Laserfiche WebLink
<br />suggesting that debris flo'is arE! not as common near the downstream ends <br /> <br />of the basins. <br /> <br />Debris flows and othel" mas~i-transport processes characteristically <br /> <br />result in deposits or large quantities of debris in the channels, ranging <br /> <br />in size from mud to large boulders. These channel "lag deposits", which <br /> <br />have been deposited in each of the three basins studied, are susceptible <br /> <br />to remobilization during future events. They also contribute significantly <br /> <br />to the future susceptibilities of the basins. <br /> <br />An additional indicator of future basin susceptibility to flows 15 <br /> <br />the ratio of debris removed during the last: events to the amount of debris <br /> <br />available ~n the basins. Unfortunately it was not possible to accurately <br /> <br />estimate the volume removed during the last storm. <br /> <br />Consequently, only <br /> <br />a rough estimate can be made by inspection of the basins. <br /> <br />HO~.vever, it <br /> <br />does appear that no more than 5 to 10 percent was removed during the July <br /> <br />1977 event; thus 10 to 20 mJre e~ents of a similar magnitude are possible <br /> <br />even if no more unconsolidated debris aceumul,ates on the steep slopes through <br /> <br />the weathering and mass-~'asting processes. <br /> <br />D. Summary Statement About the De:bris-Flow Basins <br /> <br />The presence of typical debris-fan landforms below the basins (the <br /> <br />area on which the houses are built) i_ndicates that debris flows have occurred <br /> <br />for a long period of time. Study of the basins suggests that the potential <br /> <br />- 12 - <br />