bullshit
hydrology
over time)
hyetograph hyenas are intense (intensity
:
flow (flowrate over time)
hydrograph hydro shows
:
,Manning's equation Q flowrate
=
:
coefficient
n =
Manning's roughness
sectional flow
Arg
A cross area
Q=
=
S =
longitudinal bed slope
Flood
Frequency Analysis :
AEP =
# in % where T :
return
period in
years
describes probability of design flow being exceeded and the
design
failing in
any one
year.
m :
rank of flood magnitude
PlottingPosition =
number of years
AEP n :
=
&
Plotting positions are estimates of the probability of a flood of a certain rank of
magnitude or
higher occuring in a
given year.
Probability of 1 in n year flood occuring in AEP =
any year
so
probability this NOT occuring is 1-I
"
Over a n year period the prob of this flood NOT
occuring
is (1-AEP)
1-(1-AEP)
n
prob of it
so
occuring is
PP =
P(XyXm) =004
PDF :
shows probability of X taking on certain values
Discrete PDF possible outcomes arranged in
groups
·
=
Continuous PDF : can fake on real number values
CDF : shows probability of X being at most that value Starts at O, ends at
·
Frequency Factor is a function of AEP and
M &X
general equation
+
X
departure from
: =
=
↑ r the mean
value of random
- mean of
variance
distribution
, Extreme Value Distributions :
Log Pearsons III Method :
the flood flow
Ry :
discharge for an AEP of y %
log (Qy) M kyS M the mean of the logs of the annual flood
+
·
= :
peak
flows from historical data
S : std of the logs of the peak annual flood flows
from historical data
Ky : a function of the
logs of the AEP and shew of data
f(x)
= Xi
:)
&
M
I
↑
S =
Em where N :
number of data points
E
3
skew :
g =
Log Pearsons 111 Steps -
1 find
.
logs of flow
magnitudes. find mean , sta , skew
2
. extract +
reproduce ky values for various AEPs
. find log Pearson Type
3 III flood flows for the various exceedance probabilities. Plot results with
original data
for AEP show flood flow value, and expected variability !
a
particular S
as a
Expected Variability :
-
Confidence Interval Envelope : calculate upper ,
lower limits of how flow value varies
from fitted function (expected discharge values) plot ,
on
graph
-
i -logio(Qy) KyS + M
=
↑
flow values for AEP
range of expected
3
hydrology
over time)
hyetograph hyenas are intense (intensity
:
flow (flowrate over time)
hydrograph hydro shows
:
,Manning's equation Q flowrate
=
:
coefficient
n =
Manning's roughness
sectional flow
Arg
A cross area
Q=
=
S =
longitudinal bed slope
Flood
Frequency Analysis :
AEP =
# in % where T :
return
period in
years
describes probability of design flow being exceeded and the
design
failing in
any one
year.
m :
rank of flood magnitude
PlottingPosition =
number of years
AEP n :
=
&
Plotting positions are estimates of the probability of a flood of a certain rank of
magnitude or
higher occuring in a
given year.
Probability of 1 in n year flood occuring in AEP =
any year
so
probability this NOT occuring is 1-I
"
Over a n year period the prob of this flood NOT
occuring
is (1-AEP)
1-(1-AEP)
n
prob of it
so
occuring is
PP =
P(XyXm) =004
PDF :
shows probability of X taking on certain values
Discrete PDF possible outcomes arranged in
groups
·
=
Continuous PDF : can fake on real number values
CDF : shows probability of X being at most that value Starts at O, ends at
·
Frequency Factor is a function of AEP and
M &X
general equation
+
X
departure from
: =
=
↑ r the mean
value of random
- mean of
variance
distribution
, Extreme Value Distributions :
Log Pearsons III Method :
the flood flow
Ry :
discharge for an AEP of y %
log (Qy) M kyS M the mean of the logs of the annual flood
+
·
= :
peak
flows from historical data
S : std of the logs of the peak annual flood flows
from historical data
Ky : a function of the
logs of the AEP and shew of data
f(x)
= Xi
:)
&
M
I
↑
S =
Em where N :
number of data points
E
3
skew :
g =
Log Pearsons 111 Steps -
1 find
.
logs of flow
magnitudes. find mean , sta , skew
2
. extract +
reproduce ky values for various AEPs
. find log Pearson Type
3 III flood flows for the various exceedance probabilities. Plot results with
original data
for AEP show flood flow value, and expected variability !
a
particular S
as a
Expected Variability :
-
Confidence Interval Envelope : calculate upper ,
lower limits of how flow value varies
from fitted function (expected discharge values) plot ,
on
graph
-
i -logio(Qy) KyS + M
=
↑
flow values for AEP
range of expected
3
