1. EXTRAPOLATION OF RATING CURVE WHY: –GAUGING DOES NOT COVER FULL RANGE OF FLOW –CALIBRATION AT HIGH FLOW IS DIFFICULT: *OCCURS INFREQUENTLY *SHORT DURATION –AT HIGH STAGES A DIFFERENT CONTROL MAY EXIST (FLOODPLAIN, DIFFERENT ROUGHNESS) WHERE: –EXTRAPOLATION AT STATE DATA PROCESSING CENTRE OHS - 1

2. HIGH FLOW EXTRAPOLATION METHODS: –DOUBLE LOG PLOT METHOD –STAGE-AREA/STAGE-VELOCITY METHOD –THE MANNING’S EQUATION APPROACH –THE CONVEYANCE SLOPE METHOD OHS - 2

3. DOUBLE LOG PLOT METHOD CONDITIONS: –HYDRAULIC AND GEOMETRIC CHARACTERISTICS DO NOT CHANGE BEYOND MEASURED RANGE IMPLICATION: –POWER TYPE RATING CURVE FITTED TO THE LAST (HIGHEST) SEGMENT WILL BE CONSIDERED APPLICABLE TO EXTRAPOLATED RANGE AS WELL OHS - 3

4. X-SECTION KHAMGAON, 1997 OHS - 4

5. OHS - 5

6. STAGE-AREA/STAGE-VELOCITY METHOD USE: –TO EXTRAPOLATE RATING CURVE BEYOND MEASURED RANGE BASED ON: *MEASURED STAGE-X-SECTIONAL AREA RELATION *EXTRAPOLATED STAGE-VELOCITY PLOT NOTE: –ASSUMPTION IS THAT STAGE-VELOCITY PLOT CAN EASILY BE EXTRAPOLATED SINCE RATE OF INCREASE OF VELOCITY AT HIGHER STAGES DIMINISHES RAPIDLY –FROM A HYDRAULIC POINT OF VIEW ASSUMPTION DOUBTFULL SINCE U::R^2/3 OHS - 6

7. ILLUSTRATION OF STAGE- AREA/STAGE-VELOCITY METHOD OHS - 7

8. MANNING’S EQUATION METHOD METHOD –K* = f(h) PLOTTED FROM DISCHARGE MEASUREMENTS –K* BECOMES APPROX. CONSTANT FOR h>> –K* WITH A r AND R r FROM MEASUREMENTS EXTRAPOLATED –FLOOD PLAIN TREATED BY MANNING EQUATION –S CAN BE ESTIMATED FROM TOPOSHEETS OHS - 8

9. MANNING’S EQUATION METHOD OHS - 9

10. OHS - 10

11. OHS - 11

12. OHS - 12

13. CONVEYANCE-SLOPE METHOD METHOD: –CONVEYANCE AND ENERGY SLOPE ARE EXTRAPOLATED SEPARATELY –A AND R FROM FIELD SURVEY –Km ESTIMATED IN FIELD –K EXTRAPOLATED –S FOLLOWS FROM (Q/K) 2 VERSUS h –EXISTING S-TENDENCY EXTRAPOLATED OHS - 13

14. OHS - 14

15. OHS - 15

16. INTERPRETATION OF WETTED PERIMETER FLOOD PLAIN RIVER OHS - 16

17. EXTRAPOLATION WITH HYMOS FIRST: –COMPUATATION OF GEOMETRIC AND HYDRAULIC QUANTITIES IN MEASRED RANGE NEXT: –PLOT OF FOLLOWING PARAMETERS AS f(h) *SURFACE WIDTH *WETTED PERIMETER *X-SECTIONAL AREA * HYDRAULIC RADIUS *AR 2/3, Q, u, conveyance K, AND S FINALLY: –K EXTRAPOLATED AND S ASYMPTOTICALLY EQUAL TO BEDSLOPE: Q = KS 1/2 OHS - 17

18. OHS - 18

19. OHS - 19

20. OHS - 20

21. OHS - 21

22. OHS - 22

23. OHS - 23

24. OHS - 24

25. OHS - 25

26. OHS - 26

27. OHS - 27

28. OHS - 28

29. OHS - 29

30. OHS - 30