Related - Floodplain Manager October 2019

Warragamba Dam Flood Mitigation Inquiry Continues

A NSW parliamentary inquiry into the NSW Government’s proposal to raise the Warragamba Dam wall by 14 metres continues, with a public hearing set for 25 November.

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The World Heritage Committee raised concerns with the plan at a UNESCO meeting in Azerbaijan in July (FM July 2019).  A parliamentary standing committee was established to inquire into and report on the NSW Government’s proposal to raise the Warragamba Dam wall including: addressing conflicting reports on storage capacity and flood mitigation benefits of raising the dam; development on flood prone land; engagement with the World Heritage Committee; the adequacy of the environmental impact assessment in terms of aboriginal heritage; world heritage; ecological values; prospect of alternative options; flood risk assessment and management measures; cost of project; and implementation of measures outlined in the report for the inquiry into the Water NSW Amendment (Warragamba Dam) Bill 2018 dated October 2018. There have been 379 submissions made to the inquiry to date, and the committee has considered a wide range of concerns that were raised by stakeholders. The inquiry is unlikely to reach a rapid resolution as several hearings have been planned spanning into March 2020 (Read here and here).

Climate Change Challenging Emergency Services

The increased severity and frequency of weather events under a changed climate is a source of concern for Queensland’s Fire and Emergency Services (QFES).

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The devastating floods that struck North Queensland earlier this year killing three people and500,000 livestock and damaging 3,000 properties (FM Feb 2019), serve as a warning of what may happen more often according to the QFES. During the year, QFES identified several key issues in its annual report including the impact of climate change, the changing needs of an ageing and geographically dispersed population, and creating “more flexible strategies” to attract, keep and support volunteers. QFES also identified a need to adapt its service delivery model due to “increasing complexity” of the operating environment, as more frequent and severe weather events are predicted in the near future (Read here).

SMEs Shun Flood Cover

In the wake of the Townsville floods, issues which plague the commercial insurance industry have resurfaced.

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Small and medium-sized enterprises (SMEs) that were hard hit by the Townsville floods in January and February this year highlight issues in commercial flood insurance policies. These policies in areas of high-risk are not widely taken up by businesses which attempt to avoid price increases triggered if flood is included in policies. A spokesperson for the Insurance Council of Australia (ICA) states that commercial insurance is too costly to begin with and can be exacerbated by rising water damage repair costs, and the impact of unethical claims preparers. The only way to encourage SMEs to acquire flood insurance according to ICA’s Karl Sullivan, is to reduce flood risk in order to reduce the cost of insurance products (Read here).

Climate Risk Analysis Shows Australian Households in the Insurance “Red Zone” is Likely to Increase by 2100

An Australian climate risk analyst has calculated how changing climate risks such as bushfire, flood, subsidence, inundation and extreme wind, would impact the cost and availability of insurance by the year 2100.

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Karl Mallon of consultancy Climate Risk has undertaken an analysis which defines a property as effectively or potentially “uninsurable” when climate risk is so high that either insurers refuse to offer cover or the annual premium is priced at or above 1% of the cost to replace the property. Under this definition, it is estimated that the number of “uninsurable” addresses in Australia is projected to be 1 in 20 by the turn of the century. In 2018, two of the big four banks, Westpac and Commbank, used Mallon’s data to undertake detailed analysis of the physical risks of climate change to their property and insurance portfolios. Commbank’s findings projected a 100-fold increase in “high-risk” mortgages linked to rising insurance premiums, bringing its share of high-risk properties to 1% in 2060. Mallon’s analysis has been used to deduce climate risk in terms of property damage by combining climate change predictions and five hazards with area specific information such as flood maps, and condition of the building or dwelling. This is then used to calculate the probability of property damage from climate change and extreme weather for every address in Australia (Read here).

Government Reserves $50 million for Australia’s Flood Mitigation

The Morrison government's emergency response fund bill passed the upper house on 17 October after Labor struck a $100 million deal to support it.

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The extra funding will be drawn from the Emergency Response Fund, which was announced in the 2019/20 budget (FM May). According to office of Finance Minister Mathias Cormann, the funding will add to “support strategies available including pre-disaster and emergency preparedness initiatives, additional recovery grants, economic aid packages and support to affected communities or industry sectors to help respond to and build resilience to natural disasters”. The ICA has praised the decision vowing to assist in mitigation action plans, and decrease premiums where effective mitigation measures are in place to build more resilient communities (Read here).

Surviving a Crisis: Getting Through When the Worst Case Scenario Hits

The Townsville floods forced the energy utilities to put into practice the disaster plan designed to be deployed in a time of crisis.

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Energy Queensland’s Ergon Energy and Energex have shared the challenges they faced and steps taken to restore electricity supply during the February floods, as 17,000 were left without power. Prior to inundation, the action plan unfolded with heavy reliance and guidance by emergency services and weather reports. Ergon began the pre-emptive de-energisation, informing customers of outages, dismantling and removing vital equipment such as switchgear and SCADA systems from substations in the firing line, and sandbagging equipment that couldn’t be readily shifted to higher ground. Around 50% of Townsville’s flood-affected areas were supplied by an underground network which would have to be methodically opened, cleaned, tested, repaired and dried before being safely re-energised. However, as much of the area was cut off by floodwaters the clean-up effort was time dependent, and relied on regular aerial inspections to identify safe access points. Ergon stated that efficient communication with customers and stakeholders was crucial and that “the meticulous planning, resourcing and restoration planning, combined with outstanding commitment from staff, saw this result achieved without a single recordable injury”(Read more here).

Below Average Western Australian Cyclone Season No Excuse for Complacency

The Bureau of Meteorology (BOM) modelling suggests there will be fewer cyclones in the 2019–20 season, but the significant risk of at least one severe system making landfall remains.

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These predictions eerily echo those of last cyclone season which saw Tropical Cyclone Veronica cause widespread flooding and evacuations as it crossed the Pilbara coast in March (FM March, 2019). Between November and March the north-west coastal region of Western Australia experiences, on average, five tropical cyclones every season. Although this season is predicted to have a 40% chance of an above average number of tropical cyclones, the BOM has urged preparing early including stocking drinking water and non-perishable foods for up to five days, and remain attentive to community warnings off the north-west coast (Read more here ).

Micro-tunnelling Solution to Flood Risk

An innovative solution has been employed at Sydney’s Green Square to combat flooding.

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Green Square was historically a wetland which drained into the Botany Aquifer and the Cooks River. As a result of rapid urbanisation as Sydney expanded, the risk of flooding to residents was a concern. To address this, the City of Sydney and Sydney Water joined forces on the Green Square Stormwater Drain Project. The project came up with a micro-tunnel solution designed to reduced flood risk with minimal aesthetic and environmental impacts. The project consists of a 2.5km system of tunnels dug to a depth of 7-10m using a micro tunnel-boring machine. The tunnels divert stormwater to a mix of new and existing drainage systems, as well as harvest and treat runoff for non-potable uses. Vigorous testing of the capacity via hydraulic modelling with TUFLOW software, then with computational fluid dynamics preceded the construction of the channels to ensure optimisation. The system has been successful in its first year with noticeably reduced flood frequency in the area. The system’s accomplishment has been attributed to its low impact on residents and communities as it was able to be seamlessly integrated underneath existing infrastructure (Read more here ).

The Poor Have Higher Flood Risks

Research in the USA and Tanzania reveal that in both developed and developing countries, the poor tend to have greater flood exposure.

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A study in the USA analysed 40,000 records of flood-prone homes that were purchased by local governments with the help of FEMA since the late 1980s. Results showed that the counties that administer buyouts on average have higher income and population density. This is likely a result of unequal monetary resources between larger, richer areas and smaller, poorer areas to pay for the 25% balance left after FEMA’s buyout contribution. The study also indicates that poorer areas have fewer options in terms of investing in flood mitigation measures when compared to richer areas. As such, the benefits of buyout programs aren’t distributed evenly, often leaving the poor with no option to retreat from flood-prone areas or to employ flood mitigation measures.

Similarly, in Tanzania’s Dar es Salaam where at least 39% of the population has been impacted either directly or indirectly by floods, the poor are also worse affected during floods which frequently devastate the city (FM Sept, 2019). An analysis of three elements of flooding including exposure, vulnerability and socio-economic resilience, found that flooding effects were more severe on households that were more food insecure and had 14% lower per capita expenditures. Furthermore, affected households lost 23% of their annual expenditure following a flood, thus cumulatively the poor become poorer, and their capacity to recover is reduced with each flood (Read more here and here).

Can Drones Assess Flood Risks on Construction Sites?

A feasibility study shows that drones can be used to evaluate flood defence plans at construction sites and assess the impacts of earthworks on flood risk.

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Depending on topography and flood defences, the flood risk of construction sites can fluctuate during earth works. By coupling 3D topographical data with hydro-geological modeling software and rainfall simulation data, drones can be used to visualise water flow across a construction site or operational facility to determine the efficiency of site drainage and flood defence plans. To test this a pilot flight was conducted for a hydropower construction project in Angola. The survey considered flow velocity as determined by gradient, water volume, shape of the river’s channel and friction, and the placement of diversion tunnels and cofferdams. The simulation showed that the structures could withstand a 2% AEP flood. In the case of flash floods, rainfall data and expected construction related terrain changes were used to monitor the risk of flooding and landslides. Drone surveys demonstrated a cost effective, accurate and repeatable way of monitoring flood risk, and informing precise and timely placement of flood defences (Read more here ).

Can Farmers Fight Floods?

A meta-analysis of 89 studies across six continents has revealed the farming practices that can best increase water absorption and reduce flood risk.

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Researchers from the University of Nebraska-Lincoln analysed the effects of five emerging agricultural practices: no-till farming, cover crops, crop rotations, perennial plantings and cropland grazing and their efficiency in terms of water absorption. Results indicated that planting perennials such as grasses near cropland increases the rate of water absorption by an average of 59%, and planting cover crops boosted water absorption on average by 35%. On the other hand, rotating crops had no influence on water absorption rates, and allowing livestock to graze on cropland reduced water infiltration by an average of 21%. The common denominator in the most beneficial practices was the continuous presence of root systems as evident when planting cover crops, which is currently practised on only 10% of USA’s cropland. The study points to the need to focus on practices which increase water absorption rates thereby reducing flood risk in extreme rainfall events (Read more here).

Flood Mapping Using Flood Potential Index

A study published in the Journal of Water has found that combining the Flash-Flood Potential Index (FFPI) and the Flood Potential Index (FPI) in a model provides the best flood hazard maps.

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The study area was the Buzău river catchment in Romania, which is subject to frequent flash floods and riverine floods. Researchers identified areas vulnerable to floods and flash floods by computing the FFPI for the mountainous and the Sub-Carpathian areas, and the FPI for the low-altitude areas using four separate models. A database containing 168 historical flood locations and 172 areas with torrentiality was created and used to train and test the models. The models were run and tested using GIS techniques, and performance validation was obtained using receiver operating characteristic (ROC) curves. The best performing model was found to be the frequency ratio (FR) – Multilayer Perceptron Neural Networks (MLP) ensemble model (MLP–FR). The results showed that it is possible to obtain a detailed visualisation of the areas prone to floods and flash floods through Machine Learning techniques and statistical methods. By combining both the FFPI and FPI through the spatial correlation of flood and flash flood conditioning variables, decision makers can assess the zones prone to these types of natural hazards (Read more here ).

Machine Learning for Generalisable Prediction of Flood Susceptibility

New research has combined multi-basin flood prediction with statistical models and machine learning techniques to provide high quality and standardised flood susceptibility models.

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Traditional physics-based flood models are often expensive to calibrate and are rarely generalisable across various river basins. This is because site-specific parameters and human-regulated infrastructure are responsive to model performance. On the other hand, through the data on which they are equipped, statistical models implicitly account for such factors. The need for comprehensive in-situ measurements could be minimised by such models trained primarily from remotely sensed Earth observation data. In this study, the researchers used geographically distributed data from the USGS stream gauge network to establish generalisable, multi-basin river flood sensitivity models. Machine learning models were equipped to predict two flood susceptibility measures in a controlled setting from a combination of river basin features, impermeable ground cover data from satellite imagery, and historical records of rainfall and stream height. The results showed that machine learning models outperformed a random baseline classifier that assigned a random probability of flooding (Read more here ).

River 'Reset' to Reduce Flood Risk

A scheme is being run by the UK’s National Trust in conjunction with “Interreg 2 Seas Co-Adapt”, to “re-meander” a river to improve the diversity of flora and fauna and reduce the risk of flooding.

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The scheme which is inspired by similar projects in the USA, aims to restore the natural path of the River Aller in Exmoor in England’s south west. Earth moving works have begun to encourage the flow of water through multiple channels, pools and shallow riffles, as was the historical state of the river prior to drainage measures that placed focus on maximising grazing area and a singular river channel. These measures are designed to increase areas of wetlands and pools which in turn could encourage the return of water-dependent fauna such as wading birds and water voles. Furthermore, it is hoped that a return to the branching system would decrease flooding, as water and sediment will be stored and deposited instead of rushing rapidly through a catchment (Read more here ).

Flood Trends in Europe: Are Changes in Small and Large Floods Different?

A study published in Hydrology and Earth System Sciences has found variation in the magnitude of flood quantiles across Europe according to location.

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Reflecting on recent studies which revealed evidence of trends in the median or mean flood discharge in Europe over the last five decades (FM Sept 2019), this study assessed whether trends also occurred for larger return periods accounting for the effect of catchment scale. Researchers analysed 2,370 flood records spanning from 1960-2010 and catchment areas ranging from 5 to 100,000 km2 to estimate flood trends. A non-stationary regional flood frequency approach allowed the quantification of regional trends for three regions where coherent flood trends had been identified in previous studies. Similarly, this study found that trends were significantly different across the Atlantic region, Mediterranean region, and Eastern Europe. For example, the results show that in the Atlantic region, the trends in flood magnitude are generally positive, whereas the opposite was observed in the Mediterranean. Furthermore, in the Atlantic region the 1% AEP flood increases more than the median flood in small catchments (up to 100 km2) which directly opposes the trends observed in the Mediterranean region (Read more here ).

Building Rhino Flood Refuges

Artificial highlands are being built in India’s Kaziranga National Park to provide refuges for animals caught in flood waters.

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Kaziranga is home to 2,400 greater one-horned rhinos making it the world’s largest population. The park is also subject to large scale annual floods that are being exacerbated by increasing tourism infrastructure development within the park. Historically, animals facing floods in the park would flee to the higher ground of the nearby Karbi Anglong hills. However, animal corridors are now blocked by a highway and growing number of hotels and resorts. Approximately 200 animals were killed in the park during this year’s floods including 12 rhinos (FM July). Dozens of deer were also killed as a result of vehicle strikes whilst crossing the highway. Furthermore, construction of embankments has altered the riverine flow in the Upper Assam River causing greater sedimentation and increasing flood extremity. In response, park officials have created artificial highlands within the park which have been carefully placed to avoid blocking water flows. Early results suggest that rhinos have used these refuges, and it is hoped that this solution will decrease animal flood fatalities in the park (Read more here ).

Artificial Intelligence (AI) Enables “Smart Sewers” to Redirect Water to Reduce Flooding

The University of Sheffield, UK has created the CENTAUR system (Cost Effective Neural Technique to Alleviate Urban flood Risk), which can effectively manage the flow of water in cities, but is not without its challenges.

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The systems operates by installing “gates” in the sewer network which control water flow around the network which is monitored by water level sensors on either side of the “gates”. The systems can therefore detect rising water levels and open or close gates accordingly to redirect water to parts of the network with spare capacity thus preventing water overflow onto streets. The AI component of the system uses fuzzy logic to interpret uncertain conditions, such as the actual water level, and make decisions independently of humans, whilst learning from past mistakes. Although the system is relatively low cost and has had success in international trials, there may be some limitations in capacity during large floods, and ability to priorities flood areas. For instance, the best redirection of water in terms of the network may not equate to a decrease in danger to people, property and key infrastructure (Read more here ).

International Floods

There were 34 international floods reported across 31 countries throughout October 2019. At least 200 people died and over 51,000 were displaced.

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Internationally significant floods included:

South Korea

At least 10 people have died as a result of torrential rain, flooding and landslides brought by Typhoon Mitag early this month. The typhoon swept across the south east of the country bringing heavy rainfall including 67.4 mm of rain per hour in Donghae, Gangwon Province, marking the highest figure since 1992. More than 1,500 people were evacuated from the worst affected regions, and whilst the storm has dissipated as of 3 October, many people are still missing. (Read more here).

Japan

Typhoon Hagibis was one of the strongest tropical cyclones to hit the Kantō region of Japan since 1958. The region had been recovering from Typhoon Faxai just one month before. At least 80 people have died and 135,000 people were displaced as Hagibis brought greater than 550mm of rain in a 24 hour period in 10 locations in the region. Flooding from the Chikuma river in Nagano Prefecture inundated houses along its banks with a further 142 rivers across 15 prefectures standing above danger levels, and levees at 10 locations along nine rivers collapsing. The widespread flooding caused by Hagibis across central and eastern Japan, has resulted in an estimated $13 billion in damage to infrastructure and housing. (Read more here and here).

Tanzania

Heavy rainfall and flooding in the Morogoro region from 12 October has left 300 families displaced and at least 11 people dead of which five were primary school students. On 13 October, heavy rain damaged roads and submerged bridges in parts of Pwani and Tanga regions. Studies suggest that exposure to flood is widespread in Dar es Salaam, Tanzania’s most populous city (FM Sept, 2019) with 39% of the population or 2 million people being impacted either directly or indirectly by floods in the city. (Read more here).

Ethiopia

Heavy rainfall in southern Ethiopia has triggered landslides which have claimed the lives of 23 people and left 1,000 displaced. Search and rescue operations are underway as numerous homes were flattened by the landslides. (Read more here).

Ghana
Widespread flooding following heavy rainfall in Ghana’s Upper East Region has left 29 people dead and thousands displaced. The Tono Irrigation Dam overflowed leaving 844 hectares of farmland under water in Kassena-Nankana Municipal. (Read more here).

Russia

At least 15 people have died after a dam collapsed in Schetinkino in the Krasnoyarsk region of Russia on 19 October. The dam is located at a technological reservoir of a gold mining cartel, and rescue teams have been deployed to search for as many as 80 people believed to have been residing in temporary dormitories close to the mine. (Read more here).

Niger

Flooding from the Komadougou River in the Diffa Region has displaced 23,000 people. Across the region crops, farmland and homes have suffered damage with some villages on the outskirts of the city of Diffa becoming completely submerged. The latest floods have added to widespread devastation across Niger, as ongoing floods have resulted in 57 deaths and affected 132,528 people in the past months (FM Sept, 2019). (Read more here).

Diary

Young Floodplain Managers End of Year Event
Where: Sydney
When: 6:00pm- 9:00pm, Tuesday 12 November, 2019
Register 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

Global Flood Exposure Map

Global Flood Map allows users to view the flood exposure for any location in the world. In addition to historical flood data, the Global Flood Map is derived from physically based hydrology and hydraulic scientific data, which accounts for variable external factors such as rainfall, evaporation, snowmelt and terrain. The Global Flood Map currently displays high (1% AEP) and moderate (0.2% AEP) hazard flood zones via a 90 x 90 meter grid. (Click here).

Immersed: FEMA’s Flood Risk Visualisation Immersive Virtual Reality Tool

‘Immersed’ places the viewer in a virtual reality and simulates different flood scenarios effect on an unprepared community. The scenarios are then replayed, however this time mitigation action projects, such as installing proper drainage systems or porous pavements in areas with a flood risk are implemented to prevent the worst case scenario from occurring again. (Click here).