Related - Floodplain Manager April 2020

Australia Floods

Heavy rainfall on 3 April caused flash flooding in the Bendigo region of central Victoria trapping people in vehicles and damaging buildings.

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According to the Bureau of Meteorology (BoM) Bendigo Airport received 47.2 mm of rain in 24 hours (3 April) which led to flash flooding and cut the Calder Highway from Bendigo through to Wedderburn. VicEmergency sent out minor flood warnings on the morning of 4 April as the Campaspe River at Redesdale neared the moderate flood level of 4 metres. Victorian State Emergency Service (SES) responded to over 20 call-outs to building and flood damage, as well as several vehicle rescues. Wet and windy conditions were experienced elsewhere in the state, including Ballarat, as the SES received 278 calls for assistance in the 12 hour period from 3 April

(Read here, here, here, here, here, and here).

Actuaries Back Pre-Disaster Funding as the Royal Commission Commences

The Actuaries Institute has backed a proposed balancing of pre- and post-disaster funding to increase focus on mitigation and adaptation.

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On 20 February, 2020, a Royal Commission into National Natural Disaster Arrangements was launched in the wake of the devastating summer 2019 bushfire season.  Although it was prompted by the bushfires and is colloquially referred to as the Bushfire Royal Commission, its scope is all natural disasters, including floods.

Prime Minister Scott Morrison released the terms of reference which were informed by feedback from states and territories and highlighted three key national focus areas. The focus areas were identified as: improving natural disaster management coordination across all levels of government; improving Australia’s preparedness, resilience, and response to natural disasters, across all levels of government; and the legal framework for the Commonwealth’s involvement in responding to national emergencies and how that works with state and territory legal frameworks. Individuals, organisations, community groups and the broader community were invited to make submissions to assist the Royal Commission with submissions closing 28 April, 2020. The institute’s Australian Actuaries Climate Index Lead Actuary Rade Musulin said: “the inquiry (is) a “positive step” in allowing discussion on the mitigation action Australia will need to confront the climate challenge”. The inquiry which will: “investigate the losses that Australians have suffered and how those can be mitigated or prevented in the future” is poignant after the 2019 summer which saw $904 million in storm and flood insurance claims since September. The final report is due by 31 August  2020 (Read here, here and here).

Climate Change is Altering the Geomorphology of Australia’s Inland Rivers

Researchers from Macquarie University, Sydney have found that reduced stream flow predicted under a changed climate will modify the physical structure of Australia’s rivers.

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The study characterised 29 inland rivers across an aridity gradient from humid to arid, and as one of five alluvial river types from through-going, single channels to discontinuous, and multichannelled systems. The researchers then applied the projected aridity increase expected by 2070 to examine the effects it had on the rivers. It was found that 80% of the rivers would cross the threshold from one alluvial type to another, manifesting in major geomorphological changes. For example, predicted reduced flow in the Upper Murray, Mitta Mitta, Kiewa, and Ovens rivers in Victoria would increase sediment deposition in the downstream Murray thus reducing its size. The overall implications of the study is that wetland ecosystems that rely on periodic flooding such as the Lake Eyre basin, and farmers who rely on river flow for irrigation may experience reduced water availability predicted under a changing climate(Read here).

Varying Approaches to Enhancing Melbourne’s Urban Flood Resilience

An article published in Philosophical Transactions has explored urban flood resilience in Elwood, Melbourne using an interdisciplinary and catchment-based approach.

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Elwood was selected as the study site as its physical location makes it vulnerable to both pluvial and coastal flooding. The researchers combined methods from multiple disciplines including social science, urban design and environmental engineering to determine tailored strategies for the Elwood community to build urban resilience. The results showed that the best approach to resilience was an integrated conceptual framework which combined community engagement strategies such as workshops, urban design options such as green defences, flood risk governance strategies such as maintaining effective community dialogues, and engineering modelling and analysis techniques such as 1D2D2 flood modelling to assess flood risks (Read here and here).

Paradise Dam Preparedness Review Released

The 2019-2020 review was released in December 2019 and covered dam safety and risk-related issues, disaster management arrangements and community readiness.

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In September 2019, the Inspector-General for Emergency Management, Alistair Dawson was instructed to undertake the Paradise Dam Preparedness Review by the Minister for Fire and Emergency Services, Craig Crawford. The purpose of the review was to provide assurance about capabilities and community readiness for any future flood event, and to help strengthen local and district disaster management arrangements with relation to the dam. The dam, which was constructed in 2005, has long been at the centre of safety concerns particularly after it suffered significant damage following the 2013 flood. The review considered a variety of data including comprehensive flood studies, modelling and mapping, evacuation planning, and community surveys undertaken in the Bundaberg and North Burnett regions in Queensland. It was found that while current strength of the Paradise Dam spillway is calculated to be well below safety guidelines, the North Burnett and Bundaberg regions have suitable disaster management plans relating to flooding of the Burnett River system or associated with the Paradise Dam. Furthermore, the dam operator, SunWater had addressed all actions from a 2013 review and had taken necessary arrangements to reduce the risk associated with the low spillway strength. The review made 17 recommendations including that dam failure should be included as a separate risk within the local and district disaster management plans for North Burnett and Bundaberg regions (Read more here).

Social Distancing vs Flood Evacuation Psychology

Preventative safety measures employed during the COVID-19 pandemic have shed light on psychological principles which similarly manifest themselves within the natural disaster response context.

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The public response to practicing social distancing during the recent COVID-19 outbreak has demonstrated striking psychological response parallels to those observed during flood and hurricane evacuations. The psychological principle of “delay discounting” explains that people prefer a smaller immediate reward to a larger distant reward. In terms of practicing social distancing many may not perceive the immediate discomfort and economic insecurity as a preventative measure to unmitigated transmission, as if implemented correctly, social distancing lessens the threat and overall negative experience. The same is observed when evacuations are ordered ahead of a storm or hurricane, only for the event not to cause the fatalities or damage observed in disasters such as Hurricane Katrina, simply because preventative measures were deployed as intended. Furthermore, the notion of normality bias refers to underestimating likelihood of a disaster and its possible effects. People are more likely to become complacent or reluctant to evacuate during a hurricane if they have experienced and survived a similar event before, even if the risk is higher, for example  an impending Category 5 Hurricane as opposed to the Category 4 which they survived (Read more here).

Flood Adaptations in Europe’s Big Cities

Adaptation policies to changing flood regimes across Europe rely on climate data at a city level.

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Changing flood regimes across Europe as a result of climate change have been at the forefront of several recent studies. Increased precipitation predicted under a warmer climate according to one study will see 85%of cities on rivers in the UK facing more floods by the second half of the century. Furthermore, sea-level rise and storm surges will expose low-lying areas of European cities to coastal flooding. One study predicts that annual average losses from coastal flooding in 17 of Europe’s coastal cities might increase from $1.6 billion in 2030 to $52 billion in 2100. Although the observed effects of climate change may vary according to location (FM March, 2020), overall exposure and damages from flooding are predicted to be three to six times greater across Europe without adaptation measures in place. In response, the Copernicus Climate Change Service has developed a catalogue of extreme precipitation events at a city level using past data and, where possible, is linking extreme events with damages. One tool included in the catalogue is JPI’s FLoodCitySense which is an early warning service for urban pluvial floods that uses crowdsourced data to monitor rainfall and flooding to inform adaptation measures and reduce damages. Additionally, the European Flood Awareness System monitors and forecasts river floods throughout the continent and can forecast floods between three and ten days in advance. The collaboration of adaptation tools and resources have been utilised in climate proofing measures in Rotterdam which uses precipitation data and flood prediction tools to better inform its flood defences such as underground water storage reservoirs, blue-green corridors, and land port extensions (Read more here ).

Soil Science Informs Flood Mitigation 

In the wake of severe storms which brought catastrophic flooding to the UK, nature based solutions have been brought to the fore, including the absorbance capabilities of soil.

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Floodplains which served as soil sponges to excess water flowing from rivers and once covered much of the UK’s countryside now account for only 11% of English and Welsh floodplains. Wet woodlands, neutral grasslands, fens and marshes have been progressively replaced by intensive agricultural land covering 70% of the UK’s floodplains. As a result of vegetation clearing, soil compaction by heavy machinery and sediment runoff; the water storage capacities of soils in the UK have been compromised. According to research, there is between three and 10 times more water runoff from compacted soils than healthy soils which results in greater flood risk to downstream communities as water runoff increases river flow. Natural flood-management techniques have been favoured recently and involve reinstating features that were once common to fields such as ponds, hedges and leaky dams as well as creating buffer strips, wooded areas, drainage ditches and re-meandering rivers. For example in 2015, the Lake District village of Glenridding was adversely affected by Storm Desmond as flooding became exacerbated by the lack of soil absorption in surrounding farmland. To mitigate future losses, a local flood action group in collaboration with local farmers and the Environment Agency, re-meandered the river upstream of the village to create a flow release channel designed to reduce flood risk caused by compacted soils (Read more here) .

The Ecosystem Impacts of Flooding

Continued flooding of wildflower meadows and rivers in the UK is having disastrous effects on the ecosystems which rely on them.

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In the south west of England, the 120 hectare Lugg and Hampton meadows which is a site of special scientific interest bordered by the River Lugg and the township of Hereford, has been continually flooded since October 2019. Months of stagnant floodwaters which have inundated the once wildflower plentiful meadows are a source of concern for the Wildlife Trust which fears that many species of flora and fauna are at risk of decline or extinction. The anoxic environment caused by the floodwater may decimate populations of rare and endemic species such as vernal grass and the red-shanked carder bee making way for more resilient and invasive weed species. The indirect effects of increased flooding can be far reaching, as otters living in the River Lugg are killed in road collisions after being forced away from their traditional river bank homes which are being increasingly inundated. Elsewhere, soil runoff from surrounding agricultural land has seen as much as 200,000 tonnes of soil enter the river system during one flood in 2012. The soil saturation of rivers causes erosion of sediment deposits which are important fish spawning habitat. For instance, a flood in 1977 washed away salmon eggs which have had long term effects on fish populations nearly 25 years on. As such, the need to protect the rivers systems and the wildlife that call it home is becoming increasingly apparent as prolonged and frequent flooding increasingly occur (Read more here).

Community Flood Resilience Measures Encouraged

The Calder Valley is hailed as the 'rapid response catchment' and is the most flood-prone region in the UK, as such community flood resilience action is both encouraged and lifesaving.

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The town of Hebden Bridge in the Calden Valley experiences flash flooding with little warning with the worst experienced on Boxing Day in 2015 when thousands of dollars of damage was caused by destructive and quickly dissipating river water. The town has 15 flood wardens who continually encourage the community to take preparatory, defensive action particularly before large storms. One warden, Andrew Entwhistle said that to prepare the community for a potential flood “we look for trigger points, such as the height of the river or the rate of water flow”. The warden alerts community volunteers of potential hotspots of riverbank weakness to install rubber diversion bricks to protect the village. These measures physically protect the village and afford the community more time to prepare. Additionally, community members are encouraged to maintain an active dialogue with the flood warden to report any pooling water on their property which might be a first indicator of an impending flash flood. Furthermore, a National Trust backed community initiative called Slow the Flow has built more than 500 “leaky dams” which are a nature-based alternative to traditional defence structures and help to reduce peak flow (Read more here).

Gender-Aware Flood Early Warning Systems

Research in Nepal has explored the interaction between gender and flood early warning systems (EWS) to identify ways at reducing the vulnerability of marginalised gender groups.

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The study focused on five aspects of an EWS where gender is most influential: vulnerability, participation, dissemination, response, and power and decision making. Interviews were conducted with 92 women and 35 men, 11 focus groups were held and another 28 vulnerable or marginalised women were also interviewed. It was found that 94% of respondents believed that women are more impacted by flooding than men, and this is predominantly due to cultural, economic and information accessibility factors. For example, the primary source of communication of flood warnings was via SMS, however, many women did not have access to this resource due to monetary or cultural reasons. As such, flood communication and EWS should consider this factor and create more readily accessible alternatives. Furthermore, 74% of respondents stated that response and evacuation procedures were something that men are more often educated in, whereas women are not expected to possess this knowledge. This dependency on men to provide disaster decision making was identified as an issue to be addressed when developing EWS in order to encompass women in preparedness activities and evacuation decisions (Read more here ).

Early Warning Systems for Storm-Wave Flooding

Researchers of an article published in the Journal of Frontiers in Marine Science have identified a method to create an Early Warning System (EWS) for storms and scenarios specific to coral reef-lined coastlines.

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Traditional modelling tools used to develop EWS are based on open-coast sandy shorelines and often fail to incorporate variables such as  local sea levels, offshore waves, as well as their near shore wave transformation associated with coral reef lined shorelines. In response, the Understanding Flooding Of Reef-lined Coasts (UFORiC) group has been established to address current EWS shortcomings. UFORiC identified several gaps in currently available data tools which should be addressed to create an EWS for coral reef-lined coasts including: better coverage with wave buoys particularly in the southern hemisphere; more historical analyses of floods and impacts to validate EWS; and better utilisation of high spatial resolution bathymetry and topography maps for wave modelling and forecasting of absolute flood levels and extents. Creating an EWS tailored for coral-reef lined coastlines is pivotal as coastal flooding is expected to become more frequent and severe due to sealevel rise putting many coastal cities and communities at risk (Read more here.)

Communicating the Efficacy of Flood Mitigation Plans

A collaborative project between researchers from France and the UK has produced a graphical approach to communicating flood mitigation options.

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The graphic is designed to communicate complex ideas and concepts relating to flood mitigation in a more rateable way which goes beyond relying on mathematics and equations. The case study used for the graphic was the Leed’s Boxing Day 2015 floods which occurred after the River Aire burst its banks causing $950 million worth of damage. The researchers calculated the flood-excess volume (FEV) of the river during this event as approximately 9.34 million cubic metres. This volume of water was translated into a hypothetical square lake, two metres deep and with sides of 2.16 km in length, upon which the graphic is based. The graphic presents several mitigation scenarios such as building higher flood walls and removing river obstructions and presents their costs and their impact on river dynamics. Lead researcher Professor Onno Bokhove said: “Our approach is intended to offer a means of comparing and choosing between flood-mitigation scenarios in a quantifiable and visual manner” which can be “better understood by a wide audience including the general public, stakeholders and planners” (Read more here).

Quantifying Resilience Provided by Hydraulic Structures

An article published in WIREs Water has explored the application of facets of resilience in the design of hydraulic structures.

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The author proposes three resilience approaches: level 1 -the qualitative selection of components; level 2- the reassessment of urban flood resilience on the basis of updated historical flood records; and, level 3-the quantitative comparison of resilience values for different hydraulic structures. Level 1 resilience describes the way that hydraulic engineers designs structures such as dam spillways to absorb the loads even within a certain overload range thus increasing resilience. Level 2 resilience is quantified by a set of multicriterial indicators such as impact and damage costs should the structure fail, availability of disaster relief units, and insurance coverage. Level 3 refers to the notion that resilience itself can act as a design criterion calculated by known impact, affected area, damage consequence, and time to recover. The author found that the level 2 resilience method is most helpful for the design, operation, and inspection of technical works and structures because input data is more readily available and is not reliant on purely descriptive resilience measures (Read more here ).

How the Interdependency of Critical Infrastructure Can Determine Flood Resilience

Researchers from the University of Applied Sciences Cologne, Germany have assessed how Critical Infrastructure (CI) cascading effects aggravate flood risk.

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The study focuses on the city of Cologne which experienced several large-scale floods in 1993 and 1995, and the county of Rhein-Erft-Kreis. The researchers used GIS data on infrastructure, open source data from federal and local administrative agencies online platforms, and historical data from the 1993 and 1995 floods. The data was used to undertake spatial resilience assessments and explicit place-based assessments to identify CI such as roads, bridges and electricity substations that could be exposed to floods. The study found that the total length of road segments potentially exposed to floods was approximately 2,203 km. Comparing the flood impact on CI demonstrates that interdependencies and cascading effects persist between the flood as a stressor, and the affected CI assets. For example, the resilience of both emergency management and hospitals was shown to be dependent on the accessibility of the road network (Read more here ).

Role of Non-Linearity in Determining Flood Exposure and Loss

A Journal of Nature Communications article has demonstrated how accounting for non-linearity in coastal impact assessment diminishes coastal exposure and reduces global flood cost estimates.

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The researchers used data from 621 individual tide gauge stations to calculate total extreme sea-levels both with and without tide and skew tide independency, in order to compare the influence tide surge interaction (TSI). The results showed that at 90% of all surveyed stations the extreme sea levels were overestimated if TSI was not accounted for (i.e. without tide and skew tide independency). The implications of such findings are that non-linear impact assessment predictions result in a reduction of 17% in people affected, and reductions in direct flood costs by 13%. The study therefore provides an alternative way of accounting for TSI and can be combined with independent realisations of tide and skew tide, contributing to a more reliable and consistent risk and impact assessment(Read more here ).

Flash Flood Mortalities Determined by Environmental Settings

An article published in the Journal of Flood Risk Management has demonstrated that flash flood mortality characteristics differ substantially depending on the setting.

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The case study for this research was the 2017 flash flood of Mandra in Greece which led to the death of 23 people. The 2017 flood offers a unique opportunity as the flooding was caused by two tributaries of the Mandra River which have similar geomorphology, rainfall accumulation, time to peak, peak discharge and timing. Therefore, the researchers could examine the influence of the two contrasting settings (urban and non-urban) on flood mortality based on similar flash flood conditions. It was found that overall the victims of the flash flood in both settings were aged on average 65 years old and that more were male than female. The study also revealed that in the non-urban setting more people died in outdoor incidents including 15 in vehicle related incidents despite having significantly fewer vehicles than in the urban areas which had eight vehicle related deaths. This was attributed to the availability of alternative ways to safety in the urban context such as road detours which aren’t as readily available in the non-urban setting. The findings show that the surrounding environment has some part in determining flood mortality and should be considered in educational and community awareness programs which aim to reduce risk (Read more here ).

Flood Resilience in the Face of a Pandemic

The compounding effects of the COVID-19 pandemic and continual natural disasters are rapidly becoming a test of resilience.

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In 2019 alone, 14.7 million people were displaced by floods and storms, and as monsoon season and spring flooding nears in Asia and the USA many more people are likely to be affected. The COVID-19 pandemic is likely to compound existing risks and vulnerabilities to flooding and test the flexibility and resourcefulness of governments and humanitarian aid globally. For example, many of the responses during a flood such as community centres to shelter large congregations of displaced people are in themselves a risk as it presents an opportunity for rapid proximity-related disease transmission. Flood resilience measures must therefore consider factors likely to be at play during the current health crisis. For instance, pre-disaster education, preparation and resources should be tailored towards identifying likely vulnerable populations such as those with pre-existing conditions, and ensuring that health facilities have adequate PPE in case of outbreak (Read more here, here and here).

Flood Risk Management Influenced by Individual Expectations of Governance

An article published in the Journal of Flood Risk Management has explored the discrepancies between the expectations of responsibility-sharing, and the willingness for individual flood risk reduction.

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A survey of people from two flood-prone municipalities of Czechia was conducted to gather data on individual flood perception within the context of multi-level flood risk management governance. The results were classified into four levels of flood risk perception from low to very high. The people from the municipality which flooded most recently were 40% more likely to perceive their flood risk as high than the other municipality. In both survey areas, approximately 40% of respondents believe that flood damage could not have been avoided. However, those who believe it could have been avoided, were reluctant to take individual mitigation actions due to perceived costs. Additionally, 80% of all respondents agreed that the responsibility of flooding should be divided between at least two entities, but that citizen involvement should have the lowest responsibility. In this context, individuals perceive themselves as passive actors in multilevel Flood Risk Management, and there is a general expectation that governmental bodies are ultimately responsible, but this varies according to previous flood experience and perceived risk (Read more here).

International Floods

There were 27 international floods reported across 21 countries during April 2020. At least people 139 died and over 94,327 were displaced.

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Internationally significant floods included:

Pakistan

Heavy rainfall has caused widespread flooding across several provinces in Pakistan killing 33 people and injuring 54. A total of 127 homes were damaged and 13 were completely destroyed. (Read more here, and here).

Yemen

Significant flash flooding occurred in the city of Aden in Yemen when as much as 125 mm of rain fell in 24 hours on 21 April. At least ten people died and 30 were injured. Roads and other infrastructure were damaged and flood waters affected temporary shelters for families already displaced by conflict in the country. (Read more here and here ).

Democratic Republic of Congo

Torrential rainfall has reportedly caused 36 deaths and left 78,000 people displaced in the Democratic Republic of Congo. Uvira city experienced flooding from the Mulongwe River that resulted in the destruction or damage of over 15,000 homes and seven bridges. (Read more here and  here)

Papua New Guinea

The Zokozoi River in the Eastern Highlands Province of Papua New Guinea has flooded damaging or completely destroying at least 500 homes. Heavy rain also triggered landslides that killed at least ten people in Chimbu Province. These follow the deadly floods that occurred in late March (FM March). (Read more here and here)

Diary

Submissions Now Open for the Australian Institute for Disaster Resilience (AIDR) Resilient Australia Awards
Submissions close 18 May 2020
For more information visit here

2020 Floodplain Management Australia Remote Conference Dates Announced
Where: Online
When: 20 and 21 May, 2020
To register visit here, for more information visit here

2020 Association of State Floodplain Managers (ASFPM) Annual National Conference
Where: Fort Worth, Texas, USA
When: 7-12 June 2020
For more information visit here

2020 International Conference on Flood Management
Where: The University of Iowa, Iowa City, Iowa, USA
When: 17-19 August, 2020
For more information visit here

FRIAR 2020 International Conference on Flood and Urban Water Management (Postponed from original date)
Where: Valencia, Spain
When: 28-30 September
For more information visit here

Flood and Coast 2020 Conference and Exhibition (postponement date announced)
Where: Telford International Centre, UK
When: 8-10 December, 2020
For more information visit here

FLOODrisk 2020 European Conference on Flood Risk Management (postponement date announced)
Where: Budapest, Hungary
When: 21-25 June, 2021
For more information visit here

Resources

Tasmanian Flood Resilience Podcast

The “Stories of Resilience” podcast series is part of a suite of Resilient Hobart projects that aim to assist Tasmanian communities affected by the May 2018 floods with their journeys to recovery and with responding to future emergencies and disaster events. Community members from Hobart, Kingborough, Glenorchy, and Derwent Valley municipalities have shared their stories 12 months on from the 2018 floods to raise awareness about future preparedness and recovery efforts. (Listen here)

Conference Papers from FMA’s Canberra 2019 Conference Now Available

Conference Papers from FMA’s National Conference held in Canberra last year have now been released publicly. The conference theme was “A National Call to Action: Making Australia Flood Safe” and featured presentations by Molino Stewarts’s own Steven Molino (available here), Filippo Dall’Osso (available here), and Neil Dufty (available here). The full list of conference papers is available here.

Flood Resources for Schools

The US Association of State Floodplain Managers has collated a wide array of flood education materials for school children in kindergarten to grade 12. The resources include interactive games, decision based flood resilience simulations, preparedness and flood awareness worksheets and educational videos.(Click here).

Social Vulnerability in High Flood Risk Australian Communities

An article published in the Journal of Natural Hazards has found that social vulnerable populations are more likely to reside in high flood risk areas. The study areas of Murwillumbah and Lismore NSW, which are flood affected, included 47% and 60% of residents in the most disadvantaged quintile neighborhoods compared to 27% for whole region. The study highlights the compounding effects of social vulnerability factors and flood risk on already disadvantaged rural communities. (Click here)