GeoLog

Natural Hazards

GeoTalk: Severe soil erosion events and how to predict them

GeoTalk: Severe soil erosion events and how to predict them

Geotalk is a regular feature highlighting early career researchers and their work. In this interview we speak to Matthias Vanmaercke, an associate professor at the University of Liège in Belgium who studies soil erosion and land degradation across Europe and Africa. At the EGU General Assembly he received the 2018 Soil System Sciences Division Outstanding Early Career Scientists Award.

Thanks for talking to us today! Could you introduce yourself and tell us about your career path so far?

Hi! So I am Matthias Vanmaercke. I’m from Belgium. I’m studied physical geography at the University of Leuven in Belgium, where I also completed my PhD, which focused on the spatial patterns of soil erosion and sediment yield in Europe. After my PhD, I continued working on these topics but with a stronger emphasis on Africa. Since November 2016, I became an associate professor at the University of Liege, Department of Geography where I continue this line of research and teach several courses in geography.

At the 2018 General Assembly, you received a Division Outstanding Early Career Scientists Award for your contributions towards understanding soil erosion and catchment sediment export (or the amount of eroded soil material that gets effectively transported by a river system).

Could you give us a quick explanation of these processes and how they impact our environment and communities?

We have known for a long time that soil erosion and catchment sediment export pose important challenges to societies. In general, our soils provide many important ecosystem services, including food production via agriculture. However, in many cases, soil erosion threatens the long term sustainabilty of these services.

Several erosion processes, such as gully erosion, often have more direct impacts as well. These include damage to infrastructure and increased problems with flooding. Gullies can also greatly contribute to the sediment loads of rivers by directly providing sediments and also by increasing the connectivity between eroding hill slopes and the river network. These high sediment loads are in fact the off-site impacts of soil erosion and often cause problems as well, including deteriorated water quality and the sedimentation of reservoirs (contributing to lower freshwater availability in many regions).

Matthias Vanmaercke, recipient of the 2018 Soil System Sciences Division Outstanding Early Career Scientists Award. Credti: Matthias Vanmaercke.

What recent advances have we made in predicting these kinds of processes?

Given that we live in an increasingly globalised and rapidly changing world, there is a great need for models and tools that can predict soil erosion and sediment export as our land use and climate changes.

However, currently our ability to predict these processes, foresee their impacts and develop catchment management and land use strategies remains limited. This is particularly so at regional and continental scales and especially in Africa. For some time, we have been able to simulate processes like sheet and rill erosion fairly well. However, other processes like gully erosion, landsliding and riverbank erosion, remain much more difficult to simulate.

Nonetheless, the situation is clearly improving. For example, with respect to gully erosion, we already know the key factors and mechanisms that drive this process. The rise of new datasets and techniques helps to translate these insights into models that will likely be able to simulate these processes reasonably well. I expect that this will become feasible during the coming years.

 

What is the benefit of being able to predict these processes? What can communities do with this information?

These kinds of predictions are relevant in many ways. Overall, soil erosion is strongly driven by our land use. However, some areas are much more sensitive than others (e.g. steep slopes, very erodible soil types). Moreover, many of these different erosion processes can interact with each other. For example, in some cases gully formation can entrain landslides and vice versa.

Models that are capable of predicting these different erosion processes and interactions can strongly help us in avoiding erosion, as they provide information that is useful for planning our land use better. For instance, these models can help determine which areas are best reforested or where soil and water conservation measures are needed.

They also help with avoiding and mitigating the impacts of erosion. Many of these processes are important natural hazards (e.g. landsliding) or are strongly linked to them (e.g. floods). Models that can better predict these hazards contribute to the preparedness and resilience of societies. This is especially relevant in the light of climate change.

However, there are also impacts on the long-term. For example, many reservoirs that were constructed for irrigation, hydropower production or other purposes fill up quickly because eroded sediments that are transported by the river become deposited behind the dam. Sediment export models are essential for predicting at what rate these reservoirs may lose capacity and for designing them in the most appropriate ways.

At the Assembly you also gave a presentation on the Prevention and Mitigation of Urban Gullies Project (PREMITURG-project). Could you tell us a bit more about this initiative and its importance?

Urban mega-gullies are a growing concern in many tropical cities of the Global South. These urban gullies are typically several metres wide and deep and can reach lengths of more than one kilometre. They typically arise from a combination of intense rainfall, erosion-prone conditions, inappropriate city infrastructure and lack of urban planning and are often formed in a matter of hours due to the concentration of rainfall runoff.

Urban gully in Mbuji-Maji, Democratic Republic of Congo, September 2008. Credit: Matthias Vanmaercke

Given their nature and location in densely populated areas, they often claim casualties, cause large damage to houses and infrastructure, and impede the development of many (peri-)urban areas.  These problems directly affect the livelihood of likely millions of people in several countries, such as the Democratic Republic of Congo, Nigeria, and Angola. Due to the rapid growth of many cities in these countries and, potentially, more intensive rainfall, this problem is likely to aggravate in the following decades.

With the ARES-PRD project PREMITURG, we aim to contribute to the prevention and mitigation of urban gullies by better studying this problem. In close collaboration with the University of Kinshasa in the Democratic Republic of Congo (DRC) and several other partners and institutes, we will study this underestimated geomorphic hazard across several cities in DRC. With this, we hope to provide tools that can predict which areas are the most susceptible to urban gullying so that this can be taken into account in urban planning efforts. Likewise, we hope to come up with useful recommendations on which techniques to use in order to prevent or stabilise these gullies. Finally, we also aim to better understand the societal and governance context of urban gullies, as this is crucial for their effective prevention and mitigation.

Interview by Olivia Trani, EGU Communications Officer

June GeoRoundUp: the best of the Earth sciences from around the web

June GeoRoundUp: the best of the Earth sciences from around the web

Drawing inspiration from popular stories on our social media channels, as well as unique and quirky research news, this monthly column aims to bring you the best of the Earth and planetary sciences from around the web. 

Major story  

While May’s headlines may have been dominated by the Kilauea Volcano’s recent eruption in Hawaii, the science news world directed its attention to another volcanic event early this month. On June 3, Guatemala’s Volcán de Fuego erupted, sending plumes of volcanic ash several kilometres into the air. The volcano also unleashed an avalanche of hot gas and debris, otherwise known as pyroclastic flows, more than 10 kilometres down the volcano’s flanks onto the surrounding valley.

The Volcán de Fuego has been an active volcano since 2002, however, this latest event has been the volcano’s most violent eruption in more than four decades.

By 23 June, officials reported that the eruption has killed 110 people from surrounding villages, with hundreds more missing or injured.

Both Kilauea and Fuego gained international attention this year, but the two volcanoes exhibit very different behaviours by nature.

Kilauea is a shield volcano, with a relatively gradual slope and a highly fluid lava flow that can travel far distances compared to other volcanic archetypes. While the volcanic eruption’s lava, ash and haze present real threats to nearby communities, very few injuries have been reported.

“Lava flows rarely kill people,” said Paul Segall, a professor of geophysics at Stanford University, to the New York Times. “They typically move slow enough that you can walk out of the way.”

The Fuego volcano on the other hand is a stratovolcano, characterised by a cone-shaped peak built by layers of lava and ash. This type of volcano usually contains more viscous magma, meaning the hot liquid material has a sticky, thicker consistency. This type of fluid in volcanoes “clogs their plumbing and leads to dramatic explosions,” says Smithsonian Magazine.

Stratovolcanoes like Fuego also often release pyroclastic flows. These plumes can be a major threat to human health and make this kind of volcano particularly dangerous. “On its surface, a pyroclastic flow looks like a falling cloud of ash. But if you could peer into the cloud, you would find a really hot and fast-moving storm of solid rock,” reported PBS NewsHour.

Paul Rincon, a science editor for BBC News notes that pyroclastic flows can reach speeds of up to 700 kilometres per hour and are extremely hot, with temperatures between 200 to 700 degrees Celsius.

As of June 17, Guatemalan authorities have officially stopped looking for bodies and survivors. However, some local rescue workers have kept on with their search. 

What you might have missed

Meanwhile this month, in a vastly different part of the world, scientists have uncovered a wealth of new insight into Antarctica and how the region’s ice melts. Some of the discoveries made known are very foreboding while others more uplifting.

Let’s start with the bad news first. A study published this month in Nature revealed that Antarctica is melting faster than ever, and the continent’s rate of ice loss is only accelerating.

The report explains that before 2012 the Antarctic ice sheet steadily lost 76 billion tonnes of ice each year, contributing 0.2 milimetres to sea-level rise annually. However, since then, Antarctica’s rate of ice loss has increased threefold. For the last fives years the ice sheet has shed off 219 billions tonnes of ice each year. This ice loss now corresponds to a 0.6 milimetre contribution, making Antarctica one of the biggest sources of sea-level rise.

The largest iceberg ever recorded broke away from the Antarctic Peninsula in 2017. Pictured here is the iceberg’s western edge. (Credit Nathan Kurtz/NASA)

This record pace could have a devastating impact around the world, the researchers involved with the study say.

“The continent is now melting so fast, scientists say, that it will contribute six inches (15 centimeters) to sea-level rise by 2100,” reports the New York Times.

The articles continues: “’around Brooklyn you get flooding once a year or so, but if you raise sea level by 15 centimeters then that’s going to happen 20 times a year,’ said Andrew Shepherd, a professor of earth observation at the University of Leeds and the lead author of the study.”

On the other hand, one study published this month in Science offers a glimmer of hope, suggesting that a natural geologic process may help counteract some of the Earth’s sea level rise.

A team of researchers found evidence that, in response to losing ice mass, the ground underneath melting ice sheets naturally lifts up, and more substantially than scientists had previously believed. This process could help prevent further ice loss by land locking vulnerable ice sheets.

Scientists say that many ice sheets in the West Antarctic are at risk of collapsing, and furthermore contributing to sea level rise, because they are in direct contact with the ocean. The relatively warm seawater can melt these glaciers from underneath, making these giant frozen masses more at risk of losing a substantial amount of ice.

However, the new research on the West Antarctic Ice Sheet finds that as these ice masses lose weight, the ground underneath springs up, acting much like a memory-foam mattress.

“This adjustment of the land once the weight of the ice has been lifted is known as ‘glacial isostatic adjustment,’” says Carbon Brief. “It is usually thought to be a slow process, but the new data suggests the ground uplift beneath the [Amundsen Sea Embayment] area is occurring at an unprecedented rate of 41mm per year.”

A press release from Delft University of Technology in the Netherlands goes on to say that “the measured uplift rate is up to 4 times larger than expected based on the current ice melting rates.”

While this discovery offers a brighter view to the serious state of Earth’s melting ice, scientists still caution that this natural grounding process may be rendered useless in extreme cases climate change with extensive ice loss.

Links we liked 

The EGU story

For the first time, we gave participants at the annual EGU General Assembly the opportunity to offset the COemissions resulting from their travel to and from Vienna.

We are happy to report that, as a result of this initiative, we raised nearly 17,000 EUR for a carbon offsetting scheme. The Carbon Footprint project the EGU is donating to aims to reduce deforestation in Brazil and “is expected to avoid over 22 million tonnes of carbon dioxide equivalent greenhouse gas emissions over a 40 year period.”

Do you enjoy the EGU’s annual General Assembly but wish you could play a more active role in shaping the scientific programme? Now is your chance! Help shape the scientific programme of EGU 2019.

From now until 6 Sep 2018, you can suggest:

  • Sessions (with conveners and description),
  • Short Courses, or;
  • Modifications to the existing skeleton programme sessions

Plus from now until 18 January 2019, you can propose townhall meetings. It’s important to note that, for this year’s General Assembly, session proposals for Union Symposia and Great Debates are due by 15 August 2018

And don’t forget! To stay abreast of all the EGU’s events and activities, from highlighting papers published in our open access journals to providing news relating to EGU’s scientific divisions and meetings, including the General Assembly, subscribe to receive our monthly newsletter.

Geosciences Column: Landslide risk in a changing climate, and what that means for Europe’s roads

Geosciences Column: Landslide risk in a changing climate, and what that means for Europe’s roads

If your morning commute is already frustrating, get ready to buckle up. Our climate is changing, and that may increasingly affect some of central Europe’s major roads and railways, according to new research published in the EGU’s open access journal Natural Hazards and Earth System Sciences. The study found that, in the face of climate change, landslide-inducing rainfall events will increase in frequency over the century, putting central Europe’s transport infrastructure more at risk.  

How do landslides affect us?

Landslides that block off transportation corridors present many direct and indirect issues. Not only can these disruptions cause injuries and heavy delays, but in broader terms, they can negatively affect a region’s economic wellbeing.

One study for instance, published in Procedia Engineering in 2016, examined the economic impact of four landslides on Scotland’s road network and estimated that the direct cost of the hazards was between £400,000 and £1,700,000. Furthermore the study concluded that the consequential cost of the landslides was around £180,000 to £1,400,000.

Such landslides can have a societal impact on European communities as well, as disruptions to road and railway networks can impact access to daily goods, community services, and healthcare, the authors of the EGU study explain.

Modelling climate risk

To analyse climate patterns and how they might affect hazard risk in central Europe, the researchers first ran a set of global climate models, simulations that predict how the climate system will respond to different greenhouse gas emission scenarios. Specifically, the scientists ran climate projections based on the Intergovernmental Panel on Climate Change’s A1B socio-economic pathway, a scenario defined by rapid economic growth, technological advances, reduced cultural and economic inequality, a population peak by 2050, and a balanced reliance on different energy sources.

They then determined how often the conditions in their climate projections would trigger landslide events specifically in central Europe using a climate index that estimates landslide potential from the duration and intensity of rainfall events. The index, established by Fausto Guzzetti of National Research Council of Italy and his colleagues, suggests that landslide activity most likely occurs when a rainfall event satisfies the following three conditions: the event lasts more than three days, total downpour is more than 37.3 mm and at least one day of the rainfall period experiences more than 25.6 mm.

The researchers also incorporated into their models data on central Europe’s road infrastructure as well as the region’s geology, including topography, sensitivity to erosion, soil properties and land cover.

Overview of a particularly risk-prone region along the lowlands of Alsace and the Black Forest mountain range: (a) location of the region in central Europe and median of the increase in landslide-triggering climate events for (b) the near future and (c) the remote future.

The fate of Europe’s roadways

The results of the researchers’ models suggest that the number of landslide-triggering rainfall events will increase from now up until 2100. Their simulations also find while that these hazardous rainfall events slightly increase in frequency between 2021 and 2050, the number of these occurrences will be more significant between 2050 and 2100.  

While the flat, low-altitude areas of central Europe will only experience minor increases in landslide-inducing rainfall activity, regions with high elevation, like uplands and Alpine forests, are most at risk, their findings suggest.

The study found that many locations along the north side of the Alps in France, Germany, Austria and the Czech Republic may face up to seven additional landslide-triggering rainfall events as our climate changes. This includes the Vosges, the Black Forest, the Swabian Jura, the Bergisches Land, the Jura Mountains, the Northern Limestone Alps foothills, the Bohemian Forest, and the Austrian and Bavarian Alpine forestlands.

The researchers go on to explain that much of the Trans-European Transport Networks’ main corridors will be more exposed to landslide-inducing rainfall activity, especially the Rhine-Danube, the Scandinavian-Mediterranean, the Rhine-Alpine, the North Sea-Mediterranean, and the North Sea-Baltic corridors.

The scientists involved with the study hope that their findings will help European policy makers make informed plans and strategies when developing and maintaining the continents’ infrastructure.  

Imaggeo on Mondays: Hints of an eruption

Imaggeo on Mondays: Hints of an eruption

The photograph shows water that accumulated in a depression on the ice surface of Vatnajökull glacier in southeastern Iceland. This 700m wide and 30m deep depression [1], scientifically called an ‘ice cauldron’, is surrounded by circular crevasses on the ice surface and is located on the glacier tongue Dyngjujökull, an outlet glacier of Vatnajökull.

The photo was taken on 4 June 2016, less than 22 months after the Holuhraun eruption, which started on 29 August 2014 in the flood plain north of the Dyngjujökull glacier and this depression. The lava flow field that formed in the eruption was the largest Iceland has seen in 200 years, covering 84km2 [2] equal to the total size of Manhattan .

A number of geologic processes occurred leading up the Holuhraun eruption. For example, preceding the volcanic event, a kilometre-wide area surrounding the Bárðarbunga volcano, the source of the eruption, experienced deformation. Additionally, elevated and migrating seismicity at three to eight km beneath the glacier was observed for nearly two weeks before the eruption [3]. At the same time, seven cauldrons, like the one in this photo, were detected on the ice surface (a second water filled depression is visible in the upper right corner of the photo). They are interpreted as indicators for subglacial eruptions, since these cauldrons usually form when geothermal or volcanic activity induces ice melt at the bottom of a glacier [4].

Fracturing of the Earth’s crust led up to a small subglacial eruption at the base of the ice beneath the photographed depression on 3 September 2014. This fracturing was further suggested as the source of long-lasting ground vibrations (called volcanic tremor) [5].

My colleagues and I studied the signals that preceded and accompanied the Holuhraun eruption using GPS instruments, satellites and seismic ground vibrations recorded by an array of seismometers [2, 5]. The research was conducted through a collaboration between University College Dublin and Dublin Institute for Advanced Studies in Ireland, the Icelandic Meteorological Office and University of Iceland in Iceland, and the GeoForschungsZentrum in Germany.

The FP7-funded FutureVolc project financed the above mentioned research and further research on early-warning of eruptions and other natural hazards such as sub-glacial floods.

By Eva Eibl, researcher at the GeoForschungsZentrum

Thanks go to www.volcanoheli.is who organised this trip.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.