by streamflow from 219 ungaged tributaries............,...........,. 14
<br />6. Estimated annual streamflow sediment yield from ungaged tributaries of the Colorado River..,... 15
<br />7, Regional regression equations for streamflow flood frequency...................,................................., 16
<br />8, Sediment rating curves for Bright Angel Creek and at five gaging stations on Black Mesa,........, 17
<br />9, Linear regression between peak discharge and sediment yield for 42 floods in Bright
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<br />Angel Creek .......................... ........................... ......................................... ...............,... ...........,.. ,...., 17
<br />10, Annual streamflow sediment yield from ungaged tributaries of the Colorado River ....,................ 19
<br />11, Estimated or measured sand content of streamflow entering the Colorado River ,......................... 20
<br />12, Sand delivery by streamflow from ungaged tributaries of the Colorado River in Grand Canyon.. 20
<br />13. Reach-averaged particle-size distribution of sand delivered by streamflow from ungaged
<br />tributaries of the Colorado River in Grand Canyon .................................................,......,....,.......,.. 22
<br />14. Debris flows that have significantly changed debris fans and rapids during the last century
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<br />in Grand Canyon........... ,..,....,.... ...... .........,., ........ ........ ..,........ ,....... .......... ...... .......................... ....,.. 24
<br />15, Model for frequency of debris flow occurrence in tributaries of the Colorado River..................,.. 28
<br />16, Percentage of boulders, cobbles, pebbles, sand, and silt+clay in debris flow........,...............,..,...., 31
<br />17, Annual sediment yield and sand delivery by debris flow in Grand Canyon .............................,..... 34
<br />18. Total sediment yield and sand delivery from ungaged tributaries of the Colorado River ,............. 36
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<br />IV Conten..
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