GeoLog

flooding

Imaggeo on Mondays: Sedimentary record of catastrophic floods in the Atacama desert

Imaggeo on Mondays: Sedimentary record of catastrophic floods in the Atacama desert

Despite being one of the driest regions on Earth, the Atacama desert is no stranger to catastrophic flood events. Today’s post highlights how the sands, clays and muds left behind once the flood waters recede can hold the key to understanding this natural hazard.

During the severe rains that occurred between May 12 and 13, 2017 in the Atacama Region (Northern Chile) the usually dry Copiapó River experienced a fast increase in its runoff. It caused the historic center of the city of Copiapó to flood and resulted in thousands of affected buildings including the University of Atacama.

The city of Copiapó (~160,000 inhabitants) is the administrative capital of this Chilean Region and is built on the Copiapó River alluvial plain. As a result, and despite being located in one of the driest deserts of the world, it has been flooded several times during the 19th and 20th century. Floods back in 2015 were among the worst recorded.

The effects of the most recent events are, luckily, significantly milder than those of 2015 as no casualties occurred. However, more than 2,000 houses are affected and hundreds have been completely lost.

During this last event, the water height reached 75 cm over the river margins. Nearby streets where filled with torrents of mud- and sand-laden waters, with plant debris caught up in the mix too. Once the waters receded, a thick bed of randomly assorted grains of sand  was deposited over the river banks and urbanized areas.

Frozen in the body of the bed, the sand grains developed different forms and structures. A layer of only the finest grained sediments, silts and clays, bears the hallmark of the final stages of the flooding. As water speeds decrease, the finest particles are able to drop out of the water and settle over the coarser particles. Finally, a water saturated layer of mud, only a few centimeters thick, blanketed the sands, preserving the sand structures in 3D.

The presence of these unusual and enigmatic muddy bedforms has been scarcely described in the scientific literature. A new study and detailed analysis of the structures will help better understand the sedimentary record of catastrophic flooding and the occurrence of high-energy out-of-channel deposits in the geological record.

By Manuel Abad and Tatiana Izquierdo, Universidad de Atacama (Chile)

 

GeoSciences Column: Mapping floods with social media

GeoSciences Column: Mapping floods with social media

Picture this: you are on your commute home, smartphone or tablet in hand, surfing the internet. You might quickly catch up on the latest news, check in with your friend’s on Facebook, or take to Twitter to share a morsel of information with your followers.

This scenario is common in the modern era of technology. No doubt we are all guilty of indulging in a serious session of internet navigation every now and then (and nothing wrong with that!). But what if your online persona could also make a contribution to better natural disaster management?

One of the many challenges during, and in the immediate aftermath of, natural disasters is being able to provide local populations with timely and reliable information about the extent of damage and/or disruption expected. Flooding events are a prime example: minimising and managing the financial, human and emotional cost of floods is key for researchers, local communities, policy makers and authorities alike.

Contributing to this effort, a team of German researchers have designed a tool which harnesses our desire to share snippets of our lives via social media to support the creation of rapid inundation maps during flooding events. The research was recently published in the EGU open access journal, Natural Hazards and Earth System Sciences.

Currently, measurements of flood water heights made by river gauges, hydrodynamic-numerical models and remote sensing data – such as before and after images acquired by satellites – are used to create rapid response flood maps. Despite their successful and wide-spread use, they are not without limitations.  River gauges only allow for narrow point information on water heights during a flood and require detailed topographical data to be validated. Hydronamic-numerical models aren’t very flexible: it is difficult to build unforeseen incidents into them (e.g. a dike breach). Remote sensing techniques have limitations when it comes to providing real time information; it can take up to 48 hours for the images to be delivered and processed before they can be used.

The study authors argue that eyewitness information about flooding events shared via social media can fill in some of the gaps. Using quantitative data, such as geographical location and flood water height, held in images shared via Twitter and Flickr, can provide information to make more detailed and accurate flood maps in almost real-time. The researchers put the theory to the test for the June 2013 Dresden floods.

The city of Dresden, with its 800,000 inhabitants, sits on the banks of the River Elbe, known for its long history of flooding. This means the city’s population is more aware of the hazard and, being an urban area, likely has a large number of social media users, making it a good case study candidate.

Location of useful photos retrieved with PostDistiller and inundation depths estimates. (Photos by Denny Tumlirsch (@Flitz- patrick), @ubahnverleih, Sven Wernicke (@SvenWernicke) and Leo Käßner (@leokaesner). Taken from J. Fohringer et al. (2016))

Location of useful photos retrieved with PostDistiller and inundation depths estimates. (Photos by Denny Tumlirsch (@Flitz-patrick), @ubahnverleih, Sven Wernicke (@SvenWernicke) and Leo Käßner (@leokaesner). For instance, photos 1 and 2 show inundated roads but a dry sidewalk. This context en- ables the analyst to estimate inundation depth in the order of approximately 5 cm Taken from J. Fohringer et al. (2016))

The research team created an inundation map using only information from photos filtered from Twitter and Flickr. To collate the flood data from social media, the team designed a computer programme. In the first instance a search for key words (in both English and German) related to floods was ran: “Hochwasser”, “Flut”, “Flood”, “inundation”, to name a few. The results were then filtered by the time frame of interest (from May 5th to 21st June 2013) as well as the geolocation of the posts. This yielded a total of 84 posts from which five inundation depths were derived (see the figure caption for details of how the team achieved this), in the space of no more than four hours. The depths calculated were then used to create the inundation map.

To test the robustness of the map, the team created a second map relying only on online data acquired from the Dresden river gauge. Comparing the two maps shows that the social media created map overestimates inundation height by decimetres as well as the geographical extent of the flooding. Despite that, the study authors argue that the errors are acceptable when it comes to providing rapid inundation maps, particularly in situations when no other information is available.

Inundation maps and inundation depths derived from online water level observations (a) and social media content (b) ; inundated area derived from the reference remote sensing flood footprint (c) ; and differences between inundation depths for overlapping areas in scenarios (a) and (b) (panel d ). J. Fohringer et al. (2016))

Inundation maps and inundation depths derived from online water level observations (a) and social media content (b); inundated area derived from the reference remote sensing flood footprint (c); and differences between inundation depths for overlapping areas in scenarios (a) and (b) (panel d). J. Fohringer et al. (2016))

The case study also highlighted some of the method’s shortcomings. It will be important to improve the vertical and horizontal accuracy of the social media created maps by supplementing them with more detailed topographical terrain data. The current method of acquiring data via social media is relatively passive and relies on users sharing images from a flooding event. Crowdsourcing data, where citizens are actively encouraged to share images, would improve the reliability of the data as well as the spatial coverage.

So when you next take a selfie or capture a stunning landscape to share on social media, who knows, the data held in your images and geolocation could have even more value than you might have originally thought!

By Laura Roberts Artal, EGU Communications Officer

 

 

 References

Fohringer, J., Dransch, D., Kreibich, H., and Schröter, K.: Social media as an information source for rapid flood inundation mapping, Nat. Hazards Earth Syst. Sci., 15, 2725-2738, doi:10.5194/nhess-15-2725-2015, 2015.

Rimkus, S. et al.  A Century of UK Flood Losses (conference abstract) Geophysical Research Abstracts Vol. 18, EGU2016-11905, 2016, EGU General Assembly 2016

Trejo Rangel, M.A., et al. How Can Flood Affect the Real Estate Market? (conference abstract) Geophysical Research Abstracts, Vol. 18, EGU2016-8977, 2016, EGU General Assembly 2016

Climate-proofing the Netherlands

Emerging Leaders in Environmental and Energy Policy (ELEEP) fosters transatlantic relations, forges dialogue, and promotes leadership across energy and environmental policy landscapes. Former EGU Science Communications Fellow and ELEEP member Edvard Glücksman reports back from the Netherlands, where citizens manage the continuous threat of climate-related devastation through a combination of creatively adapted urban spaces and innovative new technologies.

In late January 1953, a storm over the North Sea wreaked havoc, causing one of the most devastating natural disasters that Northern Europe has ever seen. The surge of seawater overwhelmed coastal defences, causing extensive flooding along the Belgian, British, and Dutch coastlines.

The infamous North Sea Flood claimed roughly 2,500 lives, and damaged or destroyed tens of thousands of houses. In the Netherlands, where roughly 70% of the nation’s territory lies at or below sea level, the flood submerged over 1,300 km² of the country’s territory, destroying around 10% of agricultural land and crippling its economy.

Rotterdam is Europe’s largest and busiest port. (Credit: Edvard Glücksman)
Rotterdam is Europe’s largest and busiest port. (Credit: Edvard Glücksman)

Climate-proofing with blue solutions

The nation’s history of flooding has shaped urban design and construction initiatives across the Netherlands. This trend is particularly striking in the Dutch city of Rotterdam, which lies in a delta roughly 7 m below sea level and is vulnerable to flooding from both seawater and heavy rain. Its complex system of dikes and seawalls have a one-in-10,000 years chance of breaking, high enough for the city to take pioneering steps towards developing sustainable water management practices in preparation for the most extreme future climate scenarios.

In the offices of the Rotterdam Climate Initiative (RCI), Lissy Nijhuis, Project Manager at Rotterdam Council, depicts the city’s climate adaptation strategy as one that has recently grown to embrace ‘blue solutions’ – mitigation strategies that allow humans to protect themselves against potential catastrophic flooding events, while continuing to live with and enjoy water. 

The Watersquare Benthemplein plaza discretely weaves flood management systems into the city’s urban landscape. (Credit: Edvard Glücksman)
The Watersquare Benthemplein plaza discretely weaves flood management systems into the city’s urban landscape. (Credit: Edvard Glücksman)

According to Nijhuis, these new solutions contrast starkly with conventional approaches, which rely on separating humans from water using the most robust and resilient physical barriers available.

The blue solutions approach means that, in recent years, the RCI has adopted a long-term strategy of ‘climate-proofing’ the city by subtly adding water management infrastructure to standard urban maintenance and redevelopment activities. Nijhuis explains that this is most effectively achieved by developing first with a practical, beautiful outcome in mind, and working backwards to adjust it to particular flooding mitigation requirements.

To that end, we visited the city’s notorious Watersquare Benthemplein pilot project, a water plaza that doubles as a flood buffer during heavy rainfall, pooling water from surrounding streets and thus relieving the most immediate pressure on public drainage systems. The construction, seven years in the making and used during our visit as a basketball court by school children, is a prime example of Rotterdam’s understated but highly effective water mitigation strategy. Other similar examples – built to reduce pressure on drainage sites in times of severe flooding – include car parks that double as water storage units and the presence of absorbent green roofing on houses.

ELEEP members gather in Rotterdam’s port area. (Credit: Edvard Glücksman)
ELEEP members gather in Rotterdam’s port area. (Credit: Edvard Glücksman)

Halving emissions by 2020

Earlier this year, ELEEP visited Hamburg and witnessed first-hand the city’s commitment to transforming previously flooded and industrial areas into hubs for the development of green architecture and urban regeneration. Likewise, the Drijvend Paviljoen (Floating Pavilion) lies at the heart of Rotterdam’s mission to climate-proof itself in a sustainable manner.

Comprising three connected, floating hemispheres, anchored within the city’s old harbour, the Floating Pavilion serves as a pilot project within Rotterdam’s ambitious plan to construct a future community of floating homes. The pavilion floats on a 2.5 m-thick layer of polystyrene, which allows for construction directly on the water and is made of materials that are hundreds of times lighter than those used in conventional buildings. The roof, for example, is made of a triple-layer of foil, filled with pressurised air that insulates and keeps the building warm.

The solar-powered Floating Pavilion is a showpiece within Rotterdam Municipality’s goal of halving energy consumption and CO2 emissions in housing by 2020. It also allows stakeholders to better understand the potential challenges involved in drastically altering the city’s urban landscape, including for example how to interpret the city plan when the harbour areas becomes living quarters virtually overnight.

Rotterdam’s Drijvend Paviljoen (Floating Pavilion), a pilot in climate-proofing infrastructure. (Credit: Edvard Glücksman)
Rotterdam’s Drijvend Paviljoen (Floating Pavilion), a pilot in climate-proofing infrastructure. (Credit: Edvard Glücksman)

Rotterdam’s port is by far the city’s most prominent industrial feature. Europe’s largest and busiest port, it covers an area of 5,299 hectares and shifts nearly 12 million cargo containers per year. It also hugely impacts Europe’s energy landscape, serving as the northwestern European hub for the arrival, production, and distribution of conventional and renewable energy. The port, which has a capacity of nearly 7,000 megawatts, powers nearly a quarter of the industry and homes in the Netherlands. At the same time, twice as much electricity will be generated by other power plants in northwestern Europe as a result of coal, biomass, and natural gas imported via Rotterdam.

In a broad-ranging talk, Ruud Melieste, an economist within the Corporate Strategy Department at the Port of Rotterdam, explains the pressures faced by the port as it strives to improve sustainability credentials. Important, he explains, is the global complexity within which EU energy issues must be understood, and the pressures faced by power, chemical, and refining industries as cheaper alternatives, such as US shale gas, are found elsewhere.

In response, Melieste offers three potential future scenarios for Rotterdam and the rest of northwestern Europe. The first, known as the ‘power’ scenario, focuses on maintaining the domination of fossil fuels through large-scale, centralised energy generation. In this scenario, big countries and companies determine future events. A second option is the ‘fusion’ scenario, which focuses on maintaining a diverse portfolio of stakeholders and solutions, and aims to gradually alter the economy towards sustainable energy use, while using shale gas as a transition fuel. The third, ‘unlimited’, scenario is based on radical innovations and the acknowledgement that climate change is a truly pressing problem. Here, the transition to renewables is seen as an economic opportunity, driven by decentralised energy systems. The Port of Rotterdam is prepared, according to Melieste, for the possibility that any of these three scenarios could play out. The one most likely to emerge, however, remains unknown.

Ruud Melieste, economist for the Port of Rotterdam, explains the dimensions of Europe’s busiest port. (Credit: Edvard Glücksman)
Ruud Melieste, economist for the Port of Rotterdam, explains the dimensions of Europe’s busiest port. (Credit: Edvard Glücksman)

Although the basic idea behind Dutch climate protection strategies has persisted for over half a decade, the sites we visited in Rotterdam demonstrate that the city’s climate adaptation portfolio is slowly changing from a “dry feet at all costs” approach to one of integrative water management, where the duties associated with climate protection and the pleasures of urban space can more freely mix. The city and its port are central features in the supply of energy, water, and food to much of northern Europe. As a result, its pioneering climate-proofing efforts are in future likely to affect millions of European citizens, ensuring that extreme weather events, such as the storm of 1953, can be mitigated in the most sustainable and least invasive way possible.

By Edvard Glücksman, Associate Research Fellow, Environment and Sustainability Institute, University of Exeter

ELEEP is a collaborative venture between two non-partisan think tanks, the Atlantic Council and Ecologic Institute, seeking to develop innovative transatlantic policy partnerships. Funding was initially acquired from the European Union’s I-CITE Project and subsequently from the European Union and the Robert Bosch Stiftung. ELEEP has no policy agenda and no political affiliation. Edvard’s current project is funded by the European Social Fund.

Call for abstracts: The 9th Alexander von Humboldt Conference

The Alexander von Humboldt Conference is part of the EGU’s Topical Conference Series, and will be taking place in Istanbul, Turkey (24 – 28 March 2014). The aim of the meeting is to open a forum on natural hazard events that have a high impact and a large destructive potential, focussing on the Euro-Mediterranean Region in particular.

The theme for the conference can be broken down into nine broad areas:

  • Physical and Probabilistic Approaches to Earthquakes
  • Physics and Characterisation of Tsunamis
  • Monitoring and Risk of Volcanic Hazards
  • Hydro-Meteorological Hazards
  • Other High Impact Mediterranean Hazards (e.g., asteroid impacts, wildfires, terrigenous and submarine landslides, flooding, storm surges)
  • Complexity Analysis Approaches to Natural Hazards
  • Loss Models and Risk Assessment for Natural Catastrophes
  • What constitutes a prediction, what does not? Good Practice when Proposing Predictions of Natural Hazards
  • Communications and Education of Natural Hazard Knowledge  in the Mediterranean Region to Policy Makers, Students and the Public

In addition to the broad scientific topics, the conference will address risk assessment, communicating with the public and policymakers, and what is appropriate good practice when proposing natural hazard “predictions”.

You can submit your abstract to any one of the topics listed above until 31 January 2014. You can  register for the conference here.

Looking out over the Bosphorus from the conference location – great science and a great view! (Credit: Ali Ozgun Konca)

Looking out over the Bosphorus from the conference location – great science and a great view! (Credit: Ali Ozgun Konca)

To find out more about the 9th Alexander von Humboldt Conference: High Impact Natural Hazards Related to the Euro-Mediterranean Region, please see the conference website.

Update (07/01/13): Abstract submission and registration deadline extended to 31 January 2014.