Related - Floodplain Manager July 2019

Sydney Flooding: Worst-Case Scenario Would Affect 100,000 Residents, Modelling Shows

New modelling for the Hawkesbury Nepean river system shows a worst-case flood would affect 100,000 residents and see 12,000 homes going underwater.

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The modelling predicts that suburbs such as Richmond, Windsor and Penrith are among those most at risk from flooding.

Link to the Channel 7 news report can be found here.

A Land of Drought and Flooding Rains

An article by the University of Melbourne explains the interaction between increasing rainfall, dry soil conditions, and flooding.

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Trends show that severe rainfall events are becoming increasingly common under a warming climate and that they potentially result in increased flash floods. Conversely, in rural areas of Australia while rainfall events have increased, the magnitude of flooding has decreased. Researchers believe that this apparent paradox is influenced by the amount of moisture retained in the soil prior to a rain event. The study considered 213 catchments across Australia and combined data collected from stream-flow, rainfall, and soil moisture to investigate the resultant flooding by quantile regression analysis. The results concluded that average extreme rainfalls are increasing, whereas flood magnitude is decreasing on average at rate of 15 per cent per decade. This means that it is likely that larger flooding events will become more common and smaller events less prevalent due to drier soil conditions. Urban areas which tend to have less permeable concrete surfaces will experience greater flood events than rural areas where rain is able to soak more easily into the soil. The inter-relatedness of each of the study variables increases understanding of the consequences of climate change and how to prepare (Read here).

Warragamba Dam Threat to Blue Mountains

The plan to raise the Warragamba dam by 14 metres thereby placing extraordinary cultural and biodiversity value areas as risk of inundation has sparked concern among UNESCO’s world heritage committee.

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Warragamba Dam is Sydney’s main water storage dam, and is on a major tributary of the Hawkesbury Nepean River. The NSW government has proposed the raising of the dam wall vowing that it would create a flood mitigation zone which would temporarily hold back floodwaters and reduce flood levels downstream in outer western Sydney potentially reducing risk to 12,000 homes. The World Heritage Committee (WHC) at a meeting in Azerbaijan this month found that raising the dam wall is expected to increase the frequency and extent of upstream flooding in the Blue Mountains, which would impact on the “Outstanding Universal Values” of the site. The areas proposed for inundation if the dam is raised are in excess of 4,000 hectares of World Heritage Land and adjacent property and home to 40 endangered flora and fauna species and 300 known Gundungurra Aboriginal cultural sites. The UNESCO committee has asked the NSW government to submit an environmental impact statement for the project by December this year before any decision is made (Read here, here, and here).

Townsville Flood Victims Hit by Centrelink Robodebt Program

Flood affected residents of Townsville situations are set to worsen as Centrelink ramps up robodebt scheme.

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The scheme includes a tool which averages a welfare recipient’s employment income over an entire year to determine if they were overpaid. The tool is only supposed to be used when a recipient has not provided payslips or bank statements to calculate a potential debt. Flood affected areas in far north Queensland were initially quarantined from Centrelink’s welfare debt compliance activities. However, recently Centerlink has resumed compliance activities and is on track to issue 200,000 debts this financial year. This is a major source of concern among those affected by the February floods (FM March) which damaged more than 3,000 homes and killed three people. The difficulty for flood victims to provide evidence of their past employment income is exacerbated by the disaster, particularly as many people are still unable to return to their homes (Read here).

If your Coastal Home Could be Threatened by Flooding 80 Years from Now, Would you Want to Know?

The Noosa shire in Queensland has declared a “climate emergency” amid fears that 2,000 could be affected by storm flooding.

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he latest predictions from the Department of Environment are that under a high-end scenario, sea level s could rise 1.1metres and cost $226 billion nationally by the end of the century. This would place around 68,000 properties at risk in Queensland alone. The coastal Noosa shire has recognised the risk posed by predicted storm flooding which has prompted the shire to consider alerting current and future residents of properties at risk of flooding. The Insurance Council of Australia has stated that climate predicted flooding would not affect premiums, but storm and water damage would. Noosa Shire is therefore considering the feasibility of protecting at risk property, and alerting homeowners and possible buyers of flood risk through routine property or rates searches (Read here ).

New Vegetation Map to Help Victoria Manage Bushfires and Floods

Monash University researchers have developed Australia’s first high-resolution vegetation map, to assist with fire prevention, agricultural planning, flood modelling, pollution management, and mine site monitoring and rehabilitation.

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Data comprising of more than 4,300 images sourced from the European Space Agency’s Sentinel-2 satellite, has allowed researchers to develop a vegetation map of Victoria at 10metre spatial resolution. The algorithms utilised have identified to a fine scale vegetation land-cover such as vines, gum trees, pastures and grasslands, and crops. The map has wide reaching potential including in flood management such as predicting how much water is absorbed by the soil after rain based on the vegetation type. The unprecedented detail gained from this map could make it an ideal study to be replicated elsewhere in Australia. (Read here).

New Technology at Salt Creek to Reduce Flash Flooding Risk

Solar-powered cameras equipped with image recognition software have been installed at storm water grating in Melbourne to identify and reduce risks of flash flooding.

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Two cameras are being trialed in metropolitan Melbourne, Victoria to monitor litter and leaf buildup that increase the risk of flash flooding. There are approximately 400 grates across Melbourne that are regularly inspected and cleared by Melbourne Water staff, however conditions change frequently and a buildup of debris can occur between inspections and potential initiate flooding. The cameras offer an automated and continuous monitoring alternative enabling the rapid detection of debris buildup and a real-time blockage alert. If the trials prove successful, other high risk flash flooding sites across Melbourne may also receive the technology (Read more here).

Monitoring the Situation of the World’s River Systems in Real-Time

“Today's Earth and Today's Japan” is a joint research project between the Japan Aerospace Exploration Agency (JAXA) and researchers at the University of Tokyo which allows accurate real-time monitoring of the worlds river systems.

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The project which began in 2006 uses an Integrated Land Simulator (ILS) to make predictions based on the quantitative analysis of the movement of all water on the Earth. To this end, the system is able to monitor the world’s river systems from a global and even municipal scale with staggering accuracy. The capabilities of this tool were best demonstrated during the 2015 Kanto and Tohoku torrential rain event. The system was able to detect that the Kinugawa River may flood 39 hours before it did and made a highly accurate flood prediction 15 hours before it did. As climate change drives more frequent occurrences of extreme weather events, this project serves to provide greater accuracy and longer lead times for flood predictions on a global scale(Read more here ).

Parting the Waters of Uncertainty for Private Flood Insurance

A one sentence inclusion in insurance policy helps federally regulated lenders determine if flood insurance meets legislative requirements.

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Several pieces of legislation in the USA require flood insurance to be taken out on properties in the Special Flood Hazard Area (SFHA) for them to be mortgaged with a federally regulated lending institution. Until 2012, this insurance was required to be provided through the National Flood Insurance Program. Since 2012 lenders have been obliged to accept ‘private flood insurance’ as long as it meets certain criteria, however determining whether insurance meets that criteria has been confusing for lenders. This new rule simplifies the process somewhat, as lending institutions can now accept private flood insurance if the policy contains the following language: “This policy meets the definition of private flood insurance contained in 42 U.S.C. 4012a(b)(7) and the corresponding regulation” (Read more here ).

Rivers, Levees, Flooding, and Development Podcast

A podcast hosted by executive director of the Great Rivers Habitat Alliance David Stokes discusses key issues relating to flooding in a two part series.

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In part one of the series Stokes discusses the construction of levees. The podcast ruminates on the positive and negative aspects of levees and questions who is responsible for the flow on effects of their construction in the field of floodplain management. Part two focuses on the concept of the 500 or 100 year flood and queries whether it should in current times be more in the realm of 15 years, as well as measures to prevent devastating river confluence (Read more here ).

UK Tidal Flood Barrier Wins Top Engineering Award

The Ipswich Tidal Flood Barrier which protects over 1,600 homes and 400 businesses from the risk of flooding has won an Exceptional Merit Award from the Institution of Civil Engineers (ICE) East of England Merit Awards.

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The barrier is part of $125million Ipswich Flood Defence Management Strategy which comprises a mixture of new and refurbished walls and gates along 1.1km of the River Orwell. The 200-tonne rotating Radial Sector Flood Gate is similar in design to the Thames barrier in London and can be raised in minutes in the event of a tidal surge. The barrier is thought to drastically reduce flood risk as well as free hectares of land for regeneration (Read more here ).

Operational Methodology for Rapid Flood Inundation and Potential Flood Damaged Area Mapping

An article published in the Journal of Remote Sensing has proposed an operational methodology for flood mapping using multi-temporal Sentinel-1 SAR images.

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Bangladesh was used as a case study in this article as more than 80% of the country is flood prone and 20,000 deaths have been reported due to flooding between 1954 and 2007. Traditional methods of inundation mapping such as comparing water levels with national digital elevation models (DEM), and satellite-based monitoring are often confounded in Bangladesh by insufficient data and adverse weather conditions such as thick cloud cover. Therefore space borne synthetic aperture radar (SAR) systems are the preferred option for monitoring flood condition under adverse conditions. The researchers used Sentinel-1 SAR images from March, April, June, and August 2017 to generate inundation extents of the corresponding months. The overall accuracy of flood inundation mapping was 96.44% and the accuracy of the land cover map was 87.51%.Based on the Landsat-8 derived land cover information, the study determined that cropland damaged by floods was 1.51% in April, 3.46% in June, and 5.30% in August. The methodology outlined in this study is easily replicated and could be used in annual flood maps (Read more here ).

 

Assessing Catchment Scale Flood Resilience of Urban Areas Using a Grid Cell Based Metric

An article published in the Journal of Water Research has proposed a grid cell based resilience metric method of characterising urban surface flood resilience at the urban drainage catchment scale.

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Urban flooding has become a global issue due to climate change, urbanisation and limitation in the capacity of urban drainage infrastructures. By incorporating resilience in urban flooding assessment and management, existing drainage capacity of an area can be better utilised and investment can be focused on places that are less resilient to flooding. In this study, researchers used the two-dimensional grid cell based flood model Cellular Automata Dual-DraInagE Simulation (CADDIES) to investigate the ratio of unflooded grid cells to the total grid cell number in 31 urban drainage catchments in Dalian, China. The model was used to simulate surface flooding to assess flood resilience for urban surface flood management. The results showed that flood resilience is influenced by the joint impact of different urban drainage catchment characteristics such as different land cover percent-ages, catchment average slope and drainage capacity. Furthermore, the study was able to provide highly targeted modelling which revealed that broad sweeping adaptation strategies such as reducing the runoff generation from the upstream catchment alone may not be as effective as reducing runoff from downstream as well. The metric presented in this study allows for more tailored resilience strategies to be produced according to finer scale catchment characteristics (Read more here ).

Past 50 Years of Flood Data Used in New Statistical Model to Predict Flood Duration

Researchers from the City College of New York have developed a physically based Bayesian network model for inference and prediction of flood duration.

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The statistical model was tested using data from the Missouri River Basin area in the USA. Researchers found that long duration floods are dependent on high flow conditions in rivers caused by heavy rainfall, followed by a large long-lived low pressure system. The implications of these findings are that flood durations and extents may be more accurately predicted by using atmospheric dynamics and land surface condition data (Read more here ).

New Flood Prediction Technology Will Save Lives and Livelihoods Across the World

FloodMap Live is a real-time street level flood prediction technology developed at Loughborough University, UK which enables the timely assembly of flood defences in order to protect the population and critical infrastructure.

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Cities across the globe are increasingly vulnerable to surface water flooding due to rapid urbanisation, infrastructure developments and more intense rainfall resulting an estimated $1 trillion annual economic lost by 2050. Using a combination of modelling techniques researchers are able to deliver accurate, real-time flood occurrences and forecasts as well as street-level impact analytics. It is hoped that FloodMap Live will enable economic, environmental and population impacts of flooding to be mitigated, as well as inform emergency responses regarding accessibility of areas (Read more here ).

International Floods

There were 15 international floods reported across 14 countries throughout July 2019. At least 429 people died and over 3 million were displaced.

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Internationally significant floods included:

India

Torrential monsoon rainfall in north east India has caused flooding in several states, affecting over 4 million people, leaving millions displaced and at least 200 people dead. In the worst hit areas of Assam and Bihar 4.5 million people have been displaced with 100,000 people forced to live in relief camps. Flood waters have inundated road and rail infrastructure making disaster relief difficult. The floods have also affected nearby Kaziranga national park, one of the world’s most important wildlife parks and home to the highly endangered one-horned rhino. (Read more here, and here).

Myanmar

A period of heavy rain in northern and western Myanmar has caused rivers to overflow displacing 14,000 people. On 14 July, approximately 90mm of rain fell in 24 hours in Sittwe, Rakhine state, whilst Thantwe recorded 173mm during the same period.  (Read more here).

Nepal

In Nepal, monsoon rains have caused widespread flooding and landslides leaving 65 dead and at least 3,100 displaced. The country’s capital Kathmandu recorded 104 mm of rain in 24 hours. As of 15 July, the Tinaau river at Butwal was the standing at 5.21metres (danger level is 4.6m) and rising.  (Read more here).

Bangladesh

At least 37 people have died as a result of monsoonal rain and flooding across the country with the worst affected areas in Khagrachari, Netrokona, Lalmonirhat, Sunamganj, Bandarban, Cox’s Bazar, Chattogram,Sylhet, Rangamati, Gaibandha and Kurigram. Rivers in 23 locations were above danger level including the Sangu at Bandarban, Chittagong Division, which stood at 17.16 metres, when danger level is 15.25 metres. Near to the Sangu at Bandarban in the country’s south east, lie the Rohingya refugee camps where 50,000 people are thought to have been affected. Meanwhile in the countries north, the Jamuna River broke through an embankment, inundating at least 40 villages in the district of Gaibandha and displacing more than 200,000 people.  (Read more here and here).

Pakistan

At least 46 people have died as a result of flood-related incidents across the country this month. This includes at least 27 people presumed dead after flash floods in the Neelum Valley in the Pakistan-administered territory of Azad Jammu and Kashmir. Elsewhere in Punjab Province, Sheikhupura and Lahore, dozens of people have died as a result of house collapses as more than 150mm of rain fell in 24 hours. (Read more here and here).

Diary

Adapting Swansea: Planning for Future Flood Risks
Where: The Swansea Centre, 228 Pacific Hwy, Swansea NSW 2281
When: 4pm-6:30pm, 6 August, 2019
For more information visit here

2019 IMA International Conference on Flood Risk
Where: Swansea, UK
When: 12-13 September, 2019
For more information visit here

2019 International River Symposium
Where: Brisbane, Australia
When: 20-24 October 2019
For more information visit here

2019 The International Emergency Management Society (TIEMS) Annual Conference
Where: Goyang, Korea
When: 12-15 November, 2019
For more information visit here

2020 Floodplain Management Australia Conference
Where: Empire Theatre, Toowoomba, QLD
When: 19-22 May, 2020
website

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

Resources

Sea Level Rise Game.

LA times have released an interactive decision-making game in which the player is given a budget and must protect a beachside town from the threat of erosion and sea level rise using physical defenses, and community liaison tactics. (Click here).