Term

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 


Term

Definition
the highest discharge that occurs in a rainfallrunoff event
the peak on a hydrograph 


Term

Definition
the portion of the hydrograph leading up to the peak flow 


Term
what is the falling limb? 

Definition
the portion of the hydrography following the peak flow 


Term

Definition
the discharge that the peak rises above, the background flow
it is supplied by groundwater from the catchment 


Term
what is storm flow and what supplies it? 

Definition
it is the rise in discharge during a storm
it is supplied by groundwaterand some combination of the flowpaths (HOF, SSSF, and SOF)



Term

Definition
the time delay between peak rainfall and the peak flow in the river 


Term
what is a floodplain? why is the definition important? 

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) 


Term

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 


Term
How can you construct a curve to show the probability of a perticular discharge occuring? 

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 


Term
what is the 100year flood? 

Definition
the flood that has a recurrence interval of 100 years 


Term
what is the probability of a particular flood happening in the coming year? 

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% 

