Laserfiche WebLink
<br />A method to study the stability and movement of individual particles <br />(stones) comprising the rip rap layer was developed for the Sacramento River at <br />site E-IO near Chico, California. by painting a red stripe along the top "face of <br />the riprap layer during the low flo~ season (fig. 5). Any movement 01: indivi~- <br />ual stones was noted following flood events. The initial failnre by particle <br />erosion in February 1983 is illustrated in figure 6. At the time of the photo- <br />graph, the red stripe had been destroyed in the area shown but was stili visibie <br />near the upper end of the rod. Following a number of flooo >oVents betWeen <br />February and May 1983 during which the entire bank and rip-rap was .subject -r.o <br />inundation, particle erosion progressed to the condition shown in ~igure 7. All <br />but the largest stones were subsequently transported from the eroded area. <br /> <br />The scarp at the upslope end of the failure (fig. 6) is not related to a <br />slump failure as described by Schuster and Krizek (J 978). A slump is a mass <br />movement of material along a slip surface with the terminus of the upslope face <br />of the failure designated a scarp. The scarp observed with failures caused by <br />particle erosion is related to angular impingement of flow. Progressive SCour <br />during eddy action of the streamflow at flow expansions also tends to erode the <br />exposed bank after the protective layer of rip rap has been damaged. Du-ring the <br />initial stages of failure related to particle erosion, the height of the scarp <br />face is small. <br /> <br /> <br />Level rod <br />at top of ban k <br />~ <br /> <br />Steel fencepost <br /> <br /> <br />Displaced <br />- rock <br /> <br />FIGURE 5. Riprap on left bank of Sacramento River at E-lO near <br />Chico, California. A reference line shows location of stones in <br />December 1981. Flow is from left to right. Note displaced stone <br />near steel fencepost (photographed March 4, 1982\. <br /> <br />12 <br />