Geology 1330 Lecture 17 Flooding and Rivers (Complete)
Geology 1330 Lecture 17 Flooding and Rivers (Complete) GEOL 1330
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This 2 page Class Notes was uploaded by Julian Quesada on Sunday April 24, 2016. The Class Notes belongs to GEOL 1330 at University of Houston taught by Dr. Daniel Hauptvogel in Spring 2016. Since its upload, it has received 13 views. For similar materials see Physical Geology in Geology at University of Houston.
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Date Created: 04/24/16
GEOL 1330 LECTURE 17 - RIVERS AND FLOODING Hydrologic Cycle -Most precipitation that falls on land enters the soil (infiltration) or remains at the surface and moves downslope as runoff -Different areas of runoff that meet will form streams/rivers -Areas that provide the runoff are called drainage basins -Mississippi River drainage basin -Biggest drainage basin the US -Fed by man smaller rivers (tributaries) -Erosion of the hill slopes is the main source of fine sediment in rivers -Equal amounts of sediment are eroded and deposited in the zone of transportation -Sediment is deposited at the end of the river (mouth) Rivers -River flow is driven by gravity -Water always moves from higher elevation to lower elevation -Constantly in motion -Rivers are lazy -Rivers will take the path of least resistance -Factors that affect river flow velocity include: -Gradient - Slope of the Stream -Channel Shape and Size -Discharge - amount of water flowing (volume/unit time) -Two basic types of rivers -Braided - Steep gradient and/or high sediment load -Meandering - Shallow gradient -Meandering rivers have large bends (meanders) -Erosion occurs on the outside of the bend, deposition on the inside -Mississippi River wants to abandon the lowermost 300 miles of its channel and divert to the Atchafalaya -The Atchafalaya is an off shoot of the Mississippi River and is an a shorter and quicker route to the Gulf -The Army Corps of Engineers constructed a massive dam to prevent this from happening -Confining the Mississippi River has led to vanishing wetlands across southern Louisiana because sediment is not being replaced during flooding -River flooding, natural levees, and sediment deposition -Urbanization prevents infiltration, which causes an increase in runoff -Discharge - amount and rate of water flowing in a river -ft^3/s -A 100 year flood means that a flood of that size has a 1% chance of occurring each year Flooding Q: How can you reduce flooding without reducing the discharge (amount of water flowing)? A: Increase the Velocity of water in a channel -How? -Decrease resistance to flow -Increase channel efficiency -Straighten the river -Increase slope (defined as Y/X or vertical/horizontal) -By straightening the river, we decrease X and the river can empty out into the mouth faster
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