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<br />CONTENTS
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<br />Page
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<br />Abstract ............... .........,..... ,........... ......,........, ...... ..................,........................................ ..........................., I
<br />Introduction......................... .................. ........,............ ....................,.......,.... ...... ............ ,......... ................,... 1
<br />Pwpose and scope ............,............................,......................,...,......,..................................................... 2
<br />Acknowledgements............, .................. .....,.. ...... .....................,..,..........,.................. ............,.............., 2
<br />Units and place names..........................,............................................................................................,... 4
<br />Previous Studies ......................... ......,........... ........ ...................,............. ,.. ................... ..............................., 4
<br />Definitions of flow types that occur in Grand Canyon tributaries ,....,....................,.........................,.., 4
<br />Magnitude and frequency of debris flows........................,.........................................,....................,...., 5
<br />Tributaries and reaches of the Colorado River in Grand Canyon..............,.............,....,.............,............... 6
<br />Definition of geomorphically significant tributaries ..,...,...,..................................,.........................,..,.. 6
<br />Designation of reaches of the Colorado River ..................,......,..........................................................., 6
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<br />Drainage areas of ungaged tributaries ..,.....,.........,.......,......,.........................,..,..........................,......... 7
<br />Climatic variability in the Grand Canyon ........,...................,..,............,...................................................... 7
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<br />Streamflow sediment yield................... ......,...... ,....... ........ .............,........,.....,................. ...............,.... ,....... 9
<br />Regional sediment-yield data..... .................. ....,....,....,.............. .................., ..................... .................... 10
<br />Empirical sediment-yield relations.. ...... ......,........ .............., ........,....... ,........... ,... ........,. ....,...... ,.. .......... 12
<br />The flood frequency, rating-curve technique.............................................,...,.........................,......,..,.. 15
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<br />Regional flood frequency ........,...................................,.....,........................................,..............,...., 15
<br />Flood volumes and sediment-rating curves..,........................,.......,.........................,..............,..,...., 16
<br />Calculations of sediment yield ...........................,...........,..............................,.....,.........................,. 18
<br />Particle-size distribution of streamflow sediment .......................,...,.....,.............................................., 19
<br />Frequency of historical debris flows in Grand Canyon ............,...........................,........................,......,...., 21
<br />Evidence of historical debris flows .......................................................,.............................................., 21
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<br />Direct observations... ........ ,... ................................... ............, ....,...,.............. ..,.. ...................... ,.. ...... 21
<br />Photography.................... ........,.. ,...... ......... ........, ....,............ .................., .....,......... ....... ............,...... 22
<br />Temporal and spatial distribution of debris flows.......................,...............................,......................... 23
<br />Climatic variability and debris-flow initiation ................,...,.......,......,..............,....,............................., 23
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<br />Debris-/low sediment yield .....................................................,........................................,.......................,.. 24
<br />Debris-now frequency.... .................. .............. ...... ................ ....,..................... .................,...... .............., 24
<br />Debris-/low volumes ......,.. ....,.... ..........................,................. ........, ...................... ...................., ....,...,.. 28
<br />Estimation techniques..... ......,.. ....,.. ........,. .... ................................ .......................,... ,.... ................... 28
<br />Volumes of debris /lows...........................,........ ..,.. ................................. ,......... .....................,... ,..... 29
<br />Particle-size distributions of debris /lows ....,.....,...................................................,..,............................ 29
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<br />Point counts .. ..................,........... ................. ..,. ....................... ................,.... ,.... ....,.......................... 30
<br />Pit excavations ...................... ...................,......................................... ..........,..... ,.. .......... ................. 30
<br />Dry-sieve analysis............. .............. ........,..... ...................... ....,.. ............... ........,...... ,........ ............... 30
<br />Particle-size distributions of debris /lows ................,....,............,..,......,....................,............,......... 31
<br />Bulk density of debris /lows ..............,.....,............................,...................................................,...... 3 I
<br />Reworking of debris fans by the Colorado River ....,.......................................................................,..... 32
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<br />Sediment-yield model........... ..........,......................... ..........,..,......,... ........................... ......,.... ............,.. 33
<br />Total sediment yield of un gaged tributaries ................................,..,..,......................................................... 33
<br />Climatic variability and stream/low sediment yield..........,...............................,...................,..................... 34
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<br />Discussion and conclusions ........... ......,......,..... ,...... ,.. .............., ............................. ,.... .......................... ,..., 35
<br />References Cited... ........................... ......,.............,., ...........,..,................... ........,........... ,................. ......,..... 38
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<br />Conten" III
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