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Climate Change and Sustainable
Floodplain Management
Dr. K. B. Sajjadur Rasheed
Former Professor of Geography and Environment,
University of Dhaka
Adjunct Faculty, Independent University, Bangladesh
and
Consultant, Center for Environmental & Geographic
Information Services
Disaster and Floodplain Management: DRTMC,
University of Dhaka
Prologue
20th century’s biggest challenge is
climate change
and its biggest threat is to
‘environment’ and ‘sustainable
development’
Floodplains are a dynamic landscape:
their forms and features are continually
changing; hence, sustainability is a
major goal
Climate Change Impacts and Projections
 Observed impacts:
 Atmospheric warming is unequivocal
 Each of the last three decades has been
successively warmer than any decade since
1850
 Over the past two/three decades, glaciers
and ice sheets have continued to shrink
 Between 1993 and 2010, mean annual sea
level rise [globally] was 3.2 mm
continued
 Projected impacts:
 Continued emission of GHGs will cause further
warming, and is likely to exceed 2oC by 2100
 Virtually certain that there will be more heat waves
 Monsoon precipitation: likely to increase
 Monsoon retreat dates: likely to be delayed
 By 2100, global glacier volume likely to decrease by
15 to 85 percent
 SLR – likely to be up to 0.82 meters with no
mitigation; and will continue beyond 2100
Significance in BD ecosystem
 Higher temp means more moisture from
BoB; more rain internally & in
India/Nepal/Bhutan; more water volume in
GBM rivers; and higher frequency of floods
 Forms & features of floodplains will undergo
continuous changes; due to floods [area,
depth, duration], bank erosion and high
intensity rain
continued
 Adverse impacts on floodplain livelihoods:
 Farmland submergence: crop loss
 Prolonged drought: land degradation
 Delayed monsoon retreat: threat to
Kharif II (T. aman) and Boro crops
 Salinity in coastal zone: crop loss
 Loss to fisheries sector from flooding
 Biodiversity health: trees and species habitat
What is ‘sustainability’ in floodplain
management?
 Use & maintaining floodplain ecosystem over the
generations
 Floodplain is dynamic: changes in it are intensified
from climate change impacts
 Soils are reformatted; drainage is altered; farmlands
are reclassified; settlements and other infrastructure
are relocated due to floods and bank erosion
 Task: efforts to contain damage and retain basic
potentials for farming, fishing & settlements
 Objective is to make floodplains capable to meet the
needs of growing population for more crops, more
homesteads, more fisheries, more biodiversity etc.
Response Strategy and Options for
Floodplain Management
Adaptation and Disaster Risk Reduction
Adaptation: seeks to make adjustments
in natural and human systems to
impacts caused or will be caused by
climate change: [autonomous or
planned]
DRR: efforts to reduce damage through
mitigating disaster effects AND
preparedness to meet the challenge
continued
Both adaptation and DRR should go in
tandem since climate change related
hazards are going to be more frequent
and intensive; and DRR can help in
(a) preventing or avoiding, (b)
minimizing losses; and (c) recovery
Preparedness under DRR strategy is a
major instrument for sustainability of
floodplains
continued
Response planning in Bangladesh
National Adaptation Program of Action
[NAPA]: 2009 (updated version of 2005)
Bangladesh Climate Change Strategy
and Action Plan [BCCSAP]: 2009
Both documents address problems of
livelihood security and sustainability
for floodplains, where most people live
continued
 Both documents (especially BCCSAP)
emphasize measures for floodplain
ecosystem, such as
(a) innovative crop technology with climateresilient crops; (b) diversification of fish
culture techniques; (c) strengthening flood
and cyclone warning systems; and (d) repair,
rehabilitate existing embankments and plan,
design & construct new hazard mitigation
structures like river embankment, coastal
embankments, and drainage systems etc.
Measures to ensure floodplain
sustainability
 Principal objective is to enhance the
resilience of floodplains to face:
 increased rainfall & flooding and more
volume of upstream water;
 management of channel siltation,
 bank erosion;
 soil salinization;
 land degradation from drought;
 vulnerability of settlements & infrastructure
from inundation
Embankments
 River and coastal embankments, despite
many criticisms, are sine qua non to protect
lives, assets in floodplains
 No possibility of moving setback distance
further inland to accommodate water in the
channel
 To accommodate increased water volume in
rivers, embankment heights need to be
raised up to 1.5 m, including coastal
embankments (to prevent surge)
Embankments cont
 BD has more than 8,000 km of embankments,
many in bad shape due to lack of
maintenance (and encroachment)
 Floodplains will not be sustainable if
embankments are not sustainable
 Hence, prime concern is monitoring and
management of embankments, including
installation and operation of more sluice
gates to drain country-side water from
increased rainfall
Behavioral modification of rivers
 Channel improvement: (more rigorously)
(a) Dredging in prime sections including
around infrastructures & settlements
(b) River channel straightening thru’ loop
cutting, bypass, local structural control
(c) Groynes and spurs on river banks to
deflect floodwater and minimize bank
erosion
The purpose is to enhance river’s
conveyance capacity, and control its flow in
a planned manner
Flood preparedness
 Flood forecasting and warning is the most costeffective tool for minimizing losses from floods
 South Asian monsoon changes will affect flooding in
BD
 Hence, flood forecasting needs to be strengthened
 More upstream data should come from India, Nepal
as well as China
 Regional information exchange among GBM
countries on flood management measures
Climate-smart cropping
 Objective: to attain sustainability in floodplains thru’
addressing climate change challenge
 Crop diversification: to adapt to ecological changes
and prevent total crop failure from floods, drought &
unseasonable rainfall
 Expansion of hybrid rice cultivation to take
advantage of shorter growing period and high
productivity
 Climate resilient rice crop innovation (new species):
salt tolerant (for coastal region); submergence
tolerant (for flood prone central BD); and drought
tolerant (for drought prone northwestern BD)
Coastal floodplains
 Problems ahead: sea level rise in the Bay; salt water
ingress in soil, surface and ground water; more
intense cyclones and stronger surge; coastal
erosion = then, what to do for the coastal plain?
 Raising polder and embankment heights to prevent
sea water from entering inland farms & settlements
 Expansion of coastal afforestation and ‘green belt’
all along the coastline
 Introduction of salt resistant/tolerant rice and other
crops to offset increased soil and water salinity
continued
 Promotion of alternate livelihoods: brackish water
fisheries in lands unfit for crop agriculture;
expansion of shrimp farming (with effective
environmental safeguards)
 Cross dams between chars/mudflats to prevent
coastal & riverine erosion, and accelerate accretion
(for land reclamation)
 Sea wall or dykes to protect coastal ports, towns, &
other infrastructure (true it is expensive, but
selectively needed as essential option)
Summing up
 Floodplain is created by natural forces in river
basins, yet, another natural force: ‘climate change’
(caused by human actions) is threatening its
sustainability. ‘Do nothing’ is no more an option
 Actions to attain floodplain sustainability must be
proactive, with active participation of floodplain
users and managers: with both structural and nonstructural options should be explored and used
 Vision: Synergy between planned and autonomous
adaptation by floodplain managers (including
planners & administrators) and floodplain users or
inhabitants
Thank you all
for your attention