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<br /> <br />Housing development and drainage alterations caused this <br />accelerated erosion near Golden. <br /> <br />Aggravating Circumstances <br /> <br />~an's activities greatly influence the rate and extent of <br />erosion and deposition. Stripping the land surface of <br />vegetation, altering natural drainages, and rearranging the <br />earth through construction of highways, subdivision <br />days I opment, farm I and preparat I on, and mod I f i cat i on of <br />drainage channels for water control projects are significant <br /> <br /> <br />factors In increased eras! on and depos I t I on. A II the <br />geo I og I c processes wh i ch make ava II ab I e more mater I a I for <br />erosion and deposition tend to increase the rates of each <br />process. This is particularly true for landsl ides, mudflows, <br />debris flows, earthflows, rockfalls, and physical ano. <br />chemical weathering. These processes also Involve erosion <br />and deposition whl Ie frequently making more materIal <br />vulnerable to erosion. <br /> <br />Mitigation <br /> <br />The processes of erosion and deposition cannot be stopped <br />tota II y. They can be reduced and contro II ad by surface <br />drainage management, revegetation of disturbed lands, <br />contro III ng stream-carr i ed eroded mater 1 a Is in sed i ment <br />catchment basins, and riprapplng of erosion-prone stream <br />banks, espec I a II y adjacent to structures. Understand i n9 <br />these processes and taking preventative action can lead to <br />development and land-use methods which minimize losses. <br /> <br />Land Use <br /> <br />urdinarJly, erosion and deposition do not curtai I land use, <br />especially if efforts are made to minimize them. <br /> <br />Case History <br /> <br />Near Larkspur in Doug 1 as County an access road and sha II ow <br />borrow ditch were cut to serve an airport runway uphi II from <br />the access road. During construction of the road and borrow <br />pit a large area was stripped of vegetation. Heavy water <br />runoff from above the runway and the runway itsel f was <br />channelled down the borrow ditch. There were no control <br />features to slow the velocity of the water or retard erosion. <br />!lithln five years the borrow ditch was eight feet deep. <br />Properly designed and Installed water control structures, <br />revegetation of the graded area, detention ponds, drop <br />structures, and other measures would have paid for themselves <br />in later maintenance and repair costs. <br /> <br />13 <br />