WATER INFORMATICS SCIENCE & ENGINEERINGEPSRC CENTRE FOR DOCTORAL TRAINING

www.wisecdt.org

Advanced hydraulic modelling for flood risk analysis Ioanna Stamataki, University of Bath

Supervisors: Dr. Jun Zang and Dr. Thomas Kjeldsen

Scientific Context One expected consequence of climate change is an increase in the frequency and magnitude of flooding, with approximately 21 million people globally threatened by it each year and expected to rise to 54 million by 2030. In line with these predictions, the European Commission is expecting the annual associated European damage costs to rise from €4.6 billion in 2012 to €23.5 billion by 2050.

Objectives •  Develop a verified and efficient 2D hydraulic model being able to accurately

predict flood inundation extents in extreme events.

•  Provide a 2D model that can be compared with existing industry models to assess their predictive ability.

Initial Model Validations •  Surface profiles for shock wave interaction with structures of different geometries:

•  Dam break at different time steps:

Acknowledgments I would like to thank the WISE EPSRC grant - EP/L016214/1.

Geophysical events (Earthquake, tsunami, volcanic activity)

Meteorological events (Tropical storm, extratropical storm, convective storm, local storm)

Hydrological events (Flood, mass movement)

Loss events

Climatological events (Extreme temperature, drought, wildfire)

Selection of catastrophes Overall losses ≥ US$ 1,500m

NatCatSERVICE

Loss events worldwide 2014 Geographical overview

© 2015 Münchener Rückversicherungs-Gesellschaft, Geo Risks Research, NatCatSERVICE – As at January 2015

Drought Brazil, 2014

Winter damage Japan, 7–16 Feb

Winter damage USA, Canada, 5–8 Jan

Drought USA, 2014

Earthquake China, 3 Aug

Floods India, Pakistan, 3–15 Sep

Floods United Kingdom, Dec 2013–Feb 2014

Severe storms France, Belgium, Germany, 7–10 Jun

Flash floods USA,11–13 Aug

Cyclone Hudhud India, 11–13 Oct

Severe storms USA, 18–23 May

Severe storms USA, 2–4 Apr

Severe storms USA, 27 Apr–1 May

Severe storms USA, 3–5 Jun

Typhoon Rammasun China, Philippines, Vietnam, 11–22 Jul

Source: Munich Re, NatCatSERVICE, 2015

Hurricane Odile Mexico, 11–17 Sep

980 Loss events

Typhoon Kalmaegi China, Philippines, Vietnam, 12–20 Sep

Floods Bosnia and Herzegovina, Serbia, Croatia, Romania, 13–30 May

Conclusion & Future Work The future work over the next few months will include the introduction of the wetting and drying component within the existing model. This will be then verified against literature and physical experiments. The objectives of the physical experiments will be to model the sharp flood wave front, validate the numerical model with large magnitude event data and provide high quality flash flood data to the research community in large scale testing.

Flash Flood Modelling: •  Flash flood characteristics very challenging

-  limited spatial and temporal scales •  Current 1D & 2D models are challenged due to:

- numerical instabilities - computational time -  the moving wet-dry interface -  the sharp flood wave front - data limitations

Need for Advanced Models: •  Ideally:

- calibration against different magnitudes - prediction of large magnitude events

Methodology 1.  Further development of non-linear shallow water equations existing model

−  Introduction of wet/dry boundary treatment, −  Incorporation of rainfall data −  Introduction of pre- and post- processing software Existing Model Advantages:

2.  Laboratory experiment to replicate flash flood conditions (possible HYDRALAB collaboration & dissertation student)

3.  Model validation 4.  Benchmarking of new model against test cases 5.  Field data from case studies (hydro-meteorological, LIDAR & OS Master Map) 6.  Model outputs compared with existing industry models

•  Dynamically adaptive grid •  High resolution mesh •  Godunov- type solver •  Cut cell technique •  Quadtree grid •  Boundary fitting scheme

•  Robust simulations •  Adjustable to local topography •  Computationally efficient, •  Shock capturing •  No numerical instabilities •  Prediction of discontinuous flows

Figures: Adaptive quadtree grids describing a circle without [a] and with [b] cut cells. [c] Technique for updating flow information on cut cells

[a] [b] [c]

Figures: Flash flood laboratory experiment, photo and plan set-up respectively

References Borga, M., Anagnostou, E.N., Blöschl, G. & Creutin, J.D., 2011. Flash flood forecasting, warning and risk management: the HYDRATE project. Environmental Science & Policy, 14, pp.834-44. Cooper R. & Bentley P.. 2013. Dailymail. [ONLINE] Available at: http://www.dailymail.co.uk/news/article-2381130/Flash-floods-strike-Yorkshire-village-heatwave-set-return-temperatures-32C.html. [Accessed 15 June 15]. Horritt, M.S. & Bates, P.D., 2002. Evaluation of 1D and 2D numerical models for predicting river flood inundation. Journal of Hydrology, 268, pp.87-99. Liang, & Borthwick, A.G.L., 2009. Adaptive quadtree simulation of shallow flows with wet–dry fronts over complex topography. Computers & Fluids, 38, pp.221–34. Liang, Q., Zang, J., Borthwick, A.G.L. & Taylor, P.H., 2007. Shallow flow simulation on dynamically adaptive cut cell quadtree grids. International Journal for Numerical Methods in Fluids, 53, pp.1777-99. Munich RE, 2015. Loss events worldwide Jan-June 2015 [Online] Geo Risk Research, NatCatSERVICE Available at: https://www.munichre.com/site/wrap/get/documents_E-960403530/mram/assetpool.mr_america/PDFs/5_Press_News/Press/2015_World_map_losses.pdf [Accessed 29 January 2016]. Quevauviller, P.P., 2015. Hydrometeorological Hazards: Interfacing Science and Policy. 1st ed. John Wiley & Sons. Robson D.. 2008. Visiting an edge of a continent. [ONLINE] Available at: http://independentstitch.typepad.com/the_independent_stitch/2008/08/living-on-an-ed.html. [Accessed 06 June 15]. Sene, K., 2013. Flash Floods Forecasting and Warning. 1st ed. New York: Springer. Sharma N.C.. 2014. Government ignored its own disaster report despite warning that J&K is 'highly susceptible' to flash floods. [ONLINE] Available at: http://www.dailymail.co.uk/indiahome/indianews/article-2752676/Government-ignored-disaster-report-despite-warning-J-K-highly-susceptible-flash-floods.html. [Accessed 06 June 15]. Soares-Frazão, S. and Zech, Y. (2008). Dam-break flow through an idealised city. Journal of Hydraulic Research, 46(5), pp.648-658. Wang, J.P. & Liang, Q., 2011. Testing a new adaptive grid-based shallow flow model for different types of flood simulations. Journal of Flood Risk Management, 4, pp.96-103. Xia, J., Falconer, R.A., Lin, B. & Tan, G., 2011. Modelling flash flood risk in urban areas. Water Management, 164(WM6), pp.267-82.

Figure: Depth distribution during peak discharge

Figure: Munich RE: 2015 natural hazard events

Figure: 2013 flash flood in Yorkshire

Figure: 2011 Floods in Srinagar, India