Exposure to Severe Weather Events: A review of recent experience in the Western Cape Disaster Mitigation for Sustainable Livelihoods Programme University of Cape Town September, 2009 Ailsa Holloway, Gillian Fortune,

Presentation Focus Knysna 2007 Southern Cape 2006 Port Shepstone 2008 Role of ex post analysis in managing climate risk Overview of recent severe weather in Western Cape Reflection on severe weather & consequences for flood risk management. Unpacking ‘ causal chain’’ between ‘development’ and severe weather impacts

Managing Risk – Role of Ex Post Analysis Risk is a probalistic concept – about a future negative outcome (it has yet to happen)Risk is a probalistic concept – about a future negative outcome (it has yet to happen) ‘Ex post’ disaster event research analyses actual events that have happened.‘Ex post’ disaster event research analyses actual events that have happened.

It provides useful insights about: –What/who resists and what fails in a severe weather event. The ‘what’, the ‘where’ and the ‘when’ and the ‘who’ –How much this costs –The causal chain that leads to the loss (ie the mix of risk factors) the –The causal chain that leads to the loss (ie the mix of risk factors) the ‘why’ and the ‘how’ –Ex post research studies actual disaster events to guide risk averse development

June 241 mm 228mm 218mm 324mm Nov 150 mm 206 mm Severe Weather Events for 2003, 2004, 2005, 2006, 2007 and July Nov 93 mm 93 mm 150 mm

Date Area most affected Loss (R. Mil)* Mar 2003 Eden212.4 Dec 2004 Eden > 60.0 Apr 2005 Overberg5.0 Aug 2006 Eden & Overberg Jun 2007 West Coast Nov 2007 Eden & Overberg 1.2 bn Jul 2008 West Coast 74.1 Nov 2008 Overberg & Cape Winelands Total Four districts R 3 bn in 6 yrs Severe weather events - costly for W. Cape * Not adjusted for inflation

Focus on Cut-off Lows Affecting Eden ie Prov. Depts and Municipal Impacts ie Prov. Depts and Municipal Impacts 2003Mar2006Aug2007Nov2008NovTotal (R. m) ProvDepts bn Municips in Eden Severe weather losses

Prov. Dept Total Housing Agriculture Cape Nat Education Prov Roads Public Wks Social Dev Total bn Provincial losses are substantial (2003, 2006 & 2007 weather events total R 1.2 bn) 2007 losses up by more than five times March 2003

A Review of Ten Damage-Bearing Severe Weather Events Since 2003 Cape Town August 2004 and 2008 W. CoastJune 2007, July 2008 Winelands/ March 2003, April 2005, Overberg November 2008 EdenDecember 2004, August 2006 November 2007

Cape Town – August 2004 and 2008 A little history… Image from 23 June, mm fell in one hour

100 years later… 5-9 August 2004 (2 large cold fronts) Resulted in flooding in Maitland, Woodstock, Pinelands, Athlone, Bonteheuvel, Nyanga, Guguletu and Somerset West (Mainly Salt Water Catchment)Resulted in flooding in Maitland, Woodstock, Pinelands, Athlone, Bonteheuvel, Nyanga, Guguletu and Somerset West (Mainly Salt Water Catchment) Peak rainfall intensities over 3 hr durations exceeded 100 year storm Athlone (67mm) & Pinelands (62 mm)Peak rainfall intensities over 3 hr durations exceeded 100 year storm Athlone (67mm) & Pinelands (62 mm) Source: CoCT in 2004 Storm Report on

Cape Town Superstorm, August 2008 Storm surge > 5 m and wave heights > 7 metres; Images 24 hour rainfall, 30 August 2008 (46% August monthly rainfall – 24 hrs) Source: Thea Beckman, UCT 100mm

West Coast June June (Cut-off low), June (Frontal system) First event … rainfall over Bergriver Municipality > 130 mm (but total rain mm); Swartland (120mm) Saldhana Bay (110 mm)First event … rainfall over Bergriver Municipality > 130 mm (but total rain mm); Swartland (120mm) Saldhana Bay (110 mm) Second event … Rainfall over Witzenberg Municipality > 50 mmSecond event … Rainfall over Witzenberg Municipality > 50 mm Combined totals for June 2007 … 200 mm greater than mean historical averageCombined totals for June 2007 … 200 mm greater than mean historical average Roode Els Berg 289 mm Assegaibos 328 mm Ceres 394 mm Hawequas 219 mm Jonkershoek 198 mm

West Coast and Western Winelands 4 – 9 July 2008 (Cut off low) Most striking feature – long duration of heavy precipitation.Most striking feature – long duration of heavy precipitation. Wettest July in recent history for Ceres, Roode Els BergWettest July in recent history for Ceres, Roode Els Berg July 2008 totals were 300% (Roode Els Berg), 145% (Assegaibos) and 200% (Ceres) of July mean rainfallJuly 2008 totals were 300% (Roode Els Berg), 145% (Assegaibos) and 200% (Ceres) of July mean rainfall

2003 and 2005 Winelands and Overberg Cut-off Lows March 2003 ‘Montagu floods’22-25 March 2003 ‘Montagu floods’ 241 mm in Montagu, (Kingna River – mainly responsible for flooding) (Kingna River – mainly responsible for flooding) 160 mm in Swellendam April 2005, ‘Bredasdorp flood’ 228 mm rain10-12 April 2005, ‘Bredasdorp flood’ 228 mm rain

11-13 November 2008 Cut off Low – Overberg and Winelands Korinte-vetdam 281 mm Hawequas Forest 250 mm Meterologically, less significant than 2007 cut-off low during the same month. However, still significant losses – and research now ongoing

Eden - December 2004, Jul/August 2006, November 2007 Cut-off lows 21 – 23 December 2004 (Heidelberg 168 mm, Knysna 219 mm) Flood line inside a house on the Duiwenhoks River Heidelberg Municipal Chalets 22 Dec, 2004

Jul/August 2006 George Rainfall 31 Jul – 4 Aug mm PLUS PLUS 21 – 24 Aug mm Total 446 mm

2006 Cut-off low profiled exposures generated by non-perennial floodways that flash-flood in a severe weather event Source: Xavier Middleton

1957 to to 2004 It also indicated the role of increasing urbanisation in George Municipality from 1957 to 2004… Increased by hectares from 1957 to 1985 Increased by 7,488.4 hectares from 1985 to 2004 Source: Xavier Middleton

21-22 November 2007 Cut-off Low Wolwedansdam 316 mm George 333 mm This 3-day event created new rainfall records for areas it affected: Contributed over 70% to highest November total rainfall in the last 30 years Assegaibos – 500% and George 530%, respectively of the November mean.

Institutional risk factors (ie under- investment in municipal maintenance) S Planned Per Capita Expenditure Municip.Pop. Gross Econ Loss [Million ZAR] Maintenance & Repair [per cap] Econ. Loss [ per cap] Bitou George Knysna Mossel Bay Oudtshoorn Total

Investments in municipal maintenance are protective and reduce losses

To conclude: Severe weather is a reality for us in the Western Cape – no region can be complacent.Severe weather is a reality for us in the Western Cape – no region can be complacent. There has been impressive improvement in managing severe weather since 2003 … especially in mobilising following warnings.There has been impressive improvement in managing severe weather since 2003 … especially in mobilising following warnings. However… still a long way to reducing climate risk developmentally..However… still a long way to reducing climate risk developmentally..