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A key modulator of people's threat assessment is the degree of trust they have in the ... Means of increasing compliance with evacuation orders are described, including .... orders and evacuation compliance, Murrumbidgee towns, March 2012 flood .... response rate was the role of Hay's mayor in publicly questioning the ...
GOOD, BAD AND UGLY: EXPLORING EVACUATION COMPLIANCE, MURRUMBIDGEE REGION FLOODING, MARCH 2012 S Yeo1,3, A Gissing2,3, K Haynes3, C Keys2, S Gray4, Z Richards4 Flood Focus Consulting Pty Ltd, Sydney, NSW Risk Frontiers, Sydney, NSW 3 Macquarie University, Sydney, NSW 4 GRC Hydro Pty Ltd, Sydney, NSW 1 2

Abstract Previous floods in NSW have highlighted the difficulties of achieving compliance with evacuation orders. This paper draws on interviews with the emergency services and residents to explore evacuation behaviours for five levee-protected communities in the Murrumbidgee region of NSW during flooding in March 2012. High rates of compliance were observed at North Wagga Wagga, Wagga Wagga and Darlington Point, but low rates were observed at Hay and Urana. Key drivers of these behaviours appear to be the perceived credibility of the stated threat of flooding, and people’s assessment of their capacities to cope with any impacts should they not evacuate. A key modulator of people’s threat assessment is the degree of trust they have in the emergency services and the information they issue. The exclusion of local knowledge from the decision-making process, or public disagreement between state and local authorities erodes confidence in the evacuation order. Means of increasing compliance with evacuation orders are described, including improving flood intelligence, and engaging local communities as equal players in setting evacuation triggers.

Introduction Evacuation in advance of flooding is a key life-saving response for communities living and working on floodplains. It has particular importance for communities protected by levees, which may fail during floods larger than their design limit, rapidly inundating the protected area. The high loss of life (1,464)1 associated with the failure of New Orleans’ levees during flooding from Hurricane Katrina in 2005 is a reminder of the need for early evacuation, including of those who lack the means to self-evacuate. Whilst no one perished, the breaching of sandbags used to bolster Nyngan’s levee system in 1990, the failure to evacuate the town prior to the flood, and the subsequent mass rescue by boats and helicopters and the temporary relocation of the town’s 2,300 residents to Dubbo (DWR, 1990), is a compelling local reminder of the priority of early evacuation, and of the challenge of evacuating communities with ring levees where there are large distances to travel. In NSW, the State Emergency Service (SES) is vested with the authority to order evacuation of an emergency area (State Emergency Service Act 1989, Section 22(1)). Local flood plans (e.g. NSW SES, 2006; 2013; 2014) stipulate typical evacuation triggers, including:  likely flooding of homes or businesses;  failure or likely failure of essential energy and utility services; or  isolation of people unsuited to living in isolated circumstances. Good, bad and ugly: exploring evacuation compliance, Murrumbidgee region flooding, March 2012 2018 Floodplain Management Australia National Conference, Gold Coast

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Each of these three evacuation triggers is depicted in Figure 1 and is considered further below:  Flooding of homes or businesses. For levee-protected communities that receive formal height-time predictions, the SES normally triggers evacuations when the Bureau of Meteorology (BoM) issues a flood height prediction that exceeds the design height of the levee, if this is known and stipulated in the relevant local flood plan. The levee’s design height is usually lower than the actual crest level, which typically includes a freeboard to allow for uncertainties including in design flood estimation, wind/wave action, and erosion and settlement of earthen levees (Mark et al., 2010). Asset managers will also monitor a levee’s structural integrity and advise the SES of the threat of failure. Only if the SES has high confidence that a levee will not be overtopped or otherwise fail might non-evacuation of the protected area be considered tolerable.  Failure of essential services. Confidence that essential services will remain operational during the flood – or that appropriate contingencies can be put in place (e.g. boil water alerts) – is also considered a prerequisite for non-evacuation.  Isolation of vulnerable people. Residents of nursing homes or people with a range of other vulnerabilities (e.g. chronically ill, disabled) who require additional care may be evacuated or urged to evacuate in advance of a flood. Yet it is increasingly recognised that the process of evacuation may itself present a greater risk than remaining on site, with a meta-analysis of 10 studies finding an increase in mortality among nursing home residents of 10% for the month after evacuations (Willoughby et al., 2017).2 For this reason the SES does not treat evacuation decisions lightly. Although not favoured due to the known risks of isolation including the difficulty of servicing fire and medical emergencies, it appears that at least for the communities under consideration in this paper, the SES might not necessarily trigger broad evacuations if only isolation is anticipated, provided essential services can continue and contingency plans are in place in case of levee failure.

Figure 1: General evacuation triggers for levee-protected communities in NSW

Good, bad and ugly: exploring evacuation compliance, Murrumbidgee region flooding, March 2012 2018 Floodplain Management Australia National Conference, Gold Coast

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But successful evacuation requires that communities comply with instructions to evacuate. Previous floods in NSW have highlighted the difficulties of achieving such compliance (Pfister, 2002; Molino Stewart, 2009). Understanding why some communities fail to comply while others comply in timely fashion is important for improving responsiveness in future floods. Major flooding affected the Murrumbidgee River and nearby creek and river systems in southwest NSW in March 2012. The flooding was the highest since 1974 for many towns, and exceeded the previous record 1931 extent at Urana. Evacuation orders were issued for several towns and villages. The markedly different community responses to these orders present an opportunity to investigate evacuation behaviours. Five communities are considered in this paper: North Wagga Wagga, central Wagga Wagga, Darlington Point, Hay and Urana (see Figure 2). Recognising the difficulty of making decisions under the uncertainties that prevail during flood operations, the intention of this paper is not to apply the luxury of hindsight nor to cast judgment upon the management of flood operations. The aim is to better understand predictors of evacuation, and to put forward recommendations to enhance community responsiveness to evacuation orders for future flood events.

Context: evacuation behaviour drivers Figure 3 summarises factors influencing people’s evacuation behaviours, based on the evacuation literature and learnings from the Murrumbidgee region case studies. Evacuation behaviours are shaped by a tension between people’s assessment of the threat and inertia to stay. If the threat is considered credible, and is judged to present unacceptable risks, the drive to evacuate may overtake the inertia to stay. But if the likelihood of the threat actualising is considered low, or its impacts are considered manageable, the inertia to stay may win out. How people assess the threat draws on many potential sources including their own observations and previous experience, their networks of family, friends and neighbours, media and social media platforms, and official information providers including the local council and SES. As will be shown, the degree of trust in these authorities modulates how their communications are received. Some of the many reasons why people are naturally disinclined to evacuate are listed, including an inability to evacuate. Psychological predispositions undergird people’s thinking. But a heavy presence of the emergency services may short-circuit people’s risk assessments and promote evacuation. One reason why ordering communities to evacuate is often a fraught exercise (see Keys, 2015) is because quite different standards of risk acceptance are in play. The emergency services tend to be risk-averse because they are legislated to protect life and property. Community members appear to be more risk-accepting, possibly reflecting an optimism bias. They may innately think a levee is unlikely to overtop or fail, or that they could cope with anticipated flood depths if the worst were to occur. Only if they are confident that a levee will be overtopped or otherwise fail, and that the ensuing flood conditions will present unacceptable dangers, might they concede that evacuation is warranted. The concept of a levee’s design height, which might be one metre below the actual levee crest, is difficult to comprehend. Also, the intrinsic uncertainties of flood forecasting and the levee’s geotechnical integrity may be difficult to process. Probably without knowledge of what it would be like to live under such conditions, some people appear to have a greater tolerance of isolation without essential services.

Good, bad and ugly: exploring evacuation compliance, Murrumbidgee region flooding, March 2012 2018 Floodplain Management Australia National Conference, Gold Coast

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Murrumbidgee River Basin

Evacuation compliance rate Figure 2: Evacuation compliance rates for Murrumbidgee region communities, March 2012 flood

Good, bad and ugly: exploring evacuation compliance, Murrumbidgee region flooding, March 2012 2018 Floodplain Management Australia National Conference, Gold Coast

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Figure 3: Factors influencing people’s evacuation behaviours

Method Information about evacuation behaviours in North Wagga Wagga, Wagga Wagga, Darlington Point, Hay and Urana in the March 2012 flood was obtained in a few ways:  15 interviews of personnel (mostly SES) acquainted with the flood operations  7 interviews of community members (but not at Darlington Point and Hay)  24 interviews of both personnel involved in the operations and community members in North Wagga Wagga and Wagga Wagga, as part of an oral history project on the March 2012 Wagga Wagga floods (SLNSW, 2013; Hone, 2013)  Media reports and social media posts  Community flood data questionnaires issued by the SES after the March 2012 flood, in which one question related to evacuation (but not at Darlington Point and Hay).3 It is acknowledged that the methodology lacks the granularity and reach required to fully discern people’s reasons for evacuating or not evacuating. This would require carefully designed community surveys. Administration of such surveys would likely be difficult six years after the flood. One measure of the effectiveness of evacuation is the rate of compliance with evacuation orders. This was estimated, since people often go to friends’ and relatives’ places and do not register their evacuation. Any evacuation rate less than 100% carries a risk to the residual population, who may be among the most vulnerable (e.g. Hurricane Katrina). Another measure of the effectiveness of evacuation is the timeliness of people’s evacuation, but only anecdotal information was available for this. Details about the levees, evacuation orders and responses are provided in Table 1.

Good, bad and ugly: exploring evacuation compliance, Murrumbidgee region flooding, March 2012 2018 Floodplain Management Australia National Conference, Gold Coast

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Table 1: Details about levees, evacuation orders and evacuation compliance, Murrumbidgee towns, March 2012 flood North Wagga Wagga

Central Wagga Wagga

Darlington Point (DP)

Hay

Urana

Levee type in 2012

Earthen levee, constructed 1991

Earthen levee and reinforced concrete wall, constructed 1960-62, raised 1974

Earthen levee, constructed pre-1950s floods

Earthen levee, constructed pre-1950s floods, raised pre-1974 and 2012 floods

Non-engineered earthen levee (history not known)

Levee design level (to local gauge) in 2012

9.9m

10.7m

7.0m North DP Levee threatened DP

8.0m Hay 8.15m South Hay

Not known in 2012

Lowest crest level (to local gauge) in 2012

10.2m (i.e. 0.3m freeboard)

11.0–11.8m4

About 8.0m at lowest point

8.93m in 2011 9.5m pre-2012 flood

Not known in 2012

BoM flood prediction that triggered Evacuation Order

9.6m around 12pm Mon 5th Mar; 10.0m Tue night

10.8m around 7am Tue 6th Mar

Peak near 7.7m Sun 11th Mar

Exceed 8.1m Sat 17th, reach 8.9m Sun 18th night, peak near 9.0m Tue 20th

Not applicable

Evacuation Order issuance

6pm Sun 4th Mar 2012 (preceded by community meeting at 430pm)

9pm Mon 5th Mar 2012

Sat 10th Mar 2012

Thu 15th Mar 2012

7pm Mon 5th Mar 2012

Driver for Evacuation Order

Above design height of levee

Above design height of levee; concerns about levee integrity

Above safe working height of levee; doubts about levee strength

Above design height levee; no assurance levee top-up would hold; long duration of flood exerting pressure

Potential failure utilities

Population subject to Evacuation Order in 2012

~600

~8,000

~1,000

~2,000

~300

Estimated % compliance with Evacuation Order

>95%

80-90%

80-90%

40-50%