
INTRODUCTION
MAXIMUM WATER LEVEL IN BAGMATI
OBSERVATION IN BURHI GANDAK
CORRELATIONS IN BURHI GANDAK
LAG TIME ANALYSIS IN BURHI GANDAK
OBSERVATION IN BAGMATI
FREQUENCY ANALYSIS IN BAGMATI
CORRELATION ANALYSIS IN BAGMATI
LAG TIME ANALYSIS IN BAGMATI
Introduction:
Floods are complicated natural events. It depends on several parameters, so it is very difficult to model analytically. The floods in a catchment depends on the characteristics of the catchment, rainfall and antecedent conditions. So the estimation of the flood peak is a very complex problem. There is several alternative methods to estimate the magnitude of a flood peak:
 Rational method
 Empirical methods
 Unit –hydrograph technique and
 Flood frequency method
Flood frequency method is a statistical method .The value of the annual maximum flood from a catchment area for large number of successive years is called the annual series.These data are then arranged in decreasing order of magnitude.
Then the probability of each event being equalled to or exceeded is calculated as:
P= m/N+1
Where m=order number of the event and
N=total number of events
Then the recurrence interval also called return period or frequency is calculated as
T= 1/P
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Maximum Water Level in Bagmati
Maximum W.L in JUNE 
YEARS 
HAYAGHAT
DL  45.72 
BENIBAD
DL  48.68 
1993 
41.81 
47.26 
1994 
41.71 
47.96 
1995 
42.75 
48.24 
1996 
41.99 
47.92 
1997 
40.55 
48.68 
1998 
41.20 
49.52 
1999 
43.65 
49.15 
2000 
43.83 
48.78 
2001 
43.30 
48.50 
2002 
41.45 
48.17 
2003 
44.64 
48.91 
2004 
42.00 
48.28 
2005 
39.94 
47.94 
2006 
41.51 
48.76 
Maximum W.L in August 
Years 
BENIBAD
DL  48.68 
HAYAGHAT
DL  45.72 
1991 
48.59 
44.42 
1992 
47.88 
45.02 
1993 
48.99 
46.27 
1994 
48.89 
44.47 
1995 
49.13 
45.53 
1996 
49.19 
46.25 
1997 
49.41 
46.68 
1998 
49.42 
47.82 
1999 
49.52 
47.50 
2000 
49.57 
46.89 
2001 
49.72 
46.30 
2002 
49.60 
47.83 
2003 
49.35 
45.84 
2004 
48.68 
45.72 
2005 
49.74 
46.76 
2006 
49.17 
43.31 
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OBSERVATION IN BURHI GANDAK
From year 1991 to 2006 i .e(16 years) monthly observation has been done during flood season. There is no flood in the month of June during past 16 years. Years of flood has been shown in the table below
Years of Flood 
MONTH 
LALBEGHIAGHAT 
SIKANDERPUR 
SAMASTIPUR 
ROSERA 
KHAGARIA 
JUNE 
W.L<D.L 
W.L<D.L 
W.L<D.L 
W.L<D.L 
W.L<D.L 
JULY 
1998,02,03,04 
1993,1998,02,
03, 04 
93,96,02,03,
04,98,99, 
93,96,98,
99,02,03,
04,06 
2000,01 
AUGUST 
1998,01,05, 
93,98,99,01,
02,03,05 
93,,95,,96,98,
99,01,02,03,
04,05 
91,94,96,
98,99,01,
03,05,06 
91,94,96,
98,99,01,
03,05,06 
SEPTEMBER 
1994,01,05 
94,98,99,
01,05 
93,94,96,98,99,
01,03,05 
93,94,98,
99,01,03,05 
91,92,93,
94,95,96,
98,99,01,
03,05 
OCTOBER 
W.L<D.L 
W.L<D.L 
2001 
94,01, 
2003 
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CORRELATIONS IN BURHI GANDAK :
Sl .No. 
BETWEEN 
CORRELATIONS 
1 
W.L at LAL.&SIK. 
0.83 
2 
W.L at SIK&SAMS. 
0.91 
3 
W.L at SAM&ROS. 
0.988 
4 
W.L at ROS.& KHAGARIA 
0.24 
5 
R.F at SIK&SAMS 
0.80 
6 
R.F at SAM&ROS. 
0.62 
7 
R.F at ROS.& KHAGARIA 
0.84 
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LAG TIME ANALYSIS IN BURHI GANDAK : 
Water level curves shows that the lagging time between different sites are as follows:
S.No 
Between 
LAG Time 
1. 
Lalbeghiaghat and Sikanderpur 
36 HOURS 
2. 
Sikanderpur and Samastipur 
16 HOURS 
3. 
Samastipur and Rosera 
16 HOURS 
4. 
Rosera and Khagaria 
24 HOURS 
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OBSERVATION IN BAGMATI: 
The study shows that during past 14years water level has exceeded the danger level in year 1998,1999, 2000, 2003 and 2006 only in the month of June at Benibad. But at Hayaghat it remains below the danger level in the month of june from 1993 to 2006.
Water level has exceeded the danger level in most of the year from 1993 to 2006 in the month of July.
Past 14 years analysis shows that at Benibad water level always exceeded the danger level in the month of August. But at Hayaghat water level remains below the danger level in August 2006, However it always crossed the Danger Level in past 10 years in the month of August.
During past 14 years the Water Level crossed the danger level in the month of September at Benibad for most of the years.
The maximum Water Level trend in the month of October during past 14 years shows that in this year there is record Water Level as 49.54m at Bendibad and 46.34m at Hayaghat. During past 14 years water Level had never crossed the Danger Level at Hayaghat, but in this year it crossed the Danger Level in October.
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Frequency Analysis in Bagmati :
June.
The maximum Water Level at Benibad in the month of june2006 is 48.76m which has return period of 3 years and whose probability was 0.33.
Frequency analysis gives the idea that the Water Level in the month of June will cross the Danger Level (48.68 m) having return period of 2.5 years with probability of 0.4.
July.
The maximum Water Level at Benibad in the month of July 2006 is 49.39m which has return period of 3.4 years and whose probability is 0.29.
Frequency analysis gives an idea that the Water Level in the month of July at Benibad will cross the danger level (48.68m) having return period of 1.25 years whose probability is 0.80.
August
The maximum Water Level at Benibad is the month of August2006 is 49.17m which has return period of 1.7 years and whose probability is 0.59. According to frequency analysis the Water Level in the month of August of Benibad will cross the danger level having return period of 1.2 years with probability 0.82.
September
The maximum Water Level at Benibad in the month of September2006 is 49.66m, which has return period of 17 years with probability 0.06.
According to frequency analysis the Water Level in the month of September at Benibad will cross the danger level having return period of 1.20 years with probability 0.80
October.
The maximum water level at Benibad in the month of October2006 is 49.54m which has return period of 15 years with probability 0.07.
According to frequency analysis the Water Level in the month of October at Benibad will cross the danger level having return period of 1.5 years with probability 0.67.
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Correlation Analysis in Bagmati :
Correlation analysis has been done by arranging all data in the column. The correlation coefficients has been obtained as follows:
Sl. No. 
Correlation Between 
June06 
July06 
Aug06 
Sept06 
Oct06 
1 
W.L. at Dubbadhar and W.L .at Kansar 
 
0.98 
0.94 
0.97 
0.75 
2 
W.L at Benibad &
W.L at Hayaghat 
0.91 
0.63 
0.90 
0.86 
0.90 
3 
W.L .at Kansar &
W.L at Benibad 
 
0.0047 
0.68 
0.39 
0.64 
The above table shows that there is good relationship between the water level at Dubbadhar and water level at Kansar in Nepal and the second good relationship is between the water level at Benibad and water level at Hayaghat in India. But the water level at Kansar in Nepal in not so correlated with the water level at Benibad. This may be due to the different tributaries of Bagmati between Kansar and Benibad. This shows that the trend of Bagmati River at Dubbadhar and Kansar is same and also the trend at Benibad and Hayaghat is more or less same.
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LAG TIME ANALYSIS IN BAGMATI: 
Water level curves shows that the lagging time between different sites are as follows:
S.No 
Between 

LAG Time 
1. 
Dubbadhar and Kansar 
Less than 
24 hours 
2. 
Kansar and Benibad 
Nearly 
24 hours 
3. 
Benibad and Hayaghat 
Less than 
24 hours 
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