Term
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Definition
a record of discharge in a river over time
most attention is paied to the peaks on a hydrograph - these are generally associated with rainstorms or snwomeld events |
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Term
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Definition
the highest discharge that occurs in a rainfall-runoff event
the peak on a hydrograph |
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Term
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Definition
| the portion of the hydrograph leading up to the peak flow |
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Term
| what is the falling limb? |
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Definition
| the portion of the hydrography following the peak flow |
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Term
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Definition
the discharge that the peak rises above, the background flow
it is supplied by groundwater from the catchment |
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Term
| what is storm flow and what supplies it? |
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Definition
it is the rise in discharge during a storm
it is supplied by groundwaterand some combination of the flowpaths (HOF, SSSF, and SOF)
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Term
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Definition
| the time delay between peak rainfall and the peak flow in the river |
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Term
| what is a floodplain? why is the definition important? |
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Definition
the flat area adjacent to the river channel, constructed by the present river in the present climate and frequently subject to overthrow
(definition from Luna Leopold, important b/c stresses the fact that rivers normally overtop their banks and flow on the adjacent floodplain) |
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Term
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Definition
if it is defined as flow outside the channel, then floods are a regular, frequent occurence in the landscape that happen when the flow is high enough to push the river out of its banks
to quantify the flood risk for a certain area/find where flood risk is low need to understand teh frequency and magnetude of high flows |
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Term
| How can you construct a curve to show the probability of a perticular discharge occuring? |
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Definition
1. record the highest discharge each year for n years (or obtain the records for a location)
2. rank these annual floods according to discharge, with the largest discharge assigned rank 1, the second rank 2 etc
3. compute the recurrence interval for each flood. using:
RI=(n+1)/m
where RI is recurrence interval, n is the number of years in the record, and m is the rank of the flood
4. plot the discharge versus the recurrence interval using logarithmic graph paper |
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Term
| what is the 100-year flood? |
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Definition
| the flood that has a recurrence interval of 100 years |
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Term
| what is the probability of a particular flood happening in the coming year? |
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Definition
the reciprocal the recurrence interval:
P=(1/RI)x100%
(the 100 year flood or RI=100 has a 1% probability of happening in any year while the 10 year flood has a 10% probability and the 2 year flood has a 50% chance)
if the 100 year flood happens this year, the probability is 1% and if it happens next year the probability is still 1% |
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