IUKWC Workshop November 2016: Developing Hydro-climatic Services for Water Security Session 3.5 Pankaj Mani

1. Incorporating Climate Change Impacts in Estimating
Design Basis Flood Level at a Project Site
Pankaj Mani
(mailofpmani@yahoo.com)
National Institute of Hydrology,
Patna

2. Climate Change impacts on Water
Resources Projects
• Design flood hydrograph is a key input for Water
Resources Projects particularly flood protection/
management works.
• The design flood is computed by convoluting design storm
with unit hydrograph.
• The general prediction from climate change research
indicates comparatively more vigorous hydrological cycle
resulting into
– increased precipitation (intense storm with altered temporal
distribution)
– Increased evaporation rates
• This in turn affect the design storm and further the design
flood and then the maximum flood level

3. % increase in peak of flood
hydrograph with % increase in peak
of UH

4. % decrease in peak of flood
hydrograph with loss rate

5. Design storm distribution patterns

6. Sc-1 98 yrs data (base run)
Sc-2 Highest 20% increased by 5%
Sc-3 Highest 20% increased by 5%
Lowest 20% decrease by 5%
Sc-4 Highest 20% increased by 20%
Sc-5 Highest 20% increased by 20%
Lowest 20% decrease by 20%

7. Return Periods 25 50 100 1000
Scenario 1 8978 10418 12042 19208
Scenario 2 9403 11049 12945 21676
Scenario 3 9408 11025 12868 21186
Scenario 4 10603 12896 15657 29802
Scenario 5 10685 12842 15358 27317
Return Periods 25 50 100 1000
Scenario 2 4.73 6.05 7.50 12.85
Scenario 3 4.78 5.83 6.86 10.30
Scenario 4 18.0 23.8 30.0 55.2
Scenario 5 19.0 23.3 27.5 42.2

8. PMF
6842
m3/s
1.05 PMP 1.10 PMP 1.15 PMP 1.20 PMP
Peak of PMF
7064 7401 7737 8073
% Deviation in PMF
3 8 13 18

9. 9
• Breach in FBC
• Breach in BML
• Catchment flooding
• Local site rainfall
Effect of climate change on maximum flood
level at a plant site
Case Study: NPCIL, Harayana

10. ~14.7%
~14.85

11. 11
Rainfall estimate is increased
by 15% to account for the
future climate change
The maximum flood level is
computed as RL 218.25 m
which was otherwise RL
218.15 m.
An increase of 0.1 m is
computed due to increase in
rainfall estimate by 15%
Effect of climate change on maximum flood
level at a plant site

12. 12
DBE

13. 13178 ha additional area is flooded
DBE +CC

14. Effect of climate change on maximum flood
level at a plant site
Various sources of flooding:
Upstream catchments floods
Back water effect of Bargi dam
Failure of upstream dams
Local site rainfall

15. 15
The impact of climate change has been considered by increasing the rainfall
by 15% and thus the corresponding river flow is computed and its effect on
flooding has been estimated as 2.02 m.
Effect of climate change on maximum flood
level at a plant site