EARTHSC 2GG3 Lecture 33: Lecture 33 Floods and Human Interactions
6 May 2016
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Force of water against car can wash it downstream. Deep erosion may not be visible underwater. Difficult to escape from submerged and sinking car. Picture: even shallow floodwaters can lift a vehicle and wash it downstream. Image: hydraulic mining in yuba county, california, 1870. Bridges: raise roadway above 100-year flood level, partial dam across floodplain, with narrow open channel under roadway bridge. Without a bridge the river spreads over its floodplain during a flood (shown a left). Image: a sandbagged levee in fargo, north dakota. Courtesy of usgs: levee breach can lead to avulsion: redirection of main channel through breach, into lower path from which river can not escape, failures can also occur from: Bank erosion from river currents or waves. Piping or seepage through levee, sometimes reaching surface as sand boil: every time a levee is built, also reduces width of flood-flow part of river and raises water level during flooding, levees act to:
