Chapter 6EntrenchedMeandersMeanders are a series of sinuous curves or - PDF document

Chapter 6EntrenchedMeandersMeanders are a series of sinuous curves or loops that are found in riveror streamhe distance around the inside of the meanderis less so the current there flows more slowly Figure 61.1. Diagram of an incised meander with steep undercut slope on the outside of the meander - off slop e on the inside of the meander. Contours are in hundreds of feet. When a meander cutsinto bedrock it is generally called an incised meanderThere are two types of incised meanders: 1) an ingrown meander which continues to grow horizontallyvertically, with an asymmetric slope in its walls igure and 2)an entrenched meander with symmetrical, nearvertical walls whichcutdownward with little if any horizontal growthEntrenchedor sometimes spelled intrenchedeanders have vertical walls on both sides of the channel, indicatingthere was once a rapid downward cutting without the formation of slipoff slopes on the inside of bendsunlikeincised meanders. The presence of slipoff slopes is indicative of an ingrown meander.MeandersareCommonMeanders seem to be mmon featureof watercourses. Today, theyform along rivers and streams, especially when the slope is low. alley meanders are unique sincethey indicateconsiderably larger amount of water formed the valley than what is flowingtoday(see hapter 62). The oosenecks on the San Juan River near Medicine Hat, southeastUtahigure 61.2) and Horseshoe Canyon on the Colorado River below Lake Powell, Arizona (Figure 61.3) are twofamous exampleof entrenched meanders. The first is especiallydifficult to explain usingpresent day processessinceit cuts throughthe Monument uplift of the Colorado Plateau.Neuendorf et al.. Ref. , p. 323.Neuendorf et al.. Ref. , p. 327.Neuendorf et al.. Ref. , p. 211. Figure 61.2. The Goosenecks of the San Juan River (photo courtesy of Jim Clarke).