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| is used by FEMA to establish regulations for building near streams. A 100 year flood has a 1 percent chance of happening in any single year, although it also has a one percent chance of happening in the year following a similar magnitude event |
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| implies the transport of loose sediment fragments and fan refers to the shape of the deposit in map view |
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| is the level at which the water spills over the banks. |
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| when the stream will reach a lake or the ocean it reaches a base level below which the stream cannot erode |
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| the sediment carried along the steam bottom |
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| develops when streams erode down to resistant bedrock |
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| not common, form end members of rivers that exhibit a complete range of behavior |
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| the depth of sediment eroded during floods, affects the shape of the stream channel distribution of sediment. |
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| when a flood is more than 47 percent sediment. it is concentrated enough that you could scoop it with a shovel. |
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| the delta is like tan alluvial fan except that the delta sediments are deposited underwater |
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| the total volume of water flowing per unit of time, is the average water velocity multiplied bu the cross sectional area of the stream |
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| in which the inflow and outflow of sediment is in balance |
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| comes on suddenly with little warning, water levels rise rapidly |
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| where the flood reaches its peak discharge and then falls more gently |
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| at high water the flooding river spills out of its channel and over that broad area |
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| the rate at which water flows from groundwater into a stream depends upon both the slope of the water table and the ease of flow though the water saturated sediments or rocks |
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Definition
| lake water may float the glacial ice damn, leading to rapid failure and flooding downstream |
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| a stream that is able to maintain this equilibrium |
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| is the steepness with which it descends from its highest elevation to its lowest, typically expressed in meters per kilometer |
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| to represent intensity of flooding as a plot of the volume of water flowing in a stream over a period of time |
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| a mudflow of volcanic material |
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| the volume of sediment a stream can carry |
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| lose water into the ground and often dry up between storms |
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| which sweep from side to side in wide turns called meanders |
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| if mud or clay dominates the solids in a flowing mass |
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Definition
| as water velocity slows at the edge of the deeper channel, sediment deposits to form a natural levee |
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| heavy precipitation can overwhelm the near surface permeability of soils, leading to rapid runoff over the surface |
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| uses the physical evidence of past floods that are preserved in the geologic record to reconstruct the approximate magnitude and frequency of major floods in order to extend the record further into the past and to recognize larger floods |
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| sediment is deposited as a point bar downstream in the slow water along the inside corner of the bend |
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| the average time between floods of a given size |
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| the number of tributaries of a stream, which has a significant effect on the rate of rise of floodwater's during and following a storm |
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Definition
| during torrential rainfall, some may flow across the ground as surface runoff directly into streams |
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Term
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Definition
| streams accumulate surface water from their watershed (drainage basin) |
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