• google scholor
  • Views: 4007

  • PDF Downloads: 450

Estimation of Design Flood for Rivers of Saurashtra Region Contributing into the Gulf of Khambhat

Priyanka Kumari 1 * and Sushil Kumar Himanshu1

1 Indian Institute of Technology Roorkee, Roorkee, India

Corresponding author Email: priyankasiwan@gmail.com

DOI: http://dx.doi.org/10.12944/CWE.11.3.23

Design flood has been estimated for rivers of Saurashtra region contributing into the Gulf of Khambhat using deterministic as well as statistical approach for planning, design and management of hydraulic structures. By comparing the results obtained by these approaches, one can easily estimate the flow rate or peak discharge to a given design return period and can establish the suitability of approach for this study area. Nine river basins with 20 dams of Saurashtra region were analyzed in this study. Though Saurashtra is one of the most water scarce regions of India yet it suffers from the flooding problem, as the numbers of rainy days are very less and the rainfall intensity is very high. Due to being a regulated basin, dam wise study was preferred. Deterministic approach was carried out using synthetic unit hydrograph (SUH) and regional flood formulae (RFF) methods for subzone-3a provided in Central Water Commission (CWC) report, 2001. Statistical approach was carried out using Rainfall frequency analysis employingGumbel’s EV1distribution. As there is no spill by these hydraulic structures and the annual flood data for the nine river sites are heavily affected by the storage dams in the upstream. Hence these data violate the basic principle of virgin flow. Hence the analysis of these data was not attempted further. The main objective of study was to carry out the rainfall frequency analysis for these river basins to get 24 hour rainfall for a return period of 25, 50 and 100 years for an individual basin instead of using the value obtained by iso-pluvial map to estimate the design flood. The overall results reveals that due to construction of number of dams in 9 river basins, design flood estimation on each dam by using deterministic approach is more feasible.Revised design floods using SUH and RFF method on the basis of estimated rainfall indicates over-estimated and under-estimated design floods. Since the percentage difference is very less between revised SUH and revised RFF method. So, for safety purpose one with higher value should be used.


Design flood; Digital Elevation Model (DEM); Geographic Information System (GIS); Soil and Water Assessment Tool (SWAT) model; Synthetic Unit Hydrograph (SUH); Regional Flood Formulae(RFF); Gumbel’s EV1; Rainfall frequency

Copy the following to cite this article:

Kumari P, Himanshu S. K. Estimation of Design Flood for Rivers of Saurashtra Region Contributing into the Gulf of Khambhat. Curr World Environ 2016;11(3). DOI:http://dx.doi.org/10.12944/CWE.11.3.23

Copy the following to cite this URL:

Kumari P, Himanshu S. K. Estimation of Design Flood for Rivers of Saurashtra Region Contributing into the Gulf of Khambhat. Curr World Environ 2016;11(3). Available from: http://www.cwejournal.org/?p=16430


Download article (pdf)
Citation Manager
Publish History


Article Publishing History

Received: 2016-08-09
Accepted: 2016-10-25

Introduction

Flood, a natural disaster is responsible for loss of life and property world over. Floods damage property and endanger the lives of humans and animals and also affect the environment and aquatic life negatively. Floods have been occurring repeatedly in India. Approximately 40 million ha area (12%) in India has been identified as flood prone.18 For mitigating the flood disasters, various structural and non-structural measures are adopted. Structural measures include protection works and flood embankments while non-structural measures include flood forecasting, flood warning and flood plain zoning. Design flood estimates are required for the design of various hydraulic structures such as weirs, barrages, dams, embankment etc. and flood protection / relief schemes.5,14 Flood forecasts are required for operation of various flood control structures, for taking emergency measures such as maintenance of flood levees, evacuating the people to safe localities etc. Whenever rainfall or river flow records are not available at or near the site of interest, it is difficult for hydrologists or engineers to derive reliable flood estimates directly. In such situation, flood formulae developed for the region are one of the alternative methods for estimation of design floods, particularly for small-to-medium catchments. The conventional flood formulae developed for different regions of India are empirical in nature and do not provide estimates for a desired return period.

A number of studies have been carried out for estimation of design floods for various structures by different Indian organizations. Among these the prominent studies are carried out jointly by the Central Water Commission (CWC), Research Designs and Standards Organization (RDSO), and India Meteorological Department (IMD) using the method based on synthetic unit hydrograph and design rainfall, considering physiographic and meteorological characteristics for estimation of design floods3 and regional flood frequency studies carried out by RDSO using the USGS and pooled curve methods12 for various hydro-meteorological subzones of India. The concept of the geomorphologic instantaneous unit hydrograph (GIUH) was introduced by Rodriguez-Iturbe and Valdes.17 The topographic and geometric properties of the watershed and its drainage channel network are reflected by geomorphology.Snyder (1938) proposed synthetic unit hydrograph approach (SUH) for ungauged basin.21 A desirable method should satisfy the requirements of universal acceptability; ease in use with a minimum of data; robustness in nature; and reliability.14 Now a days GIS and remote sensing techniques are being used extensively to monitor the disasters like droughts and floods.7

Practically in the design of all hydrologic structures the peak flow that can be expected with an assigned frequency (say 1 in 100 years) is of primary importance to adequately design the structure to accommodate its effect. The design of bridges, culvert waterways and spillways for dams and estimation of scour at a hydraulic structure are some examples wherein flood-peak values are required. To estimate the magnitude of a flood peak the following methods are available: (1) Rational method; (2) Empirical method; (3) Unit-hydrograph technique and (4) Flood-frequency studies.10 The use of a particular method depends upon (i) the desired objective, (ii) the available data and (iii) the importance of the project. Further, the rational method is applicable only to small-size (<50 km2) catchments and the unit-hydrograph method is normally restricted to moderate-size catchments with areas less than 5000 (km2).13,15

In present study, design floods for various structures in the 9 river basins namely Wadhavan-Bhogavo, Limbdi-bhogavo, Sukhbhadar, Utavali, Padalio, Khalkhalia, Ghelo, Keri and Kalubhar have been estimated. Deterministic approach based on unit hydrograph theory developed by CWC4 and statistical approaches based on frequency analysis has been used for the design flood estimation.

Study Area and Data Availability

Saurashtra basin is a region of western India, located on the Arabian Sea coast of state of Gujarat. Saurashtra is bounded on three sides by waters of sea, namely in the north by the Gulf of Kutch with some part by the little Rann, in the west and south by the Arabian Sea and in the South-East by the Gulf of Khambhat; while in the east is the Mainland of Gujarat and are shown in Figure.1,8,9,19 The area covered by Saurashtra region is 59,360 sq. km. of which 9000 sq. Km. area is under study.20 Suarashtra basin lies between latitude 20ËšN to 24ËšN and longitude 69ËšE to 73ËšE. The rivers of Saurashtra region under study are: Wadhavan-Bhogavo, Limbdi-Bhogavo, Sukhbhadar, Utavali, Khalkhalia, Padalio, Keri, Ghelo and Kalubhar. There are 20 dams situated in these river basins. Details of river basins and dam situated in these river basins are shown in Table 1 and 4. Basin maps with dam site are shown in Figure 3 to 10.

There are 13 rain gauge stations and 9 G&D stations in these river basins which are shown in Figure 2. The rainfall data are collected from IMD as well as Kalpasar Department and G&D data are collected from Kalpasar Department of Gujarat. Details of G&D stations and raingauge stations are shown in Table 2 and 3.For Synthetic Unit Hydrograph analysis, data related to catchment like river length, catchment area and equivalent slope are required and the same are computed using SWAT model and Arc-GIS. SRTM data of 90 m resolution are used for this purpose.

 Figure 1. Location map of study area a) Subzone 3(a) of India b) River map of Gujarat (Source: Gujarat State Disaster Management Authority)


Figure 1: Location map of study area a) Subzone 3
(a) of India b) River map of Gujarat (Source: Gujarat
State Disaster Management Authority)

Click here to View figure

 

 Figure 2. Location of G&D sites and rain-gauge in river basin map


Figure 2: Location of G&D sites and rain-gauge in river basin map 
Click here to View figure

 

 Figure 3. Basin map of Wadhavan-Bhogav


Figure 3: Basin map of Wadhavan-Bhogav 
Click here to View figure

 

 Figure 4. Basin map of Limbdi-Bhogavo


Figure 4: Basin map of Limbdi-Bhogavo
Click here to View figure

 

Figure 5. Basin map of Sukhbhadar 


Figure 5: Basin map of Sukhbhadar
Click here to View figure

 

 Figure 6. Basin map of Utavali


Figure 6: Basin map of Utavali 
Click here to View figure

 

 Figure 7.Basinmap of Padalio and Khalkhalia


Figure 7: Basinmap of Padalio and Khalkhalia 
Click here to View figure

 

Figure 8. Basin map of Keri 


Figure 8: Basin map of Keri 
Click here to View figure

 

 Figure 9. Basin map of Ghelo


Figure 9: Basin map of Ghelo 
Click here to View figure

 

 Figure 10. Basin map of Kalubhar


Figure 10: Basin map of Kalubhar 
Click here to View figure

 

Table 1: Details of River Basins

Sr.No.

Basin Name

Area (km2)

Length (km)

Eq. Slope (m/km)

1

Wadhavan-Bhogavo

1517

128

1.19

2

Limbdi-Bhogavo

915

118

1.4

3

Sukhbhadar

1774

145

0.997

4

Utavali

1206

98

0.751

5

Padalio

311

50

0.779

6

Khalkhalia

436

47

0.779

7

Keri

556

110

1.537

8

Ghelo

626

94

1.565

9

Kalubhar

2047

90

1.42

 

Table 2: Details of G&D stations of Saurashtra region

Sr. No.

Station

Name

Longitude

Latitude

Type

Data Availability

(Years)

River Basin

1

Limbdi

71Ëš43'8.39"

22Ëš33'28.79"

Daily

1991-2011

Limbdi

2

Ranpur

71Ëš43'29.99"

22Ëš 21' 18"

Daily

1991-2010

Sukhbhadar

3

Bhimnnath

72Ëš 5' 59.99"

22Ëš 13' 1.2"

Daily

1999-2010

Utavali

4

Barwala

71Ëš 46' 8.4"

22Ëš12'10.79"

Daily

1991-2009

Utavali

5

Keria

71Ëš 52' 33.6"

22Ëš 6' 7.2"

Daily

1991-2010

Padalio

6

Muldharoi

71Ëš55'51.59"

22Ëš3'14.39"

Daily

1997-2010

Padalio

7

Goradka

71Ëš 28' 26.4"

22Ëš 5'20.39"

Daily

1991-2010

Keri

8

Vallabhipur

71Ëš 52' 22.8"

21Ëš 53'9.59"

Daily

1991-2010

Ghelo

9

Umrala

71Ëš 47' 56.4"

21Ëš 50'56.4"

Daily

1991-2008

Kalubhar

 

Table 3: Details of Rain gauge stations of Saurashtra region

Sr.No.

Station

Name

Longitude

Latitude

Type of Data

Data Availability

(Years)

River Basin

1

WB II

71Ëš31' 58.8"

22Ëš43' 55.19"

Hourly

1906-2003

WB

2

Sayla

71Ëš27' 21.6"

22Ëš32' 42"

Hourly

1969-2003

WB

3

Chotila

71Ëš12' 46.79"

22Ëš25' 15.59"

Hourly

1968-2003

WB

4

Limbdi

71Ëš43' 19.19"

22Ëš34' 15.6"

Hourly

1991-2010

Limbdi

5

Dhandhuka

71Ëš 58'29.99"

22Ëš 23'27.59"

Hourly

1901-2006

Sukhbhadar

6

Chorvira

71Ëš 45'28.79"

22Ëš 20' 45.6"

Hourly

1991-2010

Sukhbhadar

7

Lakhavad

71Ëš 31'55.19"

22Ëš 19' 12"

Hourly

1982-2010

Sukhbhadar

8

Dholera

72Ëš11'41.99''

22Ëš15'7.19"

Hourly

1901-2006

Sukhbhadar

9

Bhavnagar

72Ëš 8' 13.2"

21Ëš 46' 55.2"

Hourly

1901-2006

Kalubhar

10

Vallavipur

71Ëš52'44.4"

21Ëš53'27.59"

Hourly

1960-2003

Ghelo

11

Umrala

71Ëš48' 21.59"

21Ëš 50' 38.4"

Hourly

1961-2007

Kalubhar

12

Dedava

71Ëš21' 18"

21Ëš53' 45.6"

Hourly

1982-2010

Kalubhar

13

Pipardi

71Ëš20' 9.59"

21Ëš50' 9.59"

Hourly

1983-2007

Kalubhar

 

Table 4: Details of Dam with river-wise

Sr. No.

Name of River

Name of the Dam

Location

Area (km2)

River Length (km)

Eq. Slope (m/km)

Longitude

Latitude

1

Wadhwan-Bhogavo

WB I

71°28’57.7”

22°40’49.6”

389

50

1.86

WB II

71°36’26.8”

22°43’17.2”

159

14

1.22

WB III

71°48’50.0”

22°39’45.6”

303

24

1.81

2

Limbdi-Bhogavo

LB I

71°27' 21.6"

22°28' 48"

329

33

1.727

LB II

71°36' 39.6"

22°32' 34.8"

201

19

2.142

LB III

71°56' 45.6"

22°33' 17.9"

192

36

1.504

3

Sukhbhadar

Sukhbhadar

71°32' 13.2"

22°20' 45.6"

591

45

1.937

Goma

71°30' 3.6"

22°14' 23.9"

165

24

3.211

4

Utavali

Khambhada

71°50' 41.9"

22°10' 22.8"

255

40

2.431

Senthali

71°44' 27.6"

22°9' 43.2"

62

18

3.332

5

Keri

Bhimdad

71°34' 37.2"

22°4' 51.6"

126

24

2.931

Gala

71°34' 22.8"

22°2' 45.6"

169

26

3.892

6

Ghelo

GheloSomnath

71°24' 7.2"

22°3' 10.8"

56

12

5.662

GheloItaria

71°23' 49.2"

21°58' 4.8"

111

16

3.681

Limbali

71°31' 48"

21°58' 8.4"

142

27

3.427

Navagam

71°47' 24"

21°56' 20.4"

60

15

1.988

7

Kalubhar

Kalubhar

71°38' 27.6"

21°51' 28.8"

592

46

3.139

Rangholi

71°39' 35.9"

21°45' 36"

397

31

2.570

Malpara

71°32' 56.4"

21°51' 39.6"

114

23

2.470

8

Padalio

Bhambhan

71°41' 6"

22°6' 0"

66

14

3.66


Methodology

In this study, deterministic approach based on unit hydrograph theory and statistical approaches based on frequency analysis are used for design flood estimation.

1 Deterministic Approach

Due to paucity of data, regional approach based on synthetic unit hydrograph developed by Central Water Commission (CWC), 1987 has been used.2 The study area falls under the subzone 3(a).
 

  • Synthetic Unit Hydrograph (SUH) method

The following relationship for SUH method has been developed by CWC (1987):

tp= 0.433(L/Sc)0.704  (1)
qp =1.161/(tp)0.635    (2)
TB = 8.3758(tp)0.512   (3)
W50 = 2.284/(qp)1.00  (4)
Qp=qp * A                   (5)
W75 =1.331/(qp)0.991  (6)
WR50 = 0.827/(qp)1.023  (7)
WR75 = 0.561/(qp)1.037    (8)
Tm =tp+ 0.5                     (9)
 

Where,

A = Total catchment area in km2
L = Length of longest main stream along the river course in km
Sc = Equivalent stream slope in m/km
tp= Time from the centre of effective rainfall duration to the peak in hr.
qp = Peak rate of discharge in cumec  per sq. km.
Qp = Peak discharge of U.G. in m3/s
TB = Base width of U.G. in hr.
Tm = time from the start of rise to the peak of U.G. in hr.
W50 = Width of U.G. measured at 50% of peak discharge ordinate in hr.
W75 = Width of U.G. measured at 75% of peak discharge ordinate in hr.
WR50 = Width of rising limb of U.G. measured at 50% of peak discharge ordinate in hr.
WR75 = Width of rising limb of U.G. measured at 75% of peak discharge ordinate in hr.

Regional flood formulae method

The regional flood formulae have been developed by CWC to estimate 25, 50 and 100 year return period flood values. The meteorological variability has been accounted from region to region in these formulae. The others factors such as shape of the catchment, slope of the stream etc, which have influence on the peak, have also been included in these formulae thereby improving over most of the limitations of the empirical / rational formula. Thus to estimate design flood for sub-zone 3(a), Regional flood formula is given as2:

formula10

Where,

a, b, c, d and e are coefficient and the value of this coefficient is provided in CWC report.
QT = Design flood for a desired return period T in m3/s
A = Catchment Area in km2
S = Equivalent slope of main stream in m/km
Rt = Storm depth of return period t in cm
L = Longest length of main stream in km

Thus,

Qâ‚‚â‚… = 1.005 * A(0.978) * S(0.25) * Rt(1.19) / L(0.618)                                                                                (11)
Qâ‚…â‚€ = 1.164* A(0.947) * S(0.242) * Rt(1.143) / L(0.566)                                                                              (12)
Q₁₀₀ = 1.161* A(0.96) * S(0.241) * Rt(1.126) / L(0.568)                                                                             (13)

Statistical Approach

The statistical approach, otherwise also called frequency analysis, may be performed on the past recorded data of annual peak data series. Frequency analysis is carried out on the available record of annual flood peak discharge or annual rainfall events of the region.

Frequency Analysis for individual gauged sites

Frequency analysis study interprets a past record of events to predict the future probabilities of occurrence and estimate the magnitude of an event corresponding to a specific return period.1 If the event records are of sufficient length and reliability, they may yield satisfactory estimates. The method, however, does not provide a hydrograph shape but gives only a peak discharge of known frequency. The processed data series are to be analysed to ensure that the fundamental assumption of frequency analysis are satisfied. The data series is to be checked for randomness, presence of trend and outliers. The presence of trend is tested by using Kendall’s rank correlation test and Turning point test. The presence of randomness and outliers is tested by Anderson’s correlogram test and Chow test respectively. Detailed at site flood frequency analysis is carried out by using various distributions like Normal, Log-Normal, Pearson type III, Log-Pearson type III, Gumbel’s Extreme value distribution.9 Gumbel EV1 is the commonly used distributions and the details about these distributions are given below.1,15,16

Gumbel EV-1 type distribution

It is one of the most commonly used distributions in flood frequency analysis and was introduced by Gumbel in 1941. It is widely used for extreme values in hydrologic and meteorological stud­ies for prediction of flood peaks, maximum rainfalls, maximum wind speed, etc. It is the double exponential distribution (known as Gumbel’s distribution or extreme value type 1 or Gumbel’s EV-1 distribution). The CDF of EV-1 distribution is defined as

F (x) = exp [-exp(-(x-u)/α                                                                                                  (14)

Where, u and a are the location and scale parameters of the distribution.
Using method of moments, u and a are obtained by following equation:

 formula15,16

Where,  and SX are mean and standard deviation of the variate X.
Equation (16) can be written in the reduced variate form as

F(y) =exp (-exp (-YT))                                                                                                          (17)

Where,

formula18

 

The reduced variateYT can be written in terms of return period, T, by replacing F(x) by 1-1/T as

formula20


Regional flood frequency analysis

Kumar (2009), developed the Regional flood frequency relationship using L-moment approach for ungauged catchments for 17 Subzones hydro-meteorologically homogeneous. Out of 17 subzones, Saurashtra region falls under Subzone 3(a) and the relationship for this subzone developed by Kumar (2009) is given as follows11:


QT = CT * Ab  (22)


Where,

QT = Flood estimate for an ungauged catchment in m3/s for T year return period
CT = a regional coefficient
A = Catchment area in km2
b = a regional coefficient, for subzone 3(a) this value is 0.383.
Value of CT for Various return period for Subzone 3(a) are shown in Table 5.

Table 5: Value of CT for Various return period for Subzone 3(a)

Coeff. (b)

CT for Subzone 3(a)

Return Period (Years)

2

10

25

50

100

0.383

23.283

68.862

94.629

114.058

133.488


Results and Discussion

In this study initially the above approach are used for 20 dams as well as for 9 river basins on the basis of 24 hour rainfall for T year return period given in the iso-pluvial map. After rainfall frequency analysis, it is revised only for dams because these basins are heavily affected by dams situated on upstream. The result obtained by the above approach by the use of 24 hour rainfall for a T year return period given in the iso-pluvial map (IMD, Pune) are shown in Table 6 and 7 as well as developed by rainfall frequency analysis for basin wise are shown in Table 8 and 9.From Table 6, it can be seen that design flood estimates for return period of 25, 50 and 100 years for dams namely Wadhavan-Bhogavo, Limbdi-Bhogavo, Sukhbhadar, Utavali, Khalkhalia, Padalio, Keri and Kalubhar are underestimating except Ghelo which is overestimating when compares with the result obtained from Table 8. The reason behind this variation in result is the use of value T year return period 24 hour rainfall. By rainfall frequency analysis it has been found that the river basins namely Wadhavan-Bhogavo, Limbdi-Bhogavo, Sukhbhadar and Kalubhar have higher value of rainfall from what recommended by IMD Pune while Ghelo river basin has lower value. T year return period 24 hour rainfall recommended by IMD Pune for these river basinsis: R25 = 20 cm, R50 = 24 cm and R100 = 28cm. Since only 5 basins namely Wadhavan-Bhogavo, Limbdi-Bhogavo, Sukhbhadar, Ghelo and Kalubhar have sufficient rainfall data availability so by using Gumbel EV1 distribution T year return period 24 hour rainfall are estimated for 5 river basins and are shown in Table 8. Thus this estimated value of 24 hour rainfall for return period of 25, 50 and 100 years is used to revise design floods for the dams present in these river basins. Revised design floods for dams in these river basins for return period of 25, 50 and 100 years are computed and tabulated in Table 9 and from Table 9 it is found that the % difference is very less between revised SUH and revised RFF method.

By using the relationship developed by Kumar (2009), the design flood estimates for return period of 25, 50 and 100 years for dams and rivers are computed below in Table 10 and 11. From Table 10 and 11 it is found that the % difference is very large between L-moment and revised SUH method. L-moment method underestimates the design floods for dams as well as river basins.

The annual flood data for the nine river sites are heavily affected by the storage dams in the upstream. Hence these data violate the basic principle of virgin flow. Hence the flood frequency analysis of these data was not attempted further.

Table 6: Design flood (Cumec) for 20 dams

Basin Name

Dam

SUH Method

RFF method

Qâ‚‚â‚…

Qâ‚…â‚€

Q₁₀₀

Qâ‚‚â‚…

Qâ‚…â‚€

Q₁₀₀

Wadavan-Bhogavo

WB I

1345.53

1676.05

1868.75

1261.18

1566.76

1882.22

WB II

754.02

929.89

1105.27

1039.06

1290.82

1550.72

WB III

1348.32

1666.65

2029.65

1544.16

1918.30

2304.54

Limbdi-Bhogavo

LB I

1303.96

1503.09

1929.6

1384.68

1720.19

2066.53

LB II

1140.6

1389.58

1658.26

1293.99

1607.52

1931.18

LB III

749.15

926.93

1103.8

734.48

912.44

1096.15

Suhkbhadar

Goma

1034.31

1204.52

1497.79

983.51

1221.82

1467.82

Sukhbhadar

1789.9

2550.71

3050.28

2046.92

2542.89

3054.88

Utavali

Senthali

437.17

533.07

630.93

455.27

565.58

679.46

Khambhada

1118.01

1380.51

1642.09

906.15

1125.71

1352.36

Padalio

Bhambhan

510.88

623.08

735.27

578.64

718.84

863.58

Keri

Bhimdad

745.08

914.13

1082.44

738.48

917.41

1102.12

Gala

1057.66

1294.23

1531.72

1005.44

1249.05

1500.54

Ghelo

Somnath

562.15

683.43

804.03

604.54

751.02

902.24

Itaria

830.22

1013.49

1197.47

887.28

1102.27

1324.21

Limbali

895.08

1094.84

1251.58

802.56

997.01

1197.75

Navagam

388.78

475.89

562.89

433.71

538.80

647.29

Kalubhar

Malpara

721.43

882.32

1044.39

699.35

868.80

1043.73

Rangholi

1871.56

2307.04

2744.37

1874.26

2328.39

2797.20

Kalubhar

1904.34

2370.23

2843.88

2149.38

2670.16

3207.78

 

Table 7: Design flood (Cumec) for 9 river basins

Sr. No.

Basin Name

SUH Method

RFF method

Qâ‚‚â‚…

Qâ‚…â‚€

Q₁₀₀

Qâ‚‚â‚…

Qâ‚…â‚€

Q₁₀₀

1

Wadhavan-Bhogavo

2710.72

3472.33

4228.19

2473.45

3129.90

3832.12

2

Limbdi-Bhogavo

1832.21

2326.2

2821.62

1638.00

2095.30

2548.53

3

Sukhbhadar

3192.12

4068.33

4947.0

2519.04

3200.88

3926.56

4

Utavali

2208.94

2686.26

3101.49

2085.64

2630.09

3213.83

5

Padalio

754.38

952.94

1149.27

1178.52

1480.72

1787.92

6

Khalkhalia

1032.13

1319.2

1572.23

815.14

1038.28

1248.04

7

Keri

1306.05

1635.35

1971.73

1237.48

1581.81

1912.50

8

Ghelo

1413.24

1791.38

2170.07

1337.6

1709.47

2069.72

9

Kalubhar

3862.14

4952.84

5334.61

4274.00

5256.78

6464.61

 

Table 8: 24 hour Rainfall (cm) for T year return period for river basins

Sr. No.

Basin Name

R25

R50

R100

After analysis

As per Iso-pluvial map

After analysis

As per Isopluvial map

After analysis

As per Isopluvial map

1

Wadhavan-Bhogavo

25

20

28

24

32

28

2

Limbdi-Bhogavo

34

20

38

24

41

28

3

Sukhbhadar

21

20

25

24

28

28

4

Ghelo

18

20

21

24

23

28

5

Kalubhar

21

20

24

24

27

28

 

 Table 9: Revised design flood for T year return period by SUH and RFF methods for dams


Table 9: Revised design flood for T year return
period by SUH and RFF methods for dams

Click here to View table

 

Table 10. Design flood for T year return period by L-moment method for dams 


Table 10: Design flood for T year return
period by L-moment method for dams

Click here to View table

 

Table 11: Design flood for T year return period for river basins

Basin Name

Area (km2)

Return Period (years)

25

PD

50

PD

100

PD

L-moment

SUH

L-moment

SUH

L-moment

SUH

WB

1517

1564.38

2710.72

36

1885.57

3472.33

40

2206.78

4228.19

42

LB

915

1288.99

1832.21

21

1553.64

2326.20

25

1818.30

2821.62

29

Sukhbhadar

1774

1661.01

3192.12

34

2002.05

4068.33

37

2343.10

4947.0

40

Utavali

1206

1432.78

2208.94

31

1726.96

2686.26

34

2021.15

3101.49

37

Padalio

311

852.61

754.38

0

1027.67

952.94

1

1202.73

1149.27

3.6

Khalkhalia

436

970.39

1032.13

17

1169.63

1319.20

21

1368.88

1572.23

23

Keri

556

1065.09

1306.05

13

1283.78

1635.35

18

1502.47

1971.73

21

Ghelo

626

1114.58

1413.24

17

1343.43

1791.38

21

1572.28

2170.07

24

Kalubhar

2047

1754.62

3862.14

59

2114.87

4952.84

59

2475.14

5334.61

60

[Note: PD- % Difference]

Conclusions

After the analysis of these river basins and dams situated on it, the following conclusions are drawn:

  • For the study area, 24 hr rainfall for the return period of 25, 50 and 100 years are different for 9 river basins which also differs from iso-pluvial map recommended by IMD, Pune for this region.
  • Revised design floods using SUH and RFF method on the basis of estimated rainfall indicates over-estimated and under-estimated design floods.
  • Due to construction of number of dams in 9 river basins, design flood estimation on each dam by using deterministic approach is more feasible.
  • The percentage difference is very less between revised SUH and revised RFF method. So, for safety purpose one with higher value will be used.
  • Regional flood frequency relationship based on L-moment under-estimates the design floods with average percentage difference of 32.023% for dams and 28.28% for river basins.
  • The reason for large average percentage difference was investigated and the data analysis reveals that there are large storages in these basins and hence application of either RFF or L-moment based methods may not be applicable.


Acknowledgement

We acknowledge the IMD, Pune as well as Kalpasar Department of Gujarat, India, for providing hydro-meteorological data of the Saurashtra region of Gujarat.

References
 

  1. Chow, V.T., Maidment, D.R. and Mays, L.W. ‘Applied Hydrology’, McGraw-Hill, New York, (2010).
  2. CWC, ‘Flood estimation report for Mahi and Sabarmati (Sub-zone-3(a))’, Directorate of Hydrology, New Delhi, (1987).
  3. CWC, ‘Flood estimation report for Upper Narmada and Tapi (Sub-zone-3(C))’ Report No. UNT/7/1983, Directorate of Hydrology, New Delhi, (1983).
  4. CWC, ‘Manual of estimation of Design Flood’, Hydrology studies Organisation, New Delhi, (2001).
  5. Himanshu, S. K., Garg, N., Rautela, S., Anuja, K. M., & Tiwari, M., ‘Remote sensing and GIS applications in determination of geomorphological parameters and design flood for a Himalayan river basin, India’, Res. J. Earth Sci, 1(3), 11-15, (2013).
  6. Himanshu, S. K., Pandey, A., & Palmate, S. S.,‘Derivation of Nash Model Parameters from Geomorphological Instantaneous Unit Hydrograph for a Himalayan River using ASTER DEM’, Proceedings of International Conference on Structural Architectural and Civil Engineering, Dubai, (2015).
  7. Himanshu, S. K., Singh, G., &Kharola, N. ‘Monitoring of Drought using Satellite Data’,International Research Journal of Earth Sciences, 3(1), 66-72, (2015)
  8. http://guj-nwrws.gujarat.gov.in/ (Narmada Water Resource and Kalpasar Department).
  9. http://www.gsdma.org/hazards/flood.aspx(Gujarat State Disaster Management Authority).
  10. http://www.mapmyindia.com/solutions/emergency-and-disaster-management(Emergency and Disaster Management).
  11. Kumar, R. ‘Regional flood frequency analysis in India, D. thesis report, Department of Hydrology, IIT Roorkee, (2009).
  12. Kumar, R., Singh, R. D., & Seth, S.M., ‘Regional flood formulae for seven subzones of zone 3 of India’, Journal of Hydrology, 4:240-244, (1999).
  13. Mutreja, K. N., Applied Hydrology, McGraw-Hill, New York, (1986).
  14. Pandey, A., Himanshu, S. K., Mishra, S. K., & Singh, V. P. ‘Physically based soil erosion and sediment yield models revisited’,CATENA, 147, 595-620, (2016).
    CrossRef
  15. D.S.O. Estimation of Design Discharge based on Regional Flood Frequency Approach for Subzone 3(a), 3(b), 3(c) and 3(e). Bridges and Floods Wing Report No. RBF-20, (1991).
  16. Rao, A. R. &Hamed, K. H. ‘Flood Frequency Analysis’, CRS Press, Washington, D.C., (2000).
  17. Rodriguez-Iturbe, I. and Valdes, J.B., ‘The geomorphologicstructure of hydrologic response, Water Res. Res., 15(6), 1409–1420, (1979).
    CrossRef
  18. Sathe, B. K., Khir, M. V. &Sankhua, R. N., ‘Rainfall analysis and design flood estimation for Upper Krishna River Basin Catchment in India’, International Journal of Science &Engg. Reasearch,3 (8), ISSN 2229-5518, (2012).
  19. Singh, V.P., Hydrologic systems: Rainfall-runoff modeling, N J Prentice Hall. Englewood, 1, (1988).
  20. Subramanya, K. ‘Engineering Hydrology’, McGraw-Hill, New York, (2009).
  21. Snyder, F. F., “Synthetic Unit graphs”, Transactions of American Geophysics Union, 19th Annual Meeting, Part 2, p. 447-454 (1938).
    CrossRef