project rehabilitation report of kabini dam,

Project Rehabilitation Report of Kabini Dam

i | P a g e

Project Rehabilitation Report

of Kabini Dam, Karnataka Water Resources Department

Doc. No.: CDSO_DSR_PRR_ KA06HH0098_KaWRD_v1.0

September 2019

Central Water Commission

Ministry of Water Resources,

River Development & Ganga Rejuvenation

Government of India


ii | P a g e

THIS PAGE IS LEFT BLANK INTENTIONALLY


iii | P a g e

Quality Control:

Version Date Writers/Contributors Checked by

1 29/09/2019 Dr. Hadush S Hagos (HSH) Pankaj Kumar Awasthi (PKA Anil Kumar Verma (AKV)

Rajiv Kumar Sawarn

Issued/Copied to:

I/C Date Name Organisation

Issued 30/09/2019 Shri. Pramod Narayan Central Water Commission


iv | P a g e

Abbreviations

DRIP Dam Rehabilitation & Improvement Project

CWC Central Water Commission

CPMU Central Project Management Unit

CSV Construction Site Visit

SPMU State Project Management Unit

IA Implementation Agency

PIC Project Identification Code

DSRP Dam Safety Review Panel

PST Project Screening Template

DFR Design Flood Review

MSL Mean Sea Level

FRL Full Reservoir Level

MWL Maximum Water Level

TBL Top Bund Level (Top Level of Dam)

MDDL Maximum Draw Down Level

LSL Lowest Sill Level

DSL Dead Storage Level

U/S Upstream

D/S Downstream

El. Elevation

L/B Left Bank

R/B Right Bank

PMF Probable Maximum Flood

SPF Standard Project Flood

CD Works Cross Drainage Works

VRB Village Road Bridge

WBM Water Bound Macadam

NDT Non Destructive Testing

DHARMA Dam Health And Rehabilitation Monitoring Application

O & M Operation and Maintenance

EAP Emergency Action Plan


v | P a g e

ESMF Environmental and Social Management Framework

E & S specialists Environmental and Social Specialists

HM Works Hydro-Mechanical Works

EM Works Electro-Mechanical Works

SCADA Supervisory Control and Data Acquisition System

DG Set Diesel Generator Set

MW Mega Watt

MU Million units

Ha Hectare

MCM Million Cubic Metre

Deg. Degree

Min. Minute

Sec. Second

CM Construction management

QC Quality control

m meter

m3 Cubic meter

m3/sec Cubic meter per second

Km2 Square kilometre

Mcm Million cubic meter

TNWRD Tamil Nadu Water Resource Department

TANGEDCO Tamil Nadu Generation and Distribution Corporation

KWRD Kerala Water Resource Department

KSEB Kerala State Electricity Board

MPWRD Madhya Pradesh Water Resource Department

UJVNL Uttarakhand Jal Vidyut Nigam Limited

DVC Damodar Valley Corporation


vi | P a g e

DRIP Component Wise Project Cost

KaWRD Initial/Revised Projects & Cost

BACKGROUND

In April 2012, the Central Water Commission

(CWC) with assistance from the World Bank,

embarked upon a six year Dam

Rehabilitation and Improvement Project

(DRIP) at a preliminarily estimated initial cost

of Rs.2100 Crore targeting rehabilitation and

improvement of about 250 dams initially of

six, later of nine implementing agencies -

namely: MPWRD, OWRD, TNWRD,

TANGEDCO, KWRD, KSEB, KaWRD,

UJVNL and DVC.

In June 2018, the project was extended by

two years, until June 2020. The current

revised cost for DRIP is Rs.3466 Crore out of which Rs. 2920.5 Crore is allocated for

Component 1 (Rehabilitation and Improvement of Dams and Associated Appurtenances),

Rs.232.5 Crore for Component 2 (Dam Safety Institutional Strengthening), and Rs.313 Crore

for Component 3 (Project Management). Appropriate assistance is also provided under

DRIP to develop O & M Manuals and Emergency Action Plans (EAP) for these dams. The

project also promotes new technologies and improves institutional capacities for dam safety

evaluation and implementation at the Central and State levels as well as in some identified

premier academic and research institutes in the country. The actual total number of dams

under DRIP stands at 223.

The Implementing Agencies for DRIP are the Water Resources Departments and State

Electricity Boards in the participating States and Damodar Valley Corporation (DVC) with

Central Water Commission at Central Level. State Implementing Agencies are responsible

for implementation of works of dams under their charge. Co-ordination and management of

such works within a State rests with the

concerned State Project Management

Unit (SPMU). Overall project oversight

and coordination is carried out by Central

Project Management Unit (CPMU) headed

by the Project Director with assistance of

an Engineering and Management

Consultant.

Karnataka Water Resource Department

(KaWRD) joined DRIP in August 2014

with initial number of dams totalling 31.

Later, KaWRD dropped 9 dams and

continuing in DRIP with 22 dams.

Preliminarily estimated initial DRIP project

cost for KaWRD was Rs.276.1 Crore and

the revised actual current project cost is

Rs.581.2 Crore.



vii | P a g e



viii | P a g e

Table of Contents

Abbreviations .......................................................................................................... iv

1. EXECUTIVE SUMMARY .................................................................................. 1

2. PROJECT DETAILS ......................................................................................... 2

2.1 Project Description .......................................................................................................... 2

2.2 Project Location ............................................................................................................... 2

2.3 Project Benefits ................................................................................................................ 2

2.4 Dam and Reservoir Features (Before rehabilitation under DRIP) ............................... 3

2.5 Any Emergency Spillway, Fuse Plug etc. ...................................................................... 4

2.6 Details of previous dam incidents, if any ...................................................................... 4

2.7 PST Details ....................................................................................................................... 5

2.8 DSRP, CPMU and World Bank Recommendations and Compliance ......................... 5

2.9 Scope of Rehabilitation Works as per PST ................................................................... 5

2.10 Drawings ......................................................................................................................... 12

3. DAM VISITS (PST STAGE) ............................................................................ 19

3.1 Dam Inspections ............................................................................................................ 19

3.2 Summary of observations made by CPMU ................................................................. 19

4. DESIGN FLOOD REVIEW (DFR) ................................................................... 19

4.1 DFR Outcome ................................................................................................................. 19

4.2 Brief Summary of Review .............................................................................................. 19

4.3 Recommendations ......................................................................................................... 19

5. REHABILITATION WORKS CARRIED OUT ................................................. 19

5.1 Summary of Investigations ........................................................................................... 19

5.2 Main Dam Works ............................................................................................................ 20

5.3 Basic facilities ................................................................................................................ 20

6. INSTRUMENTATION ..................................................................................... 21

6.1 List of existing instruments installed in dam and their condition ............................ 21

6.2 Details of new instruments installed ........................................................................... 21

6.3 CPMU Recommendations ............................................................................................. 21

7. PROCUREMENT OF WORKS ....................................................................... 22

7.1 Package wise details ..................................................................................................... 22

7.2 Details of Bidding process ............................................................................................ 23

7.3 Reason for Variation, if any .......................................................................................... 23

7.4 Litigation / Arbitration, If Any ....................................................................................... 23

8. THIRD PARTY CONSTRUCTION SUPERVISION VISITS BY CPMU ........... 23


ix | P a g e

8.1 Summary of Visits undertaken ..................................................................................... 23

8.2 Summary of Third-Party Material Testing ................................................................... 23

8.3 Summary of Major Recommendations ........................................................................ 23

8.4 Summary of Compliance by SPMU .............................................................................. 26

8.5 Summary Special Visits made by CWC/World Bank/Expert Committee .................. 26

8.6 Summary of Technical Assistance provided by CPMU ............................................. 26

9. ENVIRONMENTAL AND SOCIAL MANAGEMENT FRAMEWORK (ESMF) 27

9.1 Basic Details ................................................................................................................... 27

9.2 Summary of Observations ............................................................................................ 27

9.3 Details of ESMF/EIA study (if any) ............................................................................... 27

10. OTHER NON-STRUCTURAL INTERVENTIONS ........................................... 31

10.1 Basic Details ................................................................................................................... 31

10.2 Summary of Observations ............................................................................................ 31

11. PENDING REHABILITATION WORKS .......................................................... 31

11.1 Details of pending works .............................................................................................. 31

11.2 Further course of action ................................................................................................ 31

12. REFERENCES ............................................................................................... 31

LIST OF FIGURES

Figure 2-1: Index Map of Kabini Dam ................................................................................................ 21

Figure 2-2: Google Map of Kabini Dam ............................................................................................. 22

Figure 2-3: Water Catchment Map of Kabini Dam............................................................................ 23

Figure 2-4: Layout Map of Kabini Dam…………………………………………………………............24

Figure 2-5: Logitudinal Section of Kabini Dam ................................................................................ 25

Figure 2-6: Typical Cross Section of Kabini Earth Dam ................................................................. 26

Figure 2-7: Cross section of Kabini Masonary Dam ........................................................................ 27

LIST OF ANNEXURES

Annex A: PST Approval Letter .............................................................................. 33

Annex B: Drawings issued for Rehabilitation measures .................................... 37

Annex C: Completion Certificate .......................................................................... 45

Annex D: ESMF OK Card ....................................................................................... 51

Annex E: Third-party Test Results ........................................................................ 55

Annex E: Photographs Before and After Rehabilitation Works ......................... 59

Annex F: DBA and Inundation Maps .................................................................... 77


1 | P a g e

1. EXECUTIVE SUMMARY

This Project Rehabilitation Report (PRR) is for Kabini Dam, which is one of the 22

dams under DRIP in the state of Karnataka. The Dam Safety Review Panel (DSRP)

inspected the dam on 22nd May 2015 and recommended both structural & non-

structural measures to be taken up by the dam authorities.

DSRP main recommendations included reaming of porous and foundation drains;

repair of spillway stilling basin; repair of right bank canal intake structures; raking and

pointing of upstream face of non-overflow masonry dam section; repair of worn-out

roller track of gate grooves and replacement of rubber seals as necessary; removal

of vegetative growth in the toe drain; provision of man holes along toe of the dam;

provision of additional V-notch weir; and provision of Casagrande type vertical stand

pipe piezometers. Non-structural measures included review of design flood, reservoir

siltation surveys; dam stability analysis; preparation of EAP and O&M manual.

As per the PST, the original peak design flood for Kabini Dam was 5,497.71 cumec

with a corresponding MWL of 696.16 m and the revised design flood (PMF) under

DRIP worked out to be 15,762.56 cumec. Flood routing study carried out by the

SPMU as part of the Dam Break Analysis (DBA) reveals that the revised MWL is at

EL 698.4 m, which is 2.24 m above the original MWL/FRL of 696.16 m. The TBL is at

EL 700.7 m and the available freeboard above the revised MWL is 2.3 m, which is

more than the minimum recommended 1.50 m as per IS 10635.

Following DSRP recommendations, rehabilitation works carried out under DRIP

included:

Civil Works:

• Improvements of drainage gallery and reaming of porous & drainage holes.

• Restoration of baffle blocks in the stilling basin.

• Providing shotcreting to concrete surface and repointing to masonry surface of right bank canal sluice.

• Providing shotcreting to concrete surface of spillway pier & improvements to masonry surface of non-overflow sections.

• Restoration of downstream earthen embankment slope.

• Providing barbed wire fencing around downstream periphery.

• Construction of security booths.

• Improvements to service road of drainage gallery.

• Providing and fixing CCTV surveillance.

• Improvements to electrical system.

• Providing fire extinguisher system.

HM Works: Replacement of damaged portion of catwalk.

The rehabilitation works were executed under 2 contracts (Civil & HM) at a total

completion cost of Rs. 1006.88 Lakhs, which included one variation order of 165.3

Lakhs for additional works in the repair of stilling basin baffle blocks.

Dam Break Analysis (DBA) and inundation maps prepared by SPMU were reviewed

and approved by CPMU. Draft Emergency Action Plan (EAP) and Operation and

Maintenance (O&M) manual prepared by the SPMU are under review process by

CPMU.


2 | P a g e

2. PROJECT DETAILS

The Kabini dam is located across Kabini River in Kodagu district, Karnataka state at

Latitude of 75º54’20” N and Longitude of 12º29’30” E. It was completed in the year

1974. The project consists of an earthen dam 2478 m long and 7.32 m dam crest

width. It has 80.77 m long spillway with 4 nos. of radial gates having discharge

capacity of 5,497.71 cumec.

The TBL, FRL, original MWL and Spillway Crest level are at EL 700.7 m, 696.16 m,

696.16 m and 684 m, respectively. The gross storage at FRL is 552.7 MCM (or 19.52

TMC).

2.1 Project Description

Sl. No.

Item Details

a. Project Identification Code (PIC) KA06HH0098

b. Project Name Kabini Dam

c. River Basin Cauvery

d. Sub River Basin Kabini

e. River/Stream Kabini

f. Catchment area (km2) 2141.90

g. Year of commencement of project 1959

h. Year of completion of project 1974

2.2 Project Location

Sl. No.

Item Details

a. State Karnataka

b. District Mysore

c. Earthquake Zone II

d. Survey of India Map Ref No’s 57 D & 58 A

e. Nearest City Heggadadevana Kote

f. Nearest Airport Mysore

g. Nearest Railhead Mysore

h. Name of Immediate U/S Project Banasursagar Dam (Kerala)

i. Name of Immediate D/S Project Hullahalli Anicut

j. Latitude in Deg., Min, Sec. (North) 11º56’27”

k. Longitude in Deg., Min, Sec. (East) 76º20’17”

2.3 Project Benefits

Sl. No. Item Details

a. Type of Project Multipurpose


3 | P a g e

Sl. No. Item Details

b. Gross Command Area (Ha) 45748

c. Culturable Command Area (Ha) 44534

d. Annual Irrigation Potential (Ha) 45748

e. Hydropower –

Installed Capacity (MW) 20

f. Hydropower –

Firm Power (MW) 20

g. Hydropower –

Average Annual Generation (MU) 30

h. Domestic/Municipal/Industrial Water –

Annual Quantum (MCM) 79.28

i. Domestic/Municipal/Industrial Water –

Area and Population Benefitted Mysore Tq & H.D. Kote tq

j. Flood Protection –

Flood Protected Area (Ha) Nil

k. Flood Protection –

Details of Area Benefitted Nil

l. Details of Tourism/Recreational Facilities Nil

2.4 Dam and Reservoir Features (Before rehabilitation under DRIP)

Sl. No.

Item Details

a. Full Reservoir Level (m) 696.16

b. Original Maximum Water Level (m) 696.16

c. Gross Reservoir Storage Capacity at FRL (Mm3 )

552.7

d. Live Storage Capacity (Mm3 ) 453.07 (as per O&M manual)

e. Revised Live Storage Capacity, if any

(Mm3 ) 453.07

f. Date of bathymetric survey, if any 2007 – 2008

g. Dam Type Composite (Earth Cum Masonry Dam)

h.

Length of Dam at Top (m)

i) Total length of the main dam

ii) Length of embankment dam

iii) Length of masonry/concrete dam

2732.55 (as per O&M manual)

2478.02

254.53

i. Number and length of dykes (No. & m) Nil

j. Top of dam (El. in m.) 700.7

k. Top Level of Upstream Parapet Wall of main dam (El. in m.)

-

l. Height of Dam (m)

i) Embankment dam – above river


4 | P a g e

Sl. No.

Item Details

bed level (up to dam top without camber)

ii) Concrete/Masonry dam – above deepest foundation level (up to dam top)

28.95

57.60

m Top width of main dam (m) 7.32

n. Spillway details

i) Location Middle

ii) Type of spillway Ogee

iii) Length of spillway (m) 80.77

iv) Spillway crest level (m) 684

v) Type of Gate Radial

vi) Number and size of gates (no. and

m. x m.) 4, 12.19 X 12.19

vii) Number and thickness of piers (no.

and m. x m.) 3, 7.62 (as per O&M manual)

o.

Outlet/Sluice details

i) In Embankment dam

• Number

• Size (Width (m). x Height (m).)

• Location

• Invert level El. (m)

• Discharging capacity (m3/s)

ii) In Concrete/Masonry dam

• Number

• Size (m. x m.)

• Location

• Invert level El. (m)

• Discharging capacity (m3/s)

2 Nos. LBC & 5 Nos. RBC

1.22 X 1.3, 2.44 X 3.05

LBC, RBC

685.5, 685.5

2.55, 65.13

3 Nos.

2.4 X 4.27

Middle

676.35

333.2 (as per O&M manual)

Note: All elevations are above MSL

2.5 Any Emergency Spillway, Fuse Plug etc.

Nil

2.6 Details of previous dam incidents, if any

Nil


5 | P a g e

2.7 PST Details

Sl.

No. Item Date/Cost Remarks

a. PST first received from SPMU 03/07/15

b. Proposed PST Cost (INR in Lakhs) 1470.0

c. First review by CPMU 25/08/15

d. Final review by CPMU 30/10/15

e. World Bank Approval 09/11/15 E- mail dated 09/11/2015

f. Approved PST Cost (INR in Lakhs) 1234.0

2.8 DSRP, CPMU and World Bank Recommendations and Compliance

2.8.1 DSRP Recommendations and Compliance

Compliance to DSRP recommendations as submitted by SPMU/dam authorities is

shown on pages 6 to 18 below.

2.8.2 CPMU/World Bank Recommendations and Compliance

Revised design flood (15190 cumecs) evaluated by CWC Hydrology Directorate being about 2.86 times the original design flood (5497.71 cumecs), WRD, Government of Karnataka should get the flood routing studies conducted on priority to check the adequacy of free board available and furnish these studies to Project Director (DRIP), CWC and CPMU, CWC to enable them to advice on the structural / non‐structural measures required to be taken. The requisite structural measures, as advised by Director (DRIP), should be taken up by the Government of Karnataka for implementation in a separate package.

Flood routing study was carried out by the SPMU as part of the Dam Break Analysis (DBA) and results reveal that the revised MWL is at EL 698.4 m, which is 2.24 m above the original MWL/FRL of 696.16 m. The TBL is at EL 700.7 m and the available freeboard above the revised MWL is 2.3 m, which is sufficient as per IS 10635.

Non-shrink and UV resistant cementitious materials utilising crystalline technology or Poly Ironite Ceramic Cement, or equivalent, and conforming to Indian and or European standards are recommended to be used for all surfaces exposed to high-velocity flows.

Following the recommendation from CPMU, PICC was used to repair the damaged baffle blocks in the stilling basin.

2.9 Scope of Rehabilitation Works as per PST

(a) Remedial Measures (Structural)

i. Improvements of drainage gallery and reaming of porous holes and drainage holes in drainage gallery.

ii. Restoration of baffle pier in the stilling basin.


6 | P a g e

iii. Providing shotcreting to concrete surface and repointing to masonry surface of Kabini right bank canal sluice

iv. Providing shotcreting to upstream face of spillway pier & improvements to masonry surface of Non-flow section.

v. Rehabilitation of detorated surface of spillway portion.

vi. Restoration of downstream embankment of earthen embankment slope.

vii. Providing barbed wire fencing around downstream periphery of Kabini dam.

viii. Construction of Security booths at Kabini dam.

ix. Providing and constructing manhole chambers in vulnerable reaches along toe drain.

x. Replacement damaged portion of catwalk.

xi. Providing spillway stoplog gate.

(b) Non-structural Measures

xii. Stability analysis of Kabini Dam

xiii. Setting up of warning system.

xiv. Improvements to electrical system of Kabini dam.

(c) Basic Facilities Enhancement

xv. Stability analysis of Kabini Dam

xvi. Setting up of warning system.

xvii. Improvements to electrical system of Kabini dam.


7 | P a g e


8 | P a g e


9 | P a g e


10 | P a g e


11 | P a g e


12 | P a g e

2.10 Drawings

Figure 2-1: Index Map of Kabini Dam.


13 | P a g e

Figure 2-2: Google Map of Kabini Dam.


14 | P a g e

Figure 2-3: Water Catchment Map of Kabini Dam.


15 | P a g e

Figure 2-4: Layout Map of Kabini Dam.


16 | P a g e

Figure 2-5: Longitudinal Section of Kabini Dam.


17 | P a g e

Figure 2-6: Typical Cross Section of Kabini Earth Dam.


18 | P a g e

Figure 2-7: Cross-section of Kabini Masonry Dam.


19 | P a g e

3. DAM VISITS (PST STAGE)

3.1 Dam Inspections

Sl. No.

Item Date of visit Remarks

a. Dam Safety Review Panel (DSRP) 22 May 2015

b. Site Visit made by CPMU experts -

3.2 Summary of observations made by CPMU

Nil.

4. DESIGN FLOOD REVIEW (DFR)

4.1 DFR Outcome

Sl. No.

Item Original

Value

Revised

Value Remarks

a. Inflow Design Flood (m3/s) 5497.71 15762.56 PMF

b. Spillway Capacity / Routed Outflow (m3/s)

- 7455.2 Flood routing

study by SPMU

c. Maximum Water Level (m) 696.16 698.4 TBL = 700.7

4.2 Brief Summary of Review

As per the PST, the original peak design flood for Kabini Dam was 5,497.71 cumec with a corresponding MWL of 696.16 m and the revised design flood (PMF) under DRIP worked out to be 15,762.56 cumec. Flood routing study carried out by the SPMU as part of the Dam Break Analysis (DBA) reveals that the revised MWL is at EL 698.4 m, which is 2.24 m above the original MWL/FRL of 696.16 m. The TBL is at EL 700.7 m and the available freeboard above the revised MWL is 2.3 m, which is more than the minimum recommended 1.50 m as per IS 10635.

4.3 Recommendations

• Structural measures - Nil.

• Non-structural measures – flood warning siren, EAP (to reduce risks downstream

during large controlled release and in the event of failure).

5. REHABILITATION WORKS CARRIED OUT

5.1 Summary of Investigations

Sl. No.

Item Details Remarks

a. Reservoir Bathymetric Study Carried Out in Year 2010 See SPMU DSRP Compliance report

b. Slope Stability Analysis SPMU reported it is ongoing

in KERS Ongoing


20 | P a g e

5.2 Main Dam Works

S/N Item Details Remarks

a. Works to improve stability of dam / spillway

Providing shotcreting to concrete surface of spillway

pier & improvements to masonry surface of non-

overflow section

Completed.

b. Works from hydrological angle Design flood review Completed.

c. Re-sectioning of the embankment dam because of rain-cuts / other reasons

Restoration of downstream earthen embankment slope

Completed.

d. Repairs in outlet works

Providing shotcreting to concrete surface and repointing

to masonry surface of Kabini right bank canal sluice.

Completed.

e.

Works because of Seepage / leakage issues in Gravity dams / spillways (u/s face treatment, grouting of dam body etc.)

Providing shotcreting to concrete surface of spillway

pier & improvements to masonry surface of non-

overflow section

Completed.

f. Re-drilling / Reaming of drainage holes in the dam body and in the foundations

Improvements of drainage gallery and reaming of porous

holes & drainage holes in drainage gallery.

Completed.

g. Works to rectify damages in spillway, Energy Dissipation arrangements etc.

Restoration of baffle piers in the stilling basin.

Completed.

h. Hydro-mechanical works

i. Main spillway gates & hoists Replacement of damaged

portion of catwalk Completed.

ii. Outlet gates & hoists - -

iii. Other H.M works, if any - -

iv. Standby D.G set / Backup power

- -

5.3 Basic facilities

S/N Item Details

a. Lighting Improvements to electrical

system Completed.

b. Roads Improvements to service road

of drainage gallery Completed.

c. Fencing / security provisions Providing barbed wire fencing around downstream periphery

of Kabini dam Completed.

d. Construction of new buildings / repairs to existing buildings

Construction of security booth Completed.


21 | P a g e

e. Siren / Emergency Warning System

Installed at dam site Already in use

f. Miscellaneous Providing fire extinguisher

system Completed.

6. INSTRUMENTATION

6.1 List of existing instruments installed in dam and their condition

V-notch weir, Manual reservoir water level recorder.

6.2 Details of new instruments installed

Tendering process for the following instruments is currently ongoing.

S. No. Instrument Quantity

1 Automatic Weather Station 1

2 Tiltmeters 3

3 Data centre at dam site logger, etc 1

4 Piezometers 18

5 Total station 1

6 Gate Sensor 4

7 Seismograph (As per NGRI, Hyderabad) 1

8 Accelerograph (As per NGRI, Hyderabad) 2

6.3 CPMU Recommendations

See Section 6.2 above.


22 | P a g e

7. PROCUREMENT OF WORKS

7.1 Package wise details

Work Package No.

Name of Works

Estimated

Cost

(INR in Lakhs)

Procurement

Method

Invitation for bids / NIT Issue

date

Pre-Bid Meeting

date

Bid Opening

date

Contract Agreement

No.

Contract Agreement

date

Contractor’s Name &

Address

Scheduled Duration (Months)

Scheduled Completio

n date

Contract /

Award Value (INR in Lakhs)

Completion Cost (INR in Lakhs)

Actual Date of

Completion

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1

Rehabilitation and Improvement works

to Kabini Dam under World Bank

aided DRIP program

734.7 NCB 03/10/15 19/02/16 18/03/16 86/2016-17 15/11/16

SRI NARAYANAREDDY

CLASS-1 CONTRACTOR,

CHANARAYAPATANA,TQ HASAN

DISTRICT.

24 10/11/18 815.00 980.30 25/09/18

2*

Replacement of damaged portion of cat walk of kabini

dam,PAPER BILLS, TRANSPORTATIO

N FACILITY etc

15.5 NCB 03/10/15 - -

124/2017-18

24/02/18

M/s Nandi Steel Products: Pro Sri SN Basavaraju, Class I

Contractor, No 1926/A 3rd Main,

3rd Cross, Tarala Balu Badavane,

Davanagere

2 23/04/18 15.4 12.58 30-03-18

Total 843.4 1006.88

* Final Completion Certificate for Package 2 is awaited from dam authorities.


23 | P a g e

7.2 Details of Bidding process

As per details in the above table.

7.3 Reason for Variation, if any

One variation order of amount 165.3 Lakhs was registered in the Civil works package

for change in material for repair of stilling basin baffle blocks.

7.4 Litigation / Arbitration, If Any

No litigation.

8. THIRD PARTY CONSTRUCTION SUPERVISION VISITS BY

CPMU

8.1 Summary of Visits undertaken

Sl. No. Date of visit Transmittal details of CSV Report

a. 02-03-2017 4554/11-05-20

b. 06-06-2017 4688/12-06-2017

c. 07-09-2017 5211/10-11-2017

d. 06-02-2018 5620/07-03-2018

8.2 Summary of Third-Party Material Testing

Laboratory proctor test as well as field compaction test have been carried out by

CPMU for downstream slope embankment works. The field compaction test results

were unsatisfactory and were recommended for rectification at the time. Third-party

tests results are attached in Appendix D.

8.3 Summary of Major Recommendations

1st Construction Site Visit Report

The Overall status of the works is listed below:

▪ The EIC is recommended to improve overall management of the works being

carried out using an OK card for tracking all embankment works. Other OK

cards are being used effectively and progress is well-documented. The

Contractor is working closely with the EIC to ensure the remaining works are

implemented using best engineering practices.

▪ Emergency time constraints for supply of water to Bangalore during this

drought period impacted the work being carried out in the stilling basin baffle

repair and the review of additional work is pending dewatering to assess the

performance of the shotcrete over the M60 grade steel-fibre concrete.

Recommendations:

▪ Reaming of porous drains has been completed. The porous drains have open

grates on the crest of the dam that is allowing both air and water to penetrate

the dam body and creating an environment for formation of calcareous

materials that will eventually clog the drains; CPMU recommends that a


24 | P a g e

provision be included in the current scope for closing the porous drains on the

crest with removable caps and installing “water traps” in the gallery as per IS

codes. Specifications are provided in the code for accomplishing this task.

▪ The stilling basin has been de-watered for repair of the energy dissipaters, or

“baffle” blocks. The baffle block cavities were filled with M60 grade steel-fibre

concrete and then overlaid with M20 grade wet-placed shotcrete. The

consensus during the visit was that this was a mistake. Dimple Chemical

offered to apply a thin layer of PICC cementitious mortar over the baffles.

CPMU recommends that the procedures be reviewed by SPMU, and if

necessary, corrected; the baffles will require additional monitoring for

understanding the effectiveness of the works; all documents for the approval

and tracking progress of this work need to be kept for the record. Any

additional new work that may be found necessary for safety and

completeness of the works is recommended to follow best engineering

practices and address WB requirements for deviations from the approved

scope of work.

▪ The embankment works include re-sectioning of the downstream slope in

certain areas that have consolidated back to design lines and grades. This

requires placement of soil up to 30-cm-thick in certain areas. CPMU

recognizes the difficulty in conducting this work and recommends small

benches be cut into the existing embankment, placing of suitable material and

compacting the material to 95% dry density using acceptable best

engineering practices.

2nd Construction Site Visit Report

Observations and Recommendations:

▪ Black ants have invaded the embankment on the downstream slope. These

ant colonies have perforated the embankment at numerous locations and

forming tunnels. CPMU recommends application of an environmental-friendly

pesticide while embankment works are being carried out.

▪ The reservoir level is expected to continue to drawdown and in the process

additional voids in the masonry are observed below the existing upstream

face guniting. CPMU recommends this be investigated and a scope

developed to rake and re-point the masonry sections below the waterline.

Work to be carried out as budget and time allow.

▪ A low berm has been constructed to support the re-sectioning work being

carried out. An excavator-powered vibratory roller is being used to protect the

bank while work is being carried out. CPMU also recommends silt fences be

installed along the hinge points of the berm to minimize soil erosion during the

upcoming monsoon, which has already started within the region and

recommends work be carried out fully after the wet season.

▪ Electrical work is being carried out: the electrical cables have been buried in

the embankment without conduit or wiring protection. CPMU recommends all

wiring be chased through GI or HDPE conduit and placed at least 500-mm

under the embankment slope to protect the cable. At the rock toe, the conduit

is recommended to be placed under the rock toe for protection. The final

placement is to be surveyed and marked on as-built drawings for future

reference, if required, for routine maintenance, repair or replacement.

3rd Construction Site Visit Report Observations:


25 | P a g e

Observations and recommendations

▪ Ant infestations are predominant within the embankment and project staff are

recommended to treat the embankment with environmental-friendly

pesticides. Left unattended, the ants will continue to loosen the embankment

resulting in formation of erosion rills.

▪ The downstream kerb wall masonry foundation is recommended to be

reconstructed; over the years, settlement of the embankment has resulted in

loss of foundation support and many sections of the wall are in disrepair. The

upstream wall is recommended to be studied and determination for repair of

the foundations be taken up.

Sl. No

Observation / Deficiency Remarks

1

Additional voids in masonry joints below EL 2244 ft., that is, below guniting of piers. Action to be taken for pointing (CSV-2)

Could not execute as the water level in the reservoir has raised.

2 Provision is made in the contract for chipping 100 mm thick spillway glacis concrete and redo with M-60 concrete.

It may be difficult to maintain the smooth profile of M-60 concrete to be done for 100 mm thick after chipping of the glacis for 100 mm. also by resorting to chipping using pneumatic equipment will disturb the glacis surface and the bondage between old and new concrete is also at doubt for such a shallow depth of concrete. Instead CPMU recommends for resorting to application of abrasion resistant rim coat as has been done in Almatti & Narayanpur Dam, In lieu of M-60 concrete.

3

Electrical cable for dam top illumination are run in embankment & on concrete surface by the side of kerb & Parapet without any protection. (Fig-3 & 4)

CPMU recommends for running the cables through PVC pipes embedded in earth to avoid any damages to cable and subsequent arising of any eventualities.

4

Wetness at D/s face of masonry dam (NOF) at Right flank at Ch. 1985 ft. for a width of about 3.00 m is observed below EL 2265.00 ft. (Fig-12)

Pointing to U/s face of NOF sections has been done from EL.2244 ft.(Crest level) the wetness is observed in the zone where U/s & D/s pointing is done. As no grouting is done from U/s or to the body of the dam, the seepage path might not be blocked fully.

5 Considerable quantum of seepage is observed in porous blocks nos 22, 21, 20 & 19.

Mostly these porous blocks are in the NOF section encased by the Wrap Around. Because of constraint in doing pointing to masonry joints below surface of wrap around the seepage may be considerable in these porous blocks. Project authorities must confirm whether these porous blocks are coming in the wrap around area. If so then the remedial measure is to take up the body grouting from top of dam to reduce the seepage in these porous blocks.

6 Water is coming out of drainage holes 5, 6 & 13 with pressure in 1’ pipe.

Quantum of seepage and uplift pressure is to be measured for various reservoir levels for study and decision by the designers.

7

Joints of Masonry of left training wall have opened at back side. Lot of vegetation has grown in the joints (Fig-18)

The vegetation growing in the masonry joints will further weaken the structure. Hence it is recommended for uprooting of vegetation and pointing the joints with cement mortar

4th Construction Site Visit Report Observations:


26 | P a g e

Observations and recommendations:

▪ The gallery walls remain wet in many sections even at lower reservoir water

level of 2272.45 ft during this inspection (FRL is at 2284 ft). The completed

upstream face treatment above EL 2244 ft (spillway crest level) does not

seem to have brought a noticeable effect in reducing seepages in the gallery.

As budget and time allow, CPMU recommends a geophysical scan be carried

out to assist in determining water leakage areas and develop a rehabilitation

plan to minimize and maintain the seepage within allowable limits.

▪ Other previously recommended actions include a post-rehabilitation

inspection (using ROV) of the badly eroded baffle blocks to determine the

efficacy of the works accomplished; the baffles were gunited with M15

concrete over the M60 grade cavity filling material.

▪ CPMU notes that turfing is required to protect d/s slope of the embankment

section from damages by erosion. The same to be considered for taking up

as budget and schedule allow including using Contract savings, if any. Chute

and longitudinal drains shall also be considered on the d/s embankment

slope.

▪ Between CH 1660 m and 1760 m, the d/s section of the embankment dam

crest and kerb wall have settled over 15 cm. The specific reason for this

settlement is yet to be determined and necessary rectification carried out.

No. Deficiency / Observation Remarks

1 No turfing on d/s slope of embankment dam section.

SPMU to consider using some savings from other activities to take up turfing works on d/s slope of dam. Vertical and longitudinal drains shall also be provided on d/s slope.

2 Gallery remains wet even after completion of u/s face treatment

SPMU recommended to consider geophysical scanning of the dam and determine critical leakage areas.

3 Electrical cable for dam top without protection.

CPMU recommends for running the cables through PVC pipes embedded in earth to avoid any damages to cable and subsequent arising of any eventualities.

8.4 Summary of Compliance by SPMU

Compliance letter received from SPMU against the CPMU experts’ comments during

construction site visits is shown below on page 28 to 30.

8.5 Summary Special Visits made by CWC/World Bank/Expert Committee

Nil

8.6 Summary of Technical Assistance provided by CPMU

• Review of PST. • Review of design flood.

• Provided technical guidance on maintaining quality of works as per design, contract agreement technical specification and best engineering practices.

• Third party quality control tests.

• Review of dam break analysis and inundation maps.

• Review of O&M manual (currently on-going).

• Review of EAP (currently on-going).


27 | P a g e

9. ENVIRONMENTAL AND SOCIAL MANAGEMENT

FRAMEWORK (ESMF)

9.1 Basic Details

No. Item Yes / No Remarks

a. ESMF Issue Identified in PST Yes

b. Mitigation Measures Proposed Yes

c. Any Rehabilitation and Resettlement involved No

d. Site Visit Date of CPMU E&S Specialists -

e. Site Visit Report of CPMU E&S Specialists -

9.2 Summary of Observations

ESMF management during implementation was generally satisfactory but PPE was

partially used during construction, which was later improved. ESMF OK Card is given

in Appendix E.

9.3 Details of ESMF/EIA study (if any)

Nil.


28 | P a g e


29 | P a g e


30 | P a g e


31 | P a g e

10. OTHER NON-STRUCTURAL INTERVENTIONS

10.1 Basic Details

Sl. No.

Item Yes / No Remarks

a

Emergency Action Plan (EAP)

(i) EAP Available at Site

(ii) EAP Prepared under DRIP

(iii) EAP Published

(iv) Stake holder consultations

No

Yes

No

No

Inundation maps prepared by SPMU was reviewed and approved by CPMU. EAP prepared by SPMU was reviewed by CPMU.

b. O&M Manual availability Yes O&M manual prepared by SPMU has been reviewed by CPMU.

c. Inflow Forecasting No

d. DHARMA Implementation Yes In progress. Most data uploaded.

e. Siren No Yes

10.2 Summary of Observations

Nil

11. PENDING REHABILITATION WORKS

11.1 Details of pending works

i. Finalization & Publication of EAP.

ii. Finalization & Publication of O&M manual.

iii. Completion of data entry in DHARMA.

iv. Address noted incompliances to DSRP recommendations.

11.2 Further course of action

All pending actions stated above should be completed before December 2019.

12. REFERENCES

i. PST

ii. DSRP report

iii. Construction site visit report.

iv. Information received from SPMU from time to time

v. Completion Certificate.

vi. World Bank approval

vii. Third-party test result

viii. Compliance letters from SPMU.

ix. Inundation report and maps.


32 | P a g e



33 | P a g e

Annex A: PST Approval Letter


34 | P a g e



35 | P a g e


36 | P a g e


37 | P a g e

Annex B: Drawings issued for

Rehabilitation measures


38 | P a g e



39 | P a g e


40 | P a g e


41 | P a g e


42 | P a g e


43 | P a g e


44 | P a g e



45 | P a g e

Annex C: Completion Certificate


46 | P a g e



47 | P a g e


48 | P a g e


49 | P a g e


50 | P a g e



51 | P a g e

Annex D: ESMF OK Card


52 | P a g e



53 | P a g e


54 | P a g e


55 | P a g e

Annex E: Third-party Test Results


56 | P a g e



57 | P a g e


58 | P a g e



59 | P a g e

Annex E: Photographs Before and

After Rehabilitation Works


60 | P a g e



61 | P a g e

Stilling Basin Baffle Blocks – Before & During Construction


62 | P a g e


63 | P a g e


64 | P a g e

Stilling Basin Baffle Blocks – After


65 | P a g e


66 | P a g e

Upstream Face – Before

Upstream Face – During


67 | P a g e


68 | P a g e

Upstream Face – After


69 | P a g e

Repair of RBC – During


70 | P a g e


71 | P a g e


72 | P a g e


73 | P a g e


74 | P a g e

Repair of RBC – After

Reaming of porous holes


75 | P a g e


76 | P a g e


77 | P a g e

Annex F: DBA and Inundation Maps


78 | P a g e


1. INTRODUCTION

1.1: Preface:

Karnataka Engineering Research Station is a premiere Research Institute under

Water Resources Department, Government of Karnataka. The Research Station was

entrusted with the dam break analysis and preparation of inundation maps for Emergency

Action Plan of Kabini Dam by the Project Authorities.

The necessary training and inputs for dam break modeling have been provided by

CWC under DRIP. The required information and details of the Kabini dam have been

provided by the Project Authorities.

A draft report comprising dam break analysis of Kabini Dam and inundation

mapping for different scenarios was submitted to CWC for review, for which some

comments and suggestions were received from the review committee vide letter no.

5213/10.11.2017 (enclosed vide Annexure-2).

Further, the Deputy Director, CWC, New Delhi had directed to depute the

concerned officers of KERS to CPMU (DRIP), New Delhi for modification and finalization

of the Kabini Dam Break Analysis (letter enclosed vide Annexure-3). As per the

instructions of CPMU (DRIP), New Delhi, the Kabini Dam Break analysis Model were

modified and resubmitted for approval. The approval of the Kabini Dam Break Model by

CPMU (DRIP) was sent through mail and the same is attached vide Annexure-4. The

present report has been prepared incorporating all the recommendations/suggestions of

CPMU(DRIP), New Delhi.

1.2: General:

Based on the type of dam and conditions of the dam site, a dam may fail due to

multiple causes. In addition, the breach shape and timing of a dam failure varies with the

type of dam under consideration. Concrete gravity dams may suffer a partial breach with

the failure of one or more monolith sections. Concrete arch dams may fail suddenly and

completely within a few minutes. Embankment dams do not fail completely or suddenly

as their concrete counterparts. Breaching action in an earthen embankment dam

continues to the point where the reservoir is depleted completely or to the point where

the breached materials resist erosion, such as the dam foundation. The most common

cause of dam failure is flood or dam overtopping. The next common cause is piping or

seepage.

79 | Page

1.2.1: Overtopping Failure:

Overtopping due to large inflow flood is the most common failure mode for

embankment dams. It occurs when the water surface elevation in the reservoir exceeds

the height of the dam. The flow of water over the crest of the dam, an abutment, or a low

point in the reservoir rim follows as a consequence. The foundation and abutments of a

concrete dam may also be eroded due to overtopping, leading to loss of support and

failure due to sliding or overturning. For embankment dams, the failure begins at a

downstream location, with head cutting progressing upwards gradually. As it reaches the

dam top, the width of the dam crest is eroded fast, before the reduction in height starts

taking place. This proceeds at a fast rate and may include the phase of maximum outflow

for a reservoir with capacity small compared to its height. In this phase, the earthen dam

without a core behaves mostly like a sharp crested weir.

The opening created by erosion expands gradually, almost in the shape of a

trapezoid. As the height is reduced to the foundation level, outflow may continue for a

long time if the reservoir is of sufficiently large capacity. For such cases, the peak rate of

outflow is also expected to occur during this phase. The flow mostly resembles the

overflow pattern observed over a broad crested weir with long crest.

1.2.2: Piping Failure:

Piping occurs when concentrated seepage paths develop within an embankment

dam. The seepage slowly continues to erode the dam embankment or foundation, leaving

behind large voids in the soil. Piping begins near the downstream toe of the dam and

works its way towards the reservoir upstream. Erosion proceeds at a more rapid rate as

the voids become larger and larger. As the erosion reaches the reservoir upstream, it

may enlarge and cause total failure of the dam. The process of internal erosion and piping

may be broken up into four phases: initiation of erosion, continuation of erosion,

progression to form a pipe and ultimately, the formation of a breach. Piping failures occur

in earthen dams only. Once such a pipe connection is formed, it is almost impossible to

save the dam from failure.

1.2.3: Large Controlled Releases:

Flood risks at locations downstream of the dam may also arise without any failure

of the dam and its components. After construction of a dam, the safe carrying capacity of

the river channel normally keeps on decreasing, due to the diversion of water as well as

flood moderation by the reservoir. Consequently, after many years of dam construction,

80 | Page

the river channel downstream of a dam loses its capacity to carry the peak flood

magnitudes. So, extensive bank overflows become associated with flood discharges. The

situation gets further aggravated due to developmental activities taking place in the

floodplain because of reduced frequency of inundation.

In the event of a severe flood in the dam catchment having a magnitude of peak

discharge near to the design flood of the dam, the priority of dam operation will shift to

saving the dam. Otherwise, a dam breach may endanger the lives of many more persons

residing in the downstream area. With the passage of flood flows near to the spillway

capacity, severe floods causing huge inundation may occur. It may even lead to loss of

lives which has to be minimised through implementation of strict floodplain regulatory

management plans and flood warning.

1.3: Objectives:

• The main purpose of the study is to find out the areas downstream of Kabini Dam

which will be inundated due dam breach scenarios such as overtopping and non-

flood failure (piping) and to find out the inundation scenario in case of large

controlled release.

• To estimate the number of villages and people at risk due to dam failure and large

controlled release.

• To assess the submergence of infrastructure facilities such as roads and railways.

• To prepare the inundation maps for the breach scenarios such as overtopping and

piping and for controlled large release.

1.4: Scope:

• The scope of the study is restricted to failure of the dam due to overtopping and

piping only. However, inundation maps are prepared for both the cases of failure

and for large controlled releases. No other failure scenarios such as landslide,

earthquake, malfunction of gates and planned removal are considered in this study

because the HEC-RAS software cannot simulate these conditions.

• A tier-2 approach to dam breach and inundation mapping are followed which is an

intermediate level of analysis using medium resolution terrain data. A tier 3

approach to dam breach analysis could be carried out using high resolution LIDAR

data.

81 | Page

2. DESCRIPTION OF KABINI DAM

The Kabini Dam is located at Beechanahalli, near H.D. Kote, Mysore District,

Karnataka State with Lat 110 56’ 27” N and Long 76020’17” E and with a catchment area

of 2142 Sq.Km. The gross capacity of reservoir is 19.52 TMC. Kabini dam is a composite

dam with central masonry overflow section and non-overflow section and left and right

earthen embankment. It caters to the needs of around 22 villages and 14 hamlets and

also serves as a prominent source of drinking water to Bengaluru. Further significant

amount of water is discharged to the Mettur reservoir in Tamilnadu to fulfill the state's

needs. The salient features of Kabini dam is as given below;

Table 2.1: Salient features of Kabini dam

Name of the Project Kabini Reservoir Project

Type of Project Multi-Purpose Project

Name of Dam Kabini Dam

Location of Dam Near Beechanahalli-Bidarahalli Village, H.D.Kote Taluk, Mysore District

Name of River Basin location Cauvery basin

River Tributary Kabani, Papanashini and Panamarum Puzha

of Kerala

Latitude 11056’27” N

Longitude 76020’17” E

Catchment Area 2141.90 Sq.Km

Gross storage capacity 19.52 TMC

Live Storage 19.19 TMC

Dead storage 0.33 TMC

Lowest Foundation Level (ft) RL 2110.00

River Bed Level (ft) RL 2204.00

Crest Level (ft) RL 2244.00

Full Reservoir Level (ft) RL 2284.00

Maximum Water Level (ft) RL 2284.00

Top of the Dam (ft) RL 2299.00

Maximum Water Spread Area at FRL 64.03 Sq.Km

Type of Dam Masonry gravity dam with overflow and non- overflow sections with earthen flanks on either side

Total length of dam 8965 ft

Length of left non-overflow section 250 ft

82 | Page

https://en.wikipedia.org/wiki/Bangalore

https://en.wikipedia.org/wiki/Mettur_Dam

https://en.wikipedia.org/wiki/Tamil_Nadu

Length of overflow spillway section 265 ft

Length of power dam 70 ft

Length of right non-overflow section 250 ft

Length of left earthen bund 5805 ft

Length of right earthen bund 2325 ft

Height of the dam above the average

river bed level

90 ft

Maximum base width at foundation

level – overflow section

135.19 ft

Maximum base width at foundation

level – Non-overflow section

155 ft

Top width of road way 24 ft

Drainage gallery size 5 ftX7.5 ft

Designed flood intensity 1,94,150 Cusecs

Discharging length of spillway 160 ft

Maximum flood lift 40 ft

Energy dissipation Hydraulic jump type stilling basin

Spillway crest Ogee section

Crest gates 4 Nos, Radial gates of size 40 ft X 40 ft

River Sluices 3 Nos, of size 8 ft X14 ft

83 | Page

Figure 2.1: Longitudinal section of the masonry spillway portion of the Kabini Dam

84 | Page

Figure 2.2: Cross-section of spillway portion of the Kabini Dam

Figure 2.3: Typical Cross-section of right bank embankment

85 | Page

3. DAM BREACH ANALYSIS

3.1: Model Selection:

HEC-RAS software is used for the dam breach analysis of Kabini Dam. 2D modeling

approach was adopted because of its simplicity when compared to 1D modeling and the

advantages of 2D modeling with 1D modeling is enumerated below;

• 2D modeling can perform 1D, 2D and combined 1D and 2D modeling. In the

present study 2D flow areas were created which were directly connected to 1D

storage with a hydraulic structure.

• There is also an option of choosing either Saint Venant or diffusion wave

equations.

• The 2D flow area can start completely dry and handle sudden rush of water into

the area.

• The algorithm can handle subcritical, supercritical and mixed flow regimes.

• The computational meshes can be both unstructured and structured.

• The detailed hydraulic table properties for 2D computational cells and cell faces

are computed.

• Detailed flood mapping and flood animations are obtained

The limitations to the 2D modeling approach are less flexibility in adding internal

hydraulic structures; cannot perform sediment transport erosion/ deposition; cannot

perform water quality modeling and cannot connect pump stations to 2D flow area.

3.2: Dam Breach Scenarios:

The following three dam breach scenarios are considered in the study;

1. A dam failure caused by overtopping from the inflow design flood leading to

breaching and uncontrolled flow of impounded water.

2. A dam failure caused by internal erosion (piping) with the reservoir at FRL leading

to breaching and uncontrolled flow of impounded water.

3. A large controlled-release flood with IDF and without dam failure.

The hazard potential will be at its maximum when there is a dam breach failure

due to overtopping, downstream hazards due to a dam failure because of piping or even

86 | Page

passage of high discharge (design spillway capacity) through the spillway gates may

sometimes be hazardous. The sudden release of water of even lesser magnitude from a

dam without proper warning may also cause loss of life and property.

3.3: Study Area Boundaries

The study area boundaries are limited to an extent of 160 km downstream of the

Kabini dam where in the flow gets restricted to the natural channel i.e., the total outflow

in the downstream end of the model is within the channel carrying capacity of the main

stream.

3.4: Data Inputs for the Hydraulic Model

3.4.1: Elevation Data:

The Shuttle Radar Topographic Mission (SRTM) 1 Arc-Second Global elevation

data is used in the study which offers worldwide coverage of void filled data at a resolution

of 1 arc-second (30 meters) and provides open distribution of this high-resolution global

data set through USGS website. The elevation data is in Georeferenced Tagged Image

File Format (GeoTIFF) which is a TIFF file with embedded geographic information. This

is a standard image format for GIS applications. File size is approximately 25 MB for 1-

arc-second data files and approximately 3 MB for 3-arc-second data files.

Table 3.1: The product specification of SRTM Elevation data

Projection Geographic

Horizontal Datum WGS84

Vertical Datum EGM96 (Earth Gravitational Model 1996)

Vertical Units Meters

Spatial Resolution 1 arc-second for global coverage (~30 meters)

Raster Size 1 degree tiles

C-band Wavelength 5.6 cm

87 | Page

Figure 3.1: Digital Elevation Model of the Study Area

3.4.2: Land Use Land Cover Data:

GlobCover 2009 landcover map from European Space Agency (esa) is used as

the input to land cover data. The land cover map is derived by an automatic and

regionally-tuned classification of a time series of global Medium Resolution Imaging

Spectrometer (MERIS) Fine Resolution (FR) mosaics for the year 2009. The global land

cover map counts 22 land cover classes defined with the United Nations (UN) Land Cover

Classification System (LCCS). The reference ellipsoid is WGS 84, with pixel resolution of

1/360o.

Figure 3.2: Land Use Land Cover Map of the Study Area

88 | Page

Table 3.2: The Land use Land cover Classes

LULC Code

Land use and land cover type

11 Post Flooding or irrigated croplands

14 Rain fed croplands

20 Mosaic Cropland (50-70%)/Vegetation (G,S,F) (20-50%)

30 Mosaic Vegetation (G,S,F) (50-70%)/Croplands(20-50%)

40 Closed to Open Broadleaved evergreen/semi-deciduous forest

50 Closed broadleaved deciduous forest

70 Closed needle leaved evergreen forest

100 Closed to open mixed broadleaved & needle leaved forest

110 Mosaic Forest/Shrub land (50-70%)/Grassland

120 Mosaic Grassland

130 Closed to open shrubland

140 Closed to open grassland

190 Artificial surface and associated areas

210 Water Bodies

3.4.3: Population Data:

The estimated population for each settlement as per 2011 census was obtained

from data.gov.in portal. However, the present population in each of these settlements

needs to be ascertained. The village-wise population data hosted in the site is having all

the demographic information as per the 2011 census.

3.4.4: Hydraulic Data:

The Kabini Dam has four radial gates of size 40’x40’ with ogee spillway. The crest

level of the gate is 683.97 m. The weir width considered is 7.315 m with an elevation of

700.735 m. The length of the weir 2732.5 m. The discharge co-efficient for weir is taken

as 1.44 considering it as broad crested weir whereas for the ogee weir the weir co-efficient

is taken as 2.21. The radial gate flow parameters considered are radial discharge co-

efficient as 0.6, trunnion exponent as 0.16, opening exponent as 0.72, head exponent as

0.62 and trunnion height as 5.029 m.

3.4.5: Hydrologic Data:

The dam classification system in India depends on the static head and gross

storage capacity of the reservoir. The Kabini dam is classified as large dam as per IS:

11223 (1985) “Guidelines for Fixing Spillway Capacity”.

89 | Page

Table 3.3: Existing dam classification for inflow design flood selection (IS:11223 - 1985)

Class Gross storage capacity (Mm3)

Static head (m) Inflow Design Flood (IDF)

Small 0.5 to 10 7.5 to 12 100-year flood

Intermediate 10 to 60 12 to 30 Standard Project Flood (SPF)

Large > 60 > 30 Probable Maximum Flood (PMF)

3.4.5.1: Methodology of estimating the Inflow Design Flood:

The Inflow Design Flood (PMF) is estimated using HEC HMS software and the

following steps are adopted;

• Development of catchment map with four sub catchments by processing DEM

using GIS.

• Estimation of the physiographic parameters of the four sub catchments.

• Developments of synthetic unit hydrograph (SUH) for the four-sub catchment as

per CWC FER 3(i).

• Adopting the Project specific 2day PMP design storm for the catchment and

estimating the hourly excess rainfall depth for the required numbers of 12hour

duration bells as applicable, considering the loss rate of 0.3 cm /h. The project

specific 1 day and 2 day PMP values of 45 cm and 70.6 cm as recommended by

CWC are adopted.

• Determining the critical sequences of excess rainfall based on the SUH ordinates

of the catchment

• Computing the direct runoff and design flood hydrograph ordinates by convoluting

the critical sequences of excess rainfall with the ordinates of the SUH as per

procedure narrated in the CWC FER 3(i) considering the base flow as 0.05

cumecs/sq. km.

• The design flood hydrograph thus determined is the PMF inflow hydrograph and

the same is routed through the reservoir.

The catchment area, 2142 Sq.Km of Kabini dam is sub divided into four sub

catchments K1, K2, K3 and K4. The catchment map and geomorphologic characteristics

of each of these sub catchments are given below;

90 | Page

Figure 3.3: Catchment area map of Kabini Dam showing four sub catchments (HEC_HMS)

Table 3.4: Geomorphologic characteristics of sub catchments

Sub catchment K1 K2 K3 K4

Area in Sq.Km 435.08 404.35 622.83 679.74

Length of the Longest stream in Km L 42.21 44.48 59.98 53.94

Centroidal Length in Km Lc 19.65 24.13 27.79 26.72

Equivalent Slope in m/km S 1.49 1.55 2.07 1.45

Table 3.5: Storage Elevation Capacity of Kabini Reservoir

Water level elevation

in the Reservoir (m)

Capacity as per 2010

survey (M. Cum)

Capacity of the Spillway

(m3/s)

685 62.94 72

686 83.41 278

687 108.09 538

688 136.96 854

689 170.03 1225

690 207.30 1650

691 248.77 2131

692 294.43 2667

693 344.29 3259

694 398.35 3905

695 456.61 4607

696.163 (FRL) 529.35 5493

91 | Page

Table 3.6: SUH Ordinates for the Sub Catchments

Time

in hrs

SUH Ordinates

K1 K2 K3 K4

0 0 0 0 0

1 2 1.7 2 5

2 6.2 4.9 5.5 12

3 17 11 12 22

4 41 23 25 36

5 80 47.4 47 57

6 117 77 82 89

7 144 104 118 128

8 153.4 122.2 151 162

9 146.2 127.8 172.3 187

10 128.4 123 178.7 195

11 106 110.6 173.1 188

12 81 94.1 156 172

13 60.8 76.4 136 146

14 43.4 58 113 120

15 30 43.5 92 97

16 20 32.8 72 75

17 13.1 23.4 56 57

18 8.3 16.3 42 44

19 5 11.1 31 32

20 3 7.4 22 23

21 1.8 4.4 15.8 16

22 1 2.2 11.1 11

23 0 1 7.6 7.1

24 0 4.8 4.1

25 2.7 2.1

26 1.5 0.9

27 0 0

Figure 3.4: Synthetic Unit Hydrographs for the Sub Catchments

0

20

40

60

80

100

120

140

160

180

200

0 6 12 18 24 30

Dis

char

ge in

m3 /

s

Time in hrs

SUH of Sub catchments

K 1

K 2

K 3

K 4

92 | Page

Table 3.7: Global Summary Results (HEC-HMS)

Figure 3.5: Varying Elevation and Inflow Outflow Curve

93 | Page

Table 3.8: Routing Table

94 | Page

Table 3.8: Cont..

Table 3.9: Summary Results for the Reservoir

95 | Page

3.5: Model Development

3.5.1: Grid/Mesh Resolution:

The two-dimensional depth averaged model was used in the study. The grid

resolution of 150mx150m was selected and the total cells were 93467. Break lines are

not used in the model.

3.5.2: Roughness co-efficient:

The roughness co-efficient was selected based on the land use land cover of the

study area, which was obtained from European Space Agency’s Globcover map.

Table-3.10: The land use land cover downstream of Kabini dam and

its Manning’s N values

LULC Code

Land use and land cover type Manning’s N value

11 Post Flooding or irrigated croplands 0.034

14 Rain fed croplands 0.060

20 Mosaic Cropland (50-70%)/Vegetation (G,S,F) (20-50%) 0.034

30 Mosaic Vegetation (G,S,F) (50-70%)/Croplands(20-50%) 0.034

40 Closed to Open Broadleaved evergreen/semi-deciduous forest 0.100

50 Closed broadleaved deciduous forest 0.100

70 Closed needle leaved evergreen forest 0.110

100 Closed to open mixed broadleaved & needle leaved forest 0.110

110 Mosaic Forest/Shrub land (50-70%)/Grassland 0.035

120 Mosaic Grassland 0.035

130 Closed to open shrubland 0.070

140 Closed to open grassland 0.034

190 Artificial surface and associated areas 0.400

210 Water Bodies 0.040

3.5.3: Flow and Boundary Conditions:

The initial condition assumed for overtopping failure is the top of embankment dam

level 700.735 m plus 0.3 m (critical depth for overtopping failure), for piping failure the

storage elevation at FRL i.e., 696.16m of the reservoir and for large controlled release

the crest level i.e.,683.97 m of spillway is considered. The boundary conditions for

overtopping failure are lateral inflow hydrograph for the reservoir, elevation-controlled

gates (gates are fully opened) for the storage area connection i.e., dam and normal depth

of 0.001 is assumed for the 2D flow area. However, for the piping failure, only normal

96 | Page

depth and elevation-controlled gates (gates are fully closed) are used as the boundary

condition. For controlled large releases, IDF as lateral inflow, gates opening at a rate of

0.1m/min and the normal depth of 0.001 is considered. The breach progression is

modeled as sine wave progression where, breach grows very slowly at the beginning and

end of development and rapidly in between.

3.5.4: Dam Breach Parameters:

The key parameters for arriving at a dam breach hydrograph are the breach

parameters related to the geometry and timing of the breach formation (e.g., width, depth,

shape, and time of failure). The selection of breach parameters for modelling dam

breaches contain the greatest uncertainty of all aspects of dam failure analysis and

therefore a careful evaluation and understanding of the associated breach parameters is

necessary.

Breaching begins when the reservoir water surface elevation reaches the failure

elevation (above the datum). The formulae for the embankment breach parameters are

Bavg=0.23*Km*(Vw)1/3 & Tf=60×√VW/ gHb2

Where, Bavg = expected value of average breach width in meters

Km= 1.0, for internal erosion failures,1.5, for overtopping failures

Tf = breach formation time in seconds

VW =Volume of water above breach bottom in m³

Hb = Height of breach in meters

g= acceleration due to gravity (Froehlich, 2017a)

The top level of the dam is taken as 700.735 m and the breach bottom level as the

river bed level. The reservoir volume for overtopping is considered to be 871.36 M Cum

at 700.735 m (top level of the dam) and for the piping the capacity at FRL is considered

i.e, 529.35 M.Cum. The breach parameters with 90% confidence interval as obtained

from the breach calculator template provided by CWC are adopted for the dam break

analysis.

The center station considered for the breach is 2125 m from the chainage “0”

measured from the left end of the earthen dam. It is assumed that the right earthen

embankment is more vulnerable for breach as this is a homogenous section when

compared to the left side zoned earthen embankment.

97 | Page

Table 3.11: The Dam breach parameters and expected peak outflow for

Overtopping Failure

Failure Mode Overtopping

FRL 696.163

MWL 700.735

Reservoir Volume (FRL) 529360800

Reservoir Volume (MWL) 871364900

Dam Crest Level 700.735

Breach Bottom Level 671.779

Water Surface Elevation (m) 700.735 Choose Interval

Confidence Failure Mode Coefficient Km 1.3 90 %

Reservoir Volume (m3) Vw 871364900 Min. Max.

Slope Breach z 1 0.27 3.64

Height Breach (m) Hb 28.956

Average Width (m) Baveg 286 143 572

Bottom Width (m) Bbottom 257 135 466

Formation Time (H) Tf 5.42 3.69 7.97

Want to use User-Defined Bottom Width? YES

Bottom Width (user defined) Bbottom* 305

Average Width (user defined) Baveg* 334

EXPECTED PEAK OUTFLOW (GRADUAL BREACH - SEMITHEORICAL&EMPIRICAL)

Top Embankment Width (m) Wtop 7.315

Slope Upstream Zup 3.5

Slope Downstream Zdown 2

Failure Mode Coefficient Kc 1.85

Approach length (m) La 1000

Average Embankment Width (m) Wavg 86.9

Factor Kh Kh 1.21

Height Water (m) Hw 28.956 (95% confidence interval)

Maximum Outflow for Instantaneous Breach (m3/s) Qpmax 64,510 Min. Max

Expected Outflow (m3/s) - Empirical Qp1 60,769 35,310 1,04,585

Expected Outflow (m3/s) – Semi theoretical Qp2 43,455 23,529 80,254

98 | Page

Table 3.12: Dam Breach Parameters and expected peak outflow for

Non-Flood failure (Piping)

Failure Mode Piping

FRL 696.163

MWL 700.735

Reservoir Volume (FRL) 529360800

Reservoir Volume (MWL) 871364900

Dam Crest Level 700.735

Breach Bottom Level 671.779

Water Surface Elevation (m) 696.163 Choose Interval

Confidence Failure Mode Coefficient Km 1 90 %

Reservoir Volume (m3) Vw 529360800 Min. Max.

Slope Breach z 0.6 0.17 2.18

Height Breach (m) Hb 28.956

Average Width (m) Baveg 186 93 371

Bottom Width (m) Bbottom 169 89 308

Formation Time (H) Tf 4.23 2.89 6.19

Want to use User-Defined Bottom Width? YES

Bottom Width (user defined) Bbottom* 192

Average Width (user defined) Baveg* 209

EXPECTED PEAK OUTFLOW (GRADUAL BREACH - SEMITHEORICAL&EMPIRICAL)

Top Embankment Width (m) Wtop 7.315

Slope Upstream Zup 3.5

Slope Downstream Zdown 2

Failure Mode Coefficient Kc 1

Approach length (m) La 1000

Average Embankment Width (m) Wavg 86.9

Factor Kh Kh 1.21

Height Water (m) Hw 24.384 (95% confidence

interval)

Maximum Outflow for Instantaneous Breach (m3/s) Qpmax 35,266 Min. Max

Expected Outflow (m3/s) - Empirical Qp1 23,495 13,652 40,435

Expected Outflow (m3/s) – Semi theoretical Qp2 22,546 12,208 41,638

Ref. (Froehlich,2016)

Average Breach width (Baveg)=0.23*Km*Vw^(1/3),

Formation time (Tf)=60*SQRT(Vw/(9.81*Hb^2))/3600,

Height of breach (Hb)=Dam crest level-Breach bottom level

99 | Page

Table 3.13: Trapezoidal Dam Breach Model Parameters and obtained

Dam Breach Flood Peak Discharges

Breach Parameters Units Dam Failure Mode

Overtopping Piping

Height m 28.956 28.956

Bottom Width m 305 192

Average Side Slope (horz:vert) -- 1:1 0.7:1

Formation Time hrs 6.04 4.58

Obtained Peak Discharge m3/s 37,541 20,325

3.5.5: Calibration and Sensitivity Analysis:

Table 3.14: Data set range for the dam break analysis

(as provided by CWC)

Parameters Min Max

Average Embankment Width (m) Wavg 9.63 250

Volume above breach Bottom (m3) Vw 0.0133 701

Height Water (m) Hw 1.68 77.4

Height Breach (m) Hb 3.66 86.9

Approach flow Width La 40 4100

Measured Peak Discharge Qp 30 65120

Table 3.15: Uncertainty Analysis for overtopping failure

(template provided by CWC)

100 | Page

Table 3.16: Uncertainty Analysis for Non-Flood failure

(template provided by CWC)

101 | Page

3.5.6: Computational Aspects:

Full momentum equation is used for the analysis and the computation interval or

the time step adopted is 1 sec. The percent volume accounting error for the storage and

2D flow area are 0.6986 and 0.0206 for overtopping failure simulation and 0.5094 and

0.02604 for Non-flood failure simulation respectively. There is no convergence error in

both the simulations. In case of large controlled releases, the percent volume accounting

error for the storage and 2D flow area are 0.0097 and 0.0096 respectively.

102 | Page

Figure 3.6: Overtopping Failure Computation Log File

103 | Page

Figure 3.7: Non-Flood Failure (Piping) Computation Log File

104 | Page

Figure 3.8: Large Controlled Release Computation Log File

105 | Page

3.5.7: Peak Discharge Reasonableness:

The reasonableness of the peak discharge downstream of the dam breach is

ascertained by expected peak outflow (gradual breach- semi theoretical and empirical

equations) and the velocity at the time of breach. The calculation template provided by

CWC is used to ascertain expected peak outflow with 95% confidence interval.

3.6: Results:

The simulation results show that the breach velocity for overtopping failure is 3.07

m/s whereas for piping failure it is 3.41 m/s at the time of breach. The peak discharge

obtained for overtopping failure is 37,541 m3/s and for piping failure it is 20,325 m3/s. The

discharge at the end of the downstream boundary is 9514.93 m3/s and 3345.65 m3/s for

overtopping failure and non-flood failure respectively.

3.6.1: Output Hydrograph:

The output hydrograph as obtained after simulation in HEC RAS for overtopping

and non-flood failure are given below;

Figure 3.9: Overtopping Failure Dam Breach Flood Hydrograph

106 | Page

Figure 3.10: Non-Flood Failure (Piping) Dam Breach Flood Hydrograph

3.6.2: Flood Hazard Reference Values/ Population at Risk (PAR) /

Potential loss of life (PLL):

Flood hazard reference values consisting of maximum water depth, maximum

depth-averaged velocity, and flood wave arrival time at various locations downstream of

Kabini Dam, Population at risk as per the 2011 census data and potential loss of life are

presented in Table 3.17. The potential loss of life is approximately estimated based on

the settled area inundated to the total settlement area and then multiplied with the total

population. The Reference values were determined close to the identified positions and

represent the degree of danger that would be created by the flood. The settlements along

the downstream of the Kabini Dam were identified using Google earth.

107 | Page

Table 3.17: Flood Hazard Reference Values

Location

Approximate distance

downstream from the

dam in km

Population at risk as per 2011 census

Potential loss of life

Overtopping Failure Non-Flood Failure Large Controlled

Releases

Max Depth

(m)

Max Velocity

(m/s)

Flood wave arrival time

(hours)

Max Depth

(m)

Max Velocity

(m/s)


(hours)

Max Depth

(m)

Max Velocity

(m/s)

Beechanahalli 0.25 1174 1174 6.42 3.23 0.02 1.65 1.08 2.73 … …

Agathur 0.79 2100 1680 13.04 2.97 0.03 8.70 1.31 0.98 4.15 0.76

Sagare 1.07 3586 897 6.05 1.16 1.27 1.70 0.13 2.32 … …

Nerale 3.42 2692 2154 6.30 1.33 1.80 1.50 0.75 2.90 … …

Magudilu 4.57 1431 716 9.22 1.71 1.75 4.34 1.30 2.70 2.89 0.44

Sargur 6.59 2283 1712 14.04 2.98 1.38 9.13 1.25 2.28 6.18 0.80

Itna 7.88 2410 2169 11.04 1.72 1.95 6.16 1.37 2.98 4.04 1.02

Bidagalu 8.21 200 200 6.50 1.65 2.17 1.61 0.82 3.30 … …

Nilavagilu 10.49 877 395 5.76 2.19 2.70 0.59 0.19 4.27 … …

Thoravalli 12.01 753 377 8.45 2.17 2.33 3.28 1.84 3.38 0.11 0.66

Kothagala 16.96 503 101 7.75 0.26 2.95 2.74 0.14 4.10 … …

Kunnapatna 18.26 310 186 10.48 1.69 2.75 5.75 1.19 3.73 3.23 0.72

Manchahalli 21.14 207 207 10.00 1.89 3.03 5.64 1.02 4.05 1.92 0.52

Hulikura 22.05 120 12 0.99 1.27 5.40 … … … … …

Kulya 24.54 918 275 7.27 2.51 3.82 2.95 1.57 5.08 2.43 1.04

Hebbalaguppe 24.95 3717 1673 14.10 2.70 3.35 9.82 1.73 4.35 7.33 0.95

K Belthur 26.65 2199 2089 10.55 2.35 3.72 5.98 1.05 4.83 4.61 0.51

Matakere 28.22 1697 1188 10.86 2.10 3.95 6.32 1.38 5.10 4.88 0.73

Chakkur 30.82 1848 370 5.96 2.66 5.28 1.60 1.06 7.53 … …

Hyrige 32.23 3716 186 3.00 0.12 5.75 … … … … …

Madapura 1 32.57 2838 1845 8.75 1.69 4.66 … … … 3.01 0.42

Kolagala 33.83 3257 1629 9.43 2.14 5.17 5.11 0.95 6.62 5.18 0.28

Moleyur 35.18 878 18 0.79 0.12 8.03 … … … … …

Holehundi 36.87 300 300 4.35 1.45 6.13 0.02 0.62 11.83 … …

Karigala 39.27 1367 68 4.66 1.72 6.88 … … … … …

Ibjala 39.61 2395 1796 11.47 1.41 5.62 7.24 1.06 7.10 4.42 0.68

108 | Page

Table 3.17 Cont..

Location

Approximate dstance

downstream from the

dam in km




Releases

Max Depth

(m)

Max Velocity

(m/s)


(hours)

Max Depth

(m)

Max Velocity

(m/s)


(hours)

Max Depth

(m)

Max Velocity

(m/s)

Hommaragahalli 41.84 3780 756 6.43 0.21 6.45 2.15 0.11 8.85 1.32 0.04

Jinnahalli 42.66 2045 409 3.93 0.83 7.25 … … … … …

Haradanahalli 43 3231 1292 12.77 2.36 5.93 8.71 1.44 7.48 7.94 1.16

Hirinandi 46.55 554 194 8.51 2.13 7.07 5.05 1.30 9.03 3.72 1.10

Motha 47.09 1062 53 1.95 0.45 8.85 … … … … …

Nellithalapura 49.19 1410 14 2.96 0.19 8.82 … … … … …

Kanenur 49.37 2717 1087 8.39 2.40 7.42 5.03 1.56 9.45 3.51 1.30

Hatwal 52.02 1587 714 5.86 1.31 8.47 1.84 0.52 11.38 1.34 0.14

Kadanahalli 52.98 582 29 1.69 0.05 10.63 … … … … …

Hullahalli 54.31 8794 4397 12.00 2.50 8.20 7.83 2.04 10.42 7.36 1.56

Rampura 56.7 5258 3155 7.66 2.32 8.83 3.57 0.80 11.57 3.14 0.69

Belale 57.68 1388 14 0.12 0.94 15.35 … … … … …

Kembal 59.16 688 275 4.70 1.01 9.93 0.59 0.37 14.73 0.28 0.41

Byalaru 64.55 594 535 5.48 1.13 11.05 1.26 0.33 15.50 … …

Debur 65.92 3286 1314 7.01 1.07 10.95 2.85 0.51 14.47 2.60 0.27

Kallahalli 68.07 1119 336 11.86 3.62 11.67 8.59 2.35 14.93 8.38 2.26

Goddanapura 69.7 1140 228 3.07 0.74 12.97 … … … … …

Yechagalli 70.85 3232 646 7.66 0.67 11.95 3.79 0.25 15.63 3.55 0.20

Tandavapura 71.46 5817 1163 3.66 0.31 12.77 … … … 1.40 0.04

Kathavadpura 72.15 1862 1862 13.45 1.67 11.43 9.63 1.00 14.63 9.40 1.05

Nanjangud Rural 73.02 334324 234027 1.62 0.10 14.72 6.92 3.06 15.30 6.25 2.89

Deveerammanahalli 75.82 8077 81 1.66 0.11 16.55 … … … … …

Thoramavu 78.1 1781 1781 4.32 1.76 12.85 1.98 1.36 16.70 1.88 1.16

Mullur 1 79.54 1628 977 5.03 1.55 13.75 2.06 0.58 17.92 0.84 0.31

Horalavadi 82.6 2752 1651 7.91 2.22 13.60 4.94 1.04 17.58 5.01 1.00

Saragooru 85.93 2283 457 8.02 1.36 14.50 4.63 0.99 18.85 4.87 0.88

Haniyamballi 87.56 843 169 2.92 0.32 16.35 … … … … …

109 | Page

Table 3.17 Cont..

Location


downstream from the

dam in km




Releases

Max Depth

(m)

Max Velocity

(m/s)


(hours)

Max Depth

(m)

Max Velocity

(m/s)


(hours)

Max Depth

(m)

Max Velocity

(m/s)

Hadinaru 88.75 6996 700 2.82 0.48 16.65 … … … … …

Moodahalli 90.63 1960 686 5.63 1.29 15.55 2.02 0.58 20.63 2.35 0.60

Kupparavalli 91.79 1519 911 9.68 1.17 15.22 6.05 0.85 19.85 6.37 0.73

Suthur 92.57 4006 801 9.34 0.85 15.45 5.67 1.33 20.17 6.03 1.20

Alathur 93.15 1677 1006 8.36 1.71 15.57 4.67 1.22 20.35 5.01 1.12

Bilugali 93.69 3122 624 7.50 0.41 16.38 4.07 0.24 21.58 2.42 0.18

Hosakote 94.9 5109 2555 6.26 0.51 16.12 2.56 0.55 21.55 2.91 0.67

Thumnerale 96.07 2509 502 2.72 0.51 17.92 … … … … …

Nandigunda 97.41 907 544 10.27 1.85 16.18 6.93 1.33 21.13 7.27 1.19

Jodihariharapura 99.23 1117 335 5.47 0.80 17.13 2.40 0.41 22.72 3.02 0.42

Yadakola 100.29 5203 1041 4.27 0.89 17.45 1.30 0.47 23.72 1.87 0.48

Thayur 101.16 2742 823 5.18 0.99 17.90 2.13 0.52 23.98 2.46 0.53

Danayanakapura 103.99 1283 257 4.06 1.22 18.35 1.11 0.58 25.15 1.45 0.62

Kiragasur 1 106.48 3033 1365 5.96 1.40 18.42 3.27 0.94 24.33 3.14 0.96

Yadadore 107.11 3395 1019 4.71 1.26 18.95 1.99 0.40 25.20 3.39 0.55

Hunsuru 108.46 1445 1301 5.90 2.26 18.92 3.21 1.23 24.93 3.64 1.40

T.Narsipura 110.35 260159 221135 11.09 2.99 19.08 8.20 2.29 25.03 8.80 2.24

Kethahalli 111.35 2798 560 4.71 0.23 20.30 1.82 0.12 27.73 2.40 0.11

Algodu 111.35 6911 5183 7.77 0.98 19.48 4.88 0.70 25.67 5.19 0.72

Binakanahalli 112.55 3511 1053 4.76 1.03 20.73 1.56 0.36 28.58 2.28 0.55

Chowhalli 113.77 1245 747 4.29 1.32 20.83 1.30 0.50 28.82 1.92 0.69

Gargeswari 114.13 5343 2672 5.32 0.62 20.00 2.28 0.11 27.17 2.94 0.22

Nilasoge 114.95 2852 285 2.99 0.72 22.02 … … … … …

S Megadahalli 115.43 2211 332 1.76 0.25 23.45 … … … … …

Muthalavadi 116.14 2821 141 2.50 0.63 22.82 … … … 0.04 0.16

Hosapura 116.14 764 76 2.64 0.52 22.47 … … … … …

110 | Page

Table 3.17 Cont..

Location


downstream from the

dam in km




Releases

Max Depth

(m)

Max Velocity

(m/s)


(hours)

Max Depth

(m)

Max Velocity

(m/s)


(hours)

Max Depth

(m)

Max Velocity

(m/s)

Hiriyur 117.43 1874 375 6.36 0.65 21.12 3.27 0.21 28.00 3.92 0.21

Madapura 2 117.85 2325 698 1.26 0.37 24.81 4.15 0.76 6.05 0.64 0.28

Karagahalli 119.27 1924 385 3.64 0.34 22.58 0.48 0.11 32.62 1.15 0.09

Doddabbagilu 120.49 4497 450 2.20 0.06 25.08 … … … … …

Akkur 121.94 1683 505 4.09 1.11 23.17 0.54 0.33 33.87 … …

Hemmige 125.61 3960 1386 3.99 0.95 24.83 … … … 1.08 0.09

Vodavandanahalli 126.58 1134 57 1.54 0.67 27.45 … … … … …

T Doddapura 129.74 2520 630 4.77 0.80 25.63 1.59 0.27 35.37 2.51 0.34

Talakad 130.65 8539 1281 3.95 1.37 26.25 1.40 0.36 36.20 2.13 0.51

Hosamalangi 133 2453 1227 6 0.52 25 2.40 0.14 34.28 3.32 0.19

Malangi 134.25 2320 1160 9.68 1.37 24.43 6.82 0.81 31.73 4.69 0.83

Kaliyur 135.99 3718 558 5.43 0.68 28.15 2.24 0.07 40.57 3.22 0.13

Kunthur 138.21 4094 1228 2.40 0.17 30.38 … … … … …

Teramballi 139.04 2256 564 2.32 0.61 30.38 … … … 0.17 0.05

Agara 139.04 2866 1003 2.07 0.16 32.35 … … … … …

Mullur 2 140.32 5761 4033 5.03 0.66 27.16 … … … 2.80 0.50

Uttamballi 140.32 1959 1371 3.88 0.72 29.38 0.89 0.31 40.38 1.61 0.51

Kollegal 143.47 289638 86891 5.57 0.63 28.58 2.22 0.27 37.32 3.13 0.33

Hampapura 144.41 3116 3116 4.55 0.95 28.78 1.25 0.50 38.57 2.12 0.58

Harale 145.75 2544 1018 4.34 0.95 29.60 1.01 0.61 40.05 1.90 0.61

Holesalu 148.19 5179 777 2.50 0.44 32.73 … … … 1.23 0.53

Saragoor 149.28 1820 273 1.54 0.51 34.22 … … … … …

Madavadi 152.24 738 7 1.77 0.32 34.47 … … … … …

C M Samudra 152.94 600 300 4.91 1.59 30.90 2.53 1.42 39.25 1.37 1.69

Kiragasur 2 154.29 1168 175 1.54 0.38 35.11 … … … 0.26 0.09

Sathegala 155.42 13074 654 3.16 1.06 32.97 0.29 0.20 46.95 0.15 0.46

Belakavadi 155.42 9151 183 1.31 0.32 35.45 … … … … …

111 | Page

Figure 3.11 Graph Showing Flood Hydrograph at Different Locations Downstream of Kabini Dam for Overtopping Failure

0

5000

10000

15000

20000

25000

30000

35000

40000

20-03-2018 00:00 20-03-2018 12:00 21-03-2018 00:00 21-03-2018 12:00 22-03-2018 00:00 22-03-2018 12:00

Flo

od

in C

um

ecs

Time in hours

FLOOD HYDROGRAPHS AT DIFFERENT LOCATIONS DOWNSTREAM OF KABINI DAM (Overtopping Failure)

0.8 km 5.5 km 11.5 km 19 km 25 km

32 km 37 km 44 km 57 km 71 km

85 km 96 km 110 km 136 km 161 km

112 | Page

Figure 3.12 Graph Showing Flood Hydrograph at Different Locations Downstream of Kabini Dam for Non-Flood Failure

0

5000

10000

15000

20000

25000

22-03-2018 00:00 22-03-2018 12:00 23-03-2018 00:00 23-03-2018 12:00 24-03-2018 00:00 24-03-2018 12:00 25-03-2018 00:00 25-03-2018 12:00

Flo

od

in C

um

ecs

Time in hours

FLOOD HYDROGRAPHS AT DIFFERENT LOCATIONS DOWNSTREAM OF KABINI DAM(Non-Flood Failure)

0.8 km 5.5 km 11.5 km 19 km 25 km

32 km 37 km 44 km 57 km 71 km

85 km 96 km 110 km 136 km 161 km

113 | Page

4. FLOOD INUNDATION MAPPING

An Emergency Action Plan (EAP) is a formal document that identifies potential

emergency conditions at a dam and specifies pre planned actions which are required to be

followed for minimising damage to proper-ties and loss of life. The EAP specifies actions for

the dam owner, in coordination with emergency management authorities, to be taken while

responding to incidents or emergencies related to the dam. It presents procedures and

information for assisting the dam owner in issuing warnings and notification messages to

responsible downstream emergency management authorities. The EAP includes inundation

maps for assisting the dam owner and emergency management authorities in identifying

critical infrastructure and sites with huge population at risk, which may require protective

measures and warning as well as evacuation planning.

Inundation maps showing

1) Maximum water depth in m

2) Maximum water velocity in m/s

3) Maximum water-surface elevation in m-MSL and

4) Flood wave arrival time are prepared for each of the three flood scenarios

considered.

Flood Inundation maps for the parameters mentioned above were prepared using Arc

GIS software. The Scale of the map is 1:50,000. The total length of inundation downstream

of Kabini Dam of about 160 km has 9 tiles per scenario. The projection type is WGS-84 UTM

zone 43 N. The settlement layer is obtained by digitising the settlement boundary from

google earth. The rail and road layer from open source DIVA-GIS are used for mapping. The

village maps were obtained from projects.datameet.org (data meet is a community of data

science and open data enthusiasts) with WGS-84 format.

114 | Page

5. CONCLUSIONS

• Kabini dam has high hazard potential due to huge storage capacity and significant

habitation in the downstream.

• The Kabini dam break analysis is carried out for tier 2 approach using medium

resolution terrain data.

• About 106 villages are found to be affected in case of Kabini dam breach.

• The people living in villages with in 1 km downstream of Kabini dam are most

vulnerable as the flood wave arrival time is less than 2 minutes in case of overtopping

failure.

• The peak breach flow obtained is 37,541 m3/s and 20,325 m3/s for overtopping and

piping failure respectively.

• The breach velocity at the time of failure is 3.07 m/s and 3.41 m/s for overtopping

failure and piping failure respectively which are well within the recommended limits.

• It is observed that the inundation on both sides of the river is significant in case of

flood due to large controlled release.

• At a distance of approximately 160 km from the dam site, it is observed that the flood

water will be confined to the river course.

• The inundation maps are developed to a scale of 1:50,000 which are readily printable

on A-3 size paper. However, they can be printed on to bigger size paper for better

readability.

• The developed inundation maps are useful for preparation of EAP (Emergency Action

Plan).

115 | Page

References

1. TD-39 Using HEC-RAS for Dam break studies, August 2014, US Army Corps of

Engineers, Hydrologic Engineering Center.

2. CPD-68A; HEC-RAS River Analysis System 2D Modeling User’s Manual, Version

5, Feb 2016.

3. Doc.No. CDSO-GUD-DS-05-VI.0 Guidelines for Mapping Flood Risks Associated

with Dams January 2018, CWC, MOWR, River Development and Ganga

Rejuvenation, GOI.

4. Flood Estimation report for Kaveri basin sub zone- 3(i) including Palar and

Ponnayyar rivers but excluding eastern coastal region, a method based on unit

hydrograph principle, Design office report no. CB/11/1985, Hydrology (small

catchments), Directorate CWC, New Delhi, Jan 1986.

5. An Empirical Model of Embankment Dam Breaching by David C Froehlich, third

National Dam Safety Conference 18-19 Feb 2017, Roorkee, India.

6. Embankment Dam Breach Parameters and their Uncertainties by David C

Froehlich, Journal of Hydraulic Engineering, Dec 2008.

7. Manual on Estimation of Design Flood by CWC, New Delhi Mar 2001.

8. Predicting Peak Discharge for gradually breached embankment dam, by David C

Froehlich, Journal of Hydrologic Engineering, July 2016.

9. IS 11223-1985 (RA-1995), Guidelines for fixing spillway capacity.

10. CPD-74A; Hydrologic Modeling System HEC-HMS, User’s Manual version 4.2,

Aug 2016 by US Army Corps of Engineers, Hydrologic Engineering Center.

116 | Page

project rehabilitation report of kabini dam,

Documents