CGE Training materials - VULNERABILITY AND ADAPTATION AssessmentCHAPTER 5 Coastal Resources
Expectation from the Training Material • Having read this presentation, in conjunction with the related handbook, the reader should: • Be able to identify the drivers and potential impacts of climate change on coastal zones • Have an overview of the methodological approaches, tools and data available to assess the impact of climate change on coastal zones • Be able to identify appropriate adaptation measures.
Outline • Overview of drivers and potential impacts of climate change on coastal zone; • Methods, tools and data requirements on coastal zone integrated assessment methods and models, including an overview of ENSO and sea level data; • Adaptation planning in the coastal sector
Climate Change and Coastal Resources • Coastal resources will be affected by a number of consequences of climate change, including: • Higher sea levels • Higher sea temperatures, sea-surface temperature, • El Niño/La Niña-Southern Oscillation (ENSO) events/climate cycle • Changes in precipitation patterns and coastal run-off • Changes in storm tracks, frequencies, and intensities, and • Other factors such as wave climate, storminess, and land subsidence.
Climate Change: Global context 1900-2000: Global mean surface air temp increased by 0.6 0C Projected increase (1990-2100): 1.4 – 5.80C (Based on greenhouse gas emission) 2030: + 0.7 in monsoon,+ 1.3 in winter 2050: + 1.1, + 1.8 in 2050. (Source: IPCC report)
Current Global Predictions of Sea Level Rise • Conclusions about future SLR in the IPCC’s Third Assessment Report (TAR, 2001) and Fourth Assessment Report (AR4, 2007) were broadly similar. • The IPCC AR4 projections estimated global sea-level rise of up to 79 cm by 2100, noting the risk that the contribution of ice sheets to sea level this century could be higher.
Post AR4 • Research since AR4 has suggested that dynamic processes, particularly the loss of shelf ice that buttresses outlet glaciers, can lead to more rapid loss of ice than melting of the top surface ice alone. • There is a growing consensus in the science community that SLR at the upper end of the IPCC estimates is plausible by the end of this century, and that a rise of more than 1.0 metre and as high as 1.5 metres cannot be ruled out.
Post AR4 (Source: Church et al., 2008)
Projected Global Average Surface and Sea Level Rise at the end of 21st Century Notes: aThese estimates are assessed from a hierarchy of models that encompass a simple climate model, several Earth System Models of Intermediate Complexity, and a large number of Atmosphere-Ocean General Circulation Models (AOGCMs). bYear 2000 constant composition is derived from AOGCMs only. (Source: IPCC, 2007a)
IPCC AR4 is missing the rapid ice flow changes…. “…an improved estimate of the range of SLR to 2100 including increased ice dynamics lies between 0.8 and 2.0 m.” Recent findings ~1 m Considering the dynamic effect of ice-melt contribution to global sea level rise, Vermeer and Rahmstorf (2009) estimated that by 2100 the sea level rise would be approximately three times as much as projected (excluding rapid ice flow dynamics) by the IPCC-AR4 assessment. Even for the lowest emission scenario (B1), sea level rise is then likely to be about 1 m and may even come closer to 2 m. Also see http://www.msnbc.msn.com/id/42878011/ns/us_news-environment
El Niño/ La Niña -Southern Oscillation (ENSO)-Another Major Driver of Climate Change Develops in JulAugSept, strengthen through OctNovDec, and weakens in JanFebMar (Warm SST) lowP • El Niño - major warming of the equatorial waters in the Pacific Ocean • The anomaly of the SST in the tropical Pacific increases (+0.5 to +1.5 deg. C in NINO 3.4 area) from its long-term average; • A high pressure region is formed in the western Pacific and low-pressure region is formed in the eastern Pacific —this produces a negative ENSO index (SOI negative). • La Niña—major cooling of the equatorial waters in the Pacific Ocean • The anomaly of the SST in the tropical Pacific decreases (-0.5 to -1.5 deg. C in NINO 3.4 area) from its long-term average; • A high pressure region is formed in the eastern Pacific and low-pressure region is formed in the western Pacific—this produces a positive ENSO index (SOI positive). H(Cold SST) low (Source: IRI Web Portal)
SA B H A G M NWP NINO 3.4 Nino 4 Nino 3 SP AS E W
El Niño/ La Niña Years (1950-2012) The number of El Niño/ La Niña years has considerably increased in the recent years. Scientists argue that this is the result of climate variability and change (instability) and… This trend is likely to continue in future as we are in a stage of changing climate… So, more frequent extreme events are likely in the future. 12 *2008-09 13 *2009-11
Impacts of ENSO: Venezuela • Venezuela is in the midst of a genuine power and water crisis. There may not be a clear cut answer to this question “What is causing Venezuela's energy crisis”, and different people provide different interpretations. • Among others, pointing the finger at weather changes, President Chávez said “It's El Niño,” partly to be blamed for this recent crunch; • The El Niño is blamed for a lack of rainfall and the cause of water shortages, which in turn have starved Venezuela's hydroelectric dams which provide approximately three quarters of the nation's electricity.
Land Subsidence Subsidence on the coast of Turkey following an earthquake in 1999
Non-Climate Drivers • Port/harbour construction • Coastal protection works • Upstream damming for freshwater supply • Hydroelectric power • Deforestation • Coastal subsidence due to ground water abstraction — particularly significant in delta region • Socio-economic scenario changes in coastal regions including urbanization • Geological natural hazards — earthquake.
Uncertainty in Local Predictions • Relative sea level rise: global and regional components plus land movement: • Land uplift will counter any global sea level rise • Land subsidence will exacerbate any global sea level rise • Other dynamic oceanic and climatic effects cause regional differences (oceanic circulation, wind and pressure, and ocean-water density differences add additional components).
Science Summary • Under a high-emissions scenario, an SLR of up to a metre or more by the end of the century is plausible. • Changes in the frequency and magnitude of extreme sea level events, such as storm surges combined with higher mean sea level, will lead to escalating risks of coastal inundation. Under the highest SLR scenario, by mid-century, inundations that previously occurred once every hundred years could happen several times a year. • SLR will not stabilize by 2100. Regardless of reductions in greenhouse gas emissions, sea level will continue to rise for centuries; an eventual rise of several metres is possible.
Impacts of Climate Change: Antigua and Barbuda • Damage to critical habitats (beaches, mangroves, sea grass beds, coral reefs) • Loss of wetlands, lands due to sea level change • Increased coral bleaching as a result of a 2°C increase in SST by 2099 • Destruction to coastal infrastructure, loss of lives and property • Changes in coastal pollutants will occur with changes in precipitation and run-off • General economic losses to the country. Source: http://unfccc.int/resource/docs/natc/antnc2.pdf Also see: http://unfccc.int/national_reports/non-annex_i_natcom/items/2979.php
Tianjin Dhaka Seoul Osaka Istanbul Tokyo New York Shanghai Los Angeles Manila Bangkok Lagos Mumbai Lima Karachi Madras Jakarta Rio de Janeiro Buenos Aires Calcutta Coastal Megacities (>8 million people)
Elevation and Population Density Maps for Southeast Asia Indo-China Peninsula
Sea-Level Rise: Summary • Research indicates: • Doubled melting rate of Greenland ice sheet • Net melting of the Antarctic ice sheet • Global rise approaching 3.0 mm/yr, twice the rate last century, • Continued heating of atmosphere – heating of water column, • More than 1 m rise is now expected during this century. • 30C temperature rise suggests 3-6 m SLR in a century. • There are still major uncertainties in sea-level science, but these latest results are significant in that: • They do not point in the direction of smaller rates of rise, • They are consistent with the worse case of long-standing predictions, • Counter arguments grow fewer and fewer…
Level of Assessment: Screening Assessment • This is a rapid assessment to highlight possible impacts of a sea level rise scenario and identify information/data gaps. • Qualitative or semi-quantitative. • Steps • Collation of existing coastal data • Assessment of the possible impacts of a 1-m sea level rise • Implications of future development • Possible responses to the problems caused by SLR
Step 1: Collation of Existing Data Topographic surveys Aerial/remote sensing images – topography/ land cover Coastal geomorphology classification Evidence of subsidence Long-term relative SLR Magnitude and damage caused by flooding Coastal erosion Population density Activities located on the coast (cities, ports, resort areas and tourist beaches, industrial and agricultural areas).
Step 2: Assessment of Possible Impacts of 1m Sea Level Rise • Four impacts are considered: • Increased storm flooding • Beach/bluff erosion • Wetland and mangrove inundation and loss • Salt water intrusion
(i) Increased Storm Flooding • Describe what is located in flood-prone areas. • Describe historical floods, including location, magnitude and damage, the response of the local people, and the response of government. • How have policies toward flooding evolved?
(ii) Beach/bluff Erosion • Describe what is located within 300 m of the ocean coast. • Describe beach types. • Describe the various livelihoods of the people living in coastal areas such as commercial fishers, international-based coastal tourism, or subsistence lifestyles. • Describe any existing problems of beach erosion including quantitative data. These areas will experience more rapid erosion given accelerated sea level rise. • For important beach areas, conduct a Bruun rule analysis (Nicholls, 1998) to assess the potential for shoreline recession given a 1-m rise in sea level. • What existing coastal infrastructure might be impacted by such recession?
(iii) Wetland and Mangrove Inundation • Describe the wetland areas, including human activities and resources that depend on the wetlands. For instance, are mangroves being cut and used, or do fisheries depend on wetlands? • Have wetlands or mangroves been reclaimed for other uses, and is this likely to continue? • Are these wetlands viewed as a valuable resource for coastal fisheries and hunting or merely thought of as wastelands?
(iv) Salt Water Intrusion • Is there any existing problem with water supply for drinking purposes? • Does it seem likely that salinization due to sea level rise will be a problem for surface and/or subsurface water?
Step 3: Implications of Future Developments • New and existing river dams and impacts on downstream deltas • New coastal settlements • Expansion of coastal tourism • Possibility of transmigration
Step 4: Responses to the Sea Level Rise Impacts • Protect (i.e. hard and soft defences, seawalls, beach nourishment). • Planned retreat (i.e. setback of defenses) • Accommodate (i.e. raise buildings above flood levels)
Bruun Rule R = shoreline recession due to a sea-level rise S h* = depth at the offshore boundary B = appropriate land elevation L = active profile width between boundaries G = inverse of the overfill ratio R = G(L/H)S; where H=B + h*
Beach Profile in Equilibrium with Sea Level Y X Eroded profile Accreted profile Depth of closure Y/X = 50 to 200….say, 100 1 m sea level rise = 100 m (~400 ft) shoreline recession
Limitations of the Bruun Rule • Only describes one of the processes affecting sandy beaches • Indirect effect of mean SLR: • Estuaries and inlets maintain equilibrium • Act as major sinks • Sand eroded from adjacent coast • Increased erosion rates. • Response time – best applied over long timescales.
Coastal Vulnerability Assessment • Vulnerability assessment (1-2 years): • Erosion • Flooding • Coastal wetland/ecosystem loss. • The aim of screening and vulnerability assessment is to scale prioritization of concern and to target future studies, rather than to provide detailed predictions.