Towards an integrated assessment of coastal flood risk in southern China.

Transcription

1 Towards an integrated assessment of coastal flood risk in southern China. ADAM D. SWITZER EARTH OBSERVATORY OF SINGAPORE ASIAN SCHOOL OF THE ENVIRONMENT NANYANG TECHNOLOGICAL UNIVERSITY test.candrholdings.com/big smog/features/60965/the pearl river delta megacity.html 1

2 The triple threat Sea level, storms and tsunamis M QE jpg test.candrholdings.com/media/138/typhoon 3 slide.jpg Sea level and coastal flooding New York City, USA 2

3 Contributions to sea level rise? Projections from process based models of (a) GMSL rise relative to : (IPCC) Mass redistribution from ice loss creates a fingerprint New York: 1 m SLR equivalent ice loss from Greenland=~0.6 m SLR 1 m SLR from Antarctica = ~1.2m SLR What if they both melt? Hong Kong, Singapore, Bangkok, Jakarta 1 m SLR equivalent ice loss from Greenland=~ m SLR 1 m SLR from Antarctica = ~ m SLR What happens when you take a block of ice and spread it over the ocean. 1. Reduced gravitational attraction. 2. Change moment of inertia/rotation axis 3. Elastic rebound 4. Viscous flow of displaced mantle. 1,2,3 happen for our purposes, immediately; 4 takes 10s of thousands of years. Greenland Antarctica 3

4 Sea level extremes make sea level rise important Integrating sea level extreme analysis in southern China. Questions for today 1. Will rising sea level increase tsunami induced flooding hazard: a case study in Macau 2. How will storm surge hazard evolve under changing climate in the southern China. 4

5 Macau has one of the highest population densities in the world and very concentrated major infrastructure. Population density: 21,236 pop./km 2 Hong Kong Zhuhai Macau bridge Deep water harbor Casinos! 2/3 of Macau s current land is reclaimed land B Taipa Cotai The land reclamation history modified from Jiang et al. [2011] 4m bare ground topographic data provided by NTTDATA 5

6 Quantify the effect of SLR on tsunami hazard Probabilistic tsunami inundation map Current sea level vs. 0.5 m sea level rise vs. 1.0 m sea level rise Baseline By 2060 By 2100 What happens as sea level rises? Tsunami modelling China Mw=8.6 Taiwan Guangdong Macau HK Philippines South China Sea PTHA Fault models generated by a hybrid kinematic squared source model proposed by Gallovič and Brokešová [2007] Li et al., J. Geophys. Res.,

7 Tsunami inundation simulations for synthetic EQs with Mw >= 8 Earthquake numbers in 100,000 years Use high-resolution bathymetric and topographic data Nautical charts 4 m resolution DSM 36 nautical charts 4 m resolution DSM / 1-arc SRTM data GEBCO data 7

8 Why choose Macau to demonstrate the effect of SLR? 500-year 1000-year South China Sea Li et al., J. Geophys. Res., 2016 Macau tsunami modelling China Mw=8.6 Taiwan Philippines Fault models generated by a hybrid kinematic squared source model proposed by Gallovič and Brokešová [2007] Stochastic fault models for 110 earthquakes of Mw 8.6 Synthetic Wave Gauges (SWG) are set along 10-m isobaths and shallower area near Macau 8

9 Macau tsunami modelling 2 3 m difference in water depth could be expected in 110 Mw8.6 scenarios Stochastic models provide a wide range of possible tsunami wave heights Macau tsunami hazard Today Mw = 9.0 Return period: 2500 years Mw = 8.8 Return period: 1466 years Mw = 8.6 Return period: 925 years Adam D. Switzer 9

10 Macau tsunami hazard Today vs 0.5m SLR Add 0.5m of sea level rise Macau tsunami hazard Today vs 1m SLR Add a 1m of sea level rise 10

11 0.5 m and 1m SLR would dramatically increase the frequency of tsunami induced flooding incidences of a factor of ~2 and Integrating sea level extreme analysis in southern China. Today Macau is relatively tsunami safe A modest increase in sea level of tsunami risk in Macau. 1m increases the risk by times 11

12 Integrating sea level extreme analysis in southern China. Questions for today 1. Will rising sea level increase tsunami induced flooding hazard: a case study in Macau 2. How will storm surge hazard evolve under changing climate in the southern China. Multi layer unstructured mesh for SCS with the focus on Pearl River Delta Pearl River Delta 12

13 Using 3D ocean model FVCOM to simulate the surge events: e.g. Hagupit (2008) Generate wind field using parametric models, e.g, Holland model A closer look Using 3D ocean model FVCOM to reproduce surge events in this region: validate against tide gauge 13

14 Synthetic typhoons are generated under different climate conditions based on 8 selected downscaled regional climate models With our new synthetic datasets we can - 1. produce worst case scenarios and investigate sensitivity to translation speed, tidal cycle, Example for New York by Lin et al., Nat. Clim

15 With our new synthetic datasets we can - 2. Examine the differences between climate model outputs and cyclone climatology The black is present climate, the blue is for the IPCC A1B climate and the red is for the IPCC A1B climate with R o increased by 10% and R m increased by 21%. Shading = 90% confidence interval. Example for New York by Lin et al., Nat. Clim Integrating sea level extreme analysis in southern China. Typhoon risk in PRD region will likely increase significantly by 2050 This is a result of rising baseline sea level, changes in cyclone climatology in the western Pacific The uncertainties are large and underscore the importance of further studies on storm climatology in the region 15