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Risks in the built environment in a changing world
Bob ScholesCSIR Natural Resources and Environment
5Feb 2013 SAIA workshop
Question 1: What aspects of the built environment present risks that could be collaboratively addressed?
• Coastal Flooding due to sea level rise and storms• Inland flooding due to increased storm intensity• Fires, especially megafires due to climate change• Drought, particularly in western southern Africa
Sea level rise
Cazenave & Llovel 2010 Contemporary Sea Level Rise. Ann Rev Marine Sci 2, 145-173
Rahmstorf 2007 Science 316:368
IPCC AR4
Tide gaugesChurch et al 2004
Satellites
Historicalsources
Sea level rise, plus changes in storm intensity, combined with tidal dynamics and increased coastal development.
CSIR has developed a wave climate model for the entire coastline. Detailed analyses for specific locations require high-resolution bathymetry and altimetry
Sea level rise will effect even South Africa
Predicted SA runup elevations on exposed coastsSpring tide (MHWS) & 1-in10yr wave height (Hs)
5
6
7
8
9
Location (East to West)
Ru
nu
p e
lev
ati
on
(m
MS
L)
2% runup mild slope 2% runup steep slope2% runup steep slope +10% wave height 2% runup steep slope +0.5m SLR2% runup steep slope +10% wave +0.5m SLR
© CSIR 2007 www.csir.co.za
A general increase in the frequency of extreme
rainfall events, especially the highveld
Projected change in
extreme rain events over South Africa
(>20 mm in 24 hours over an area of 50 km x 50 km)
Slide: Francois Engelbrecht, CSIR
Question 2: Practical steps, by whom… coastal flooding
Body Topic Action
Surveyor General, SA Navy, private firms
Near coast high resolution altimetry and bathymetry
Survey areas of infrastructure
CSIR Surge mapping Apply models to map impact areas
Local authorities Building permits Do not give permits in at risk areas
Insurance industry Insurance premiums Structure premiums to reflect changing risk
Coastal management Coastal protection Dune, beach and estuary management
Question 2: Practical steps … inland floodingBody Topic Action
CSIR Downscaled climate Models with 8 km resolution for 21st century
Hydrologists: universitis and consultancies
Flood return statistics New tables and maps for 20 and 100 yr floods
DWA Catchment management Restoration, flood control structures, management of flows
National Disaster Management, DWA and SAWS
Real-time warning Models and observaion system with alerts
Planning authorities Reduction in exposure Control development in flood zone
Question 2 cont: Practical steps…fireBody Topic Action
CSIR Advanced Fire Information System
Realtime warning
SAWS Fire danger index 24 and 48 hour forecasts
Working on Fire Fire avoidance Fuel reduction, firebreaks
National Disaster Management
Rapid intervention Response teams for megafires
Planning authorities Reduction in exposure Control buiding in fire-prone areas
Fire Protection associations Avoidance and response Firebreaks, local response teams
Question 2 cont: Practical steps…drought
Body Topic Action
CSIR, UCT-CESAG Downscaled aridity projections
Drought probability maps for future climates
ARC, SANSA, SAWS Early warning, affected area verification
Greenness and wetness anomalies
DAFF, Provincial authorities, Farmers organisations
Non-financial insurance avoids damage rather than compensating for it
Forage and livestock bankingRapid offtake schemes
Insurance industry Financial insurance for farmers taking appropriate adaptation steps
Re-assess risks as they change through the century
End of brief presentation
Human vs Natural Causes
Evidence of a changing world
2071-2100 vs 1961-1990
Southern Africa is projected to warm at a
higher rate than the global average
CCAM ensemble-average projected change in the Annual frequency of very hot days
(>35C, 2071-2100 vs 1961-1990)
..but rainfall futures remain
uncertain for our region
Ensemble average
AgricultureClimate change effects are negative overall
Blignaut et alDube & Scholes 2011
Scholes livestock: substantial decrease in production
Rising temperatures arethe key driver, even once rain and CO2 are factored in
But,1. Large yield gap in Africa
(5x)2. Substantial potential for
crop area expansion in in sub-humid Africa (2x)