Question

Problem 5 The following data are annual maximum floods Q (in m/s) for 7 years of record from 2005-2011. Using frequent factor method (parametric analysis), determine the 200-year flow assuming that the flows follow (a) log-normal distribution and (b) Log-Pearson Type III distribution YEAR 2005 2006 2007 2008 2009 2010 2011 Q (m/s) 2400 3093 1680 2640 3787 3360 3413

Answer 1

Answer:-

Given That:-

The following data are annual maximum floods Q (in m/s) for 7 years of record from 2005-2011. Using frequent factor method (parametric analysis), determine the 200-year flow assuming that the flows follow

(a) log-normal distribution and

Log - Normal distribution is the special case of the log-[earson distribution in which

Cs

so from following data we get

= 3.450754

0.= 0.1204

K2 (when Cs = 0) = 2.576

2200 2 + Κοσ.

2200 3.7609044

X 200 = Antilog( 2200

X 200 5766.4m/sec

(b) Log-Pearson Type III distribution

YEAR	FLOOD, X(m3/sec)	Z = LOGX	Z-MEAN	(Z - MEAN)
2005	2400	3.380211	-0.070542758	0.004976281
2006	3093	3.49038	0.03962592	0.001570214
2007	1680	3.225309	-0.225444718	0.050825321
2008	2640	3.421604	-0.029150073	0.000849727
2009	3787	3.578295	0.127541305	0.016266785
2010	3360	3.526339	0.075585277	0.005713134
2011	3413	3.533136	0.082382288	0.006786841
			Σ(Z - MEAN) =	0.086988302
	MEAN =	3.450754

FROM THIS TABLE WE DETERMINE $\sigma _z$

$\sigma _z$ = 0.1204

C, = ΝΣ(2 – ) (N – 1)(N – 2)σ3

C = -1.1644

From Log-pearson Type iii distributiom

K2 1.201

2200 2 + Κοσ.

܀ [00 3.5954

X 200 = Antilog( 2200

X200 3939.13m/sec

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