levees artificial levees prevent floods usually made with fine-grained sediments that are easily...
TRANSCRIPT
Levees
• Artificial levees prevent floods
• Usually made with fine-grained sediments that are easily eroded in floods
• Higher-quality levees mix coarse gravel or face with riprap to resist erosion
Flash floods are common in deserts
• Time is < 6 hours• Water is not absorbed• >50% fatalities occur in vehicles• Slot canyons are bad for hikers• Can occur via dam failure
– Natural dams (ice, quake)– Constructed dams
• Levee reduces width of flood-flow part of river and raises water level during flooding
• Levees act to:– Eliminate storage of
floodplain– Constrict flow and raise
upstream water levels– Increase flood levels
upstream and downstream
Unintended Consequences of Levees