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Posts tagged with "natural hazards"

Mangrove Planting in Senegal

Wednesday, 11. November 2009, 16:40:58

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In between I am also a bird watcher. As such I am fond of mangroves, and I have visited the mangrove areas in Senegal several times, mainly Sine-Saloum (usually staying in Toubacouta) and also once in Casamance (not always safe!).


Blue marker at Toubacouta in the Sine-Saloum delta and red marker near Kafountine in Casamance, where I took the photo below of pelicans some years ago.

In the Toubacouta I have witnessed how the mangrove forest is shrinking.

The Saloum delta region is under threat from coastal erosion and from the salinity of the soil. The mangrove forest is vital to this area; it prevents the soil from being washed away, supplies the essential nutrients for young fish and shelters the oyster colonies. The mangrove tree also provides a stock of medicinal plants used by locals and a significant source of income for the women who farm the shellfish. However, ever lower rainfall levels and chaotic exploitation of the forests have accelerated the decline of the tree population, with the resulting deterioration of the environment and dwindling resources.

I am therefor happy to see that a Senegalese environmental NGO has now announced that it had planted 34 million mangrove trees in three months in a project largely financed by French dairy giant Danone to offset its carbon footprint. According to the environmental organisation, Oceanium, some 34 million mangrove seedlings were planted between August and November 2009, 27 million in Senegal's southern Casamance region and 7 million in the Saloum river delta. Over 78,000 volunteers from 323 villages participated in the massive planting campaign. Without the mangrove forests the water becomes too salty to grow rice, a staple food for the Senegalese, fish die and the soil becomes exhausted.







Academics


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Too much rain, too soon, in Somalia

Saturday, 31. October 2009, 10:49:46

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Previously, the area around El-Waq had been suffering from drought. Flash floods caused by four days of torrential rains have now displaced more than 15,000 people in the south-western Somalian town of El-Waq near the Kenyan border and submerged most homes and businesses. A lot of livestock (weakened by the drought) have died due to the ongoing rains. El-Waq, like the rest of Somalia, was waiting for the rain but it was too much in too short a time.





Academics

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Problematic Methane Mining in Lake Kivu

Wednesday, 16. September 2009, 08:22:30

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In a post two years ago I featured methane in Lake Kivu.

Lake Kivu contains approximately 55 km3 of dissolved methane gas at a depth of 300 m. Previously, the methane concentration was assumed to be in steady state. However, recent analysis indicates that the methane concentration has increased significantly by 15 to 20% since the 1970s’ measurements. For carbon dioxide, the observed concentration increase was on the order of 10%, but was not statistically significant. The main hypothesis for this increased production of methane is a rise of the nutrient inputs caused by the fast-growing population in the catchment of Lake Kivu. Until 2004, extraction of the gas was done on a small scale, with the extracted gas being used to run boilers at a brewery. As far as large-scale exploitation of this resource is concerned, the Rwandan government is in negotiations with a number of parties to produce methane from the lake. Extraction is said to be cost effective and simple because once the gas rich water is pumped up the dissolved gases (primarily carbon dioxide, hydrogen sulphide and methane) begin to bubble out as the water pressure gets lower. This project is expected to increase Rwanda's energy generation capability by as much as 20 times and will enable Rwanda to sell electricity to neighboring African countries.

So far so well.

Extracting valuable methane from the lake's depths might, however, trigger an outburst of gas that could wash a deadly, suffocating blanket over the 2 million people who live around Kivu's shores.

A group of biochemists warns that if unregulated extraction continues unabated, it could trigger a catastrophic outgassing of carbon dioxide - another dissolved gas abundant in the lake's depths. Such a disaster occurred at Lake Nyos in Cameroon in 1986, killing 1700 people. Kivu contains 300 times more CO2 than Nyos did.

Like Nyos, Lake Kivu is permanently stratified: a deep layer of dense water laden with CO2, methane, salt and nutrients is locked away beneath a surface layer of fresh water. Methane is generated by lake-bed bacteria that feed on a stream of dead algae sinking from the surface. The CO2 enters through volcanic seeps.

The most dangerous practice is pumping waste water into the lake's shallows. If degassed water is dumped at the surface, it sinks, mixing water and salts between the lake's layers. Enough mixing would disrupt the density stratification of the lake, and could bring huge volumes of CO2-rich water to the surface. The pressure reduction would cause the CO2 to bubble out of solution.

Another question is of course “what could happen if the methane is NOT exploited?". Indeed the Government of Rwanda is working with experts to mitigate an imminent explosion of the gases trapped under the surface of Lake Kivu that could cause a serious human catastrophe. Recent reports suggest that the huge amounts of carbon dioxide and highly combustible methane gas trapped under the surface of Lake Kivu could explode soon if not exploited, leading to disastrous effects on the surrounding population. In an interview with the Rwandan newspaper The New Times, Charles Nyirahuku, the Head of Oil and Gas Unit in the Ministry of Infrastructure and Energy, confirmed that indeed the alarm is there but the Ministry is working round the clock with experts to ensure that the fears are mitigated. "Indeed much has been said about the danger and all this time we have been discussing possible mitigating measures. We carried out a comprehensive study and found out that one way to mitigate the danger is to extract the gas. For the moment that is what we are focusing on." (He may be biased of course?)

It is in any case evident that a strict set of rules and regulations has to be followed to ensure that the whole process of extraction is secure so that no explosion is triggered - and the possibility of one is completely eliminated.





Academics




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The Monsoon Trough - and Air France

Tuesday, 2. June 2009, 16:22:47

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The Air France accident is extremely tragic. Bad weather has (so far) been mentioned as a possible cause. Although this may seem unlikely as cause, I would nevertheless like to say a few words about the zone, where the plane vanished from radar screens.

The low-pressure zone near equator is known by several names and nicknames. Here are the most used - the Intertropical Convergence Zone (ITCZ), the Intertropical Front, the Monsoon trough, and the Equatorial Convergence Zone. The zone has been called the doldrums by sailors due to the lack of horizontal air movement

The Intertropical Convergence Zone is the region that circles the Earth, near the equator (from about 5° north and 5° south), where the trade winds of the Northern and Southern Hemispheres come together. The intense sun and warm water of the equator heats the air in the ITCZ, raising its humidity and causing it to rise. As the air rises it cools, releasing the accumulated moisture in an almost perpetual series of thunderstorms.

The name “trade winds” derives from the Middle English 'trade', meaning "path" or "track," and thus the phrase "the wind blows trade," that is to say, on track.

The location of the ITCZ varies with the seasons throughout the year and while it remains near the equator, the ITCZ over land ventures farther north or south than the ITCZ over the oceans due to the variation in land temperatures. The location of the ITCZ can vary as much as 40° to 45° of latitude north or south of the equator based on the pattern of land and ocean.


Variation in the location of the ITCZ drastically affects rainfall in many equatorial nations, resulting in the wet and dry seasons of the tropics rather than the cold and warm seasons of higher latitudes.

The equatorial thunderstorms may occur so high up in the atmosphere that a plane cannot just fly over it - one of the ways often used to avoid them. The storm tops, where the Air France plane had to pass, were likely near or over 15,000 meters (15 km).

• http://www.terradaily.com/reports/Missing_jet_crossed_notorious_storm_patch_meteorologist_999.html
• http://www.google.com/hostednews/ap/article/ALeqM5hTV85VtGDPV8EuRfpizHsbX2VgtQD98IKDU00

In Danish:
• http://www.dr.dk/Nyheder/Udland/2009/06/02/145532.htm?rss=true


PS: Please note that thunderstorms and hurricanes are not synonyms! This has nothing to do with the coming hurricane season. Although you get thunderstorms, when a hurricane passes, most thunderstorms occur elsewhere. It is sad to see that some people (even on the internet) don’t know that.

Apart from that my sincere condolences to the families of all those on board, and sorry for writing about something else ...


Academics



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Puntland Drought

Friday, 8. May 2009, 11:53:34

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In my post on Somalia is Burning - and We Have no Water I mentioned that the harbour Eyl in Puntland is seen as the Somali pirate capital. I also mentioned the harsh desert and the continuous drought as one among other possible reasons (including civil war) for todays piracy. The humaitarian situation is not getting any better.


Puntland was declared an autonomous state in 1998. A third of the Somali people live in Puntland.


Puntland is on the brink of a humanitarian crisis following poor rains that have created severe water and food shortages. Puntland has experienced a third consecutive seasonal rainfall failure. Most of the population relies on livestock, but poor rainfall has left them struggling to make ends meet. In some places 30 to 40 percent of the livestock has died, and what little livestock is left is so weak it cannot even be sold, and much less used for milk and meat.

Seen the humanitarian situation it does not come as a surprise that many people try to flee from the country. According to the UN Refugee Agency (UNHCR) the number of those who crossed to Yemen in 2008 was 50,000, of whom more than 1,000 people died during the journey. Apart from piracy there is therefore also money to earn from smuggling fugitives out of the country. Smugglers are reportedly charging each migrant US$100 for the trip to Yemen, but sometimes the smugglers do not even take them anywhere near Yemen. They take them on their boat, wander around the Somali coast for a night and dump them near a Somali town telling them it is Yemen.

• http://www.irinnews.org/report.aspx?ReportId=84248
• http://www.unhcr.org/refworld/docid/49f969be1b.html



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Floods in Somaliland

Monday, 20. April 2009, 18:51:20

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I had just started on a longer post on Somalia in view of the recent piracy and hostage taking problems and in view of the coming International conference on Somalia next week (23 April 2009) in Brussels. Ironically enough my RSS News Reader for unknown reasons came up with a three week old article on Floods in Somaliland. Ironical because I was going to stress the arid nature of Somalia.

First of all I think it is a bit of an illusion to talk about Somalia. There is no such country in any normal sense, but I will come back to that in my later post. For the time being I bring a map of some of the major more or less independent/autonomous parts of what we call Somalia.

Next I think it is obvious from all the TV-pictures we see from the area that most of it is desert or extremely arid. Only the region south and west of Mogadishu (Jubaland in particular) is not characterised as arid. I will also come back to that in my later post. But as you can see from my map with arid regions in yellow, all of Somaliland is characterised as arid (with a strip of desert along the coast of the Gulf of Aden).

The climate is hot, with hardly any rain at all - from April to September in fact unendurably hot. With the southwest monsoon in June–September, and the northeast monsoon in December–March you might expect two rainy seasons, but they are very irregular and as the wind often blows parallel to the Indian Ocean coast rain is not always guaranteed.

Three weeks ago however dozens of families were displaced, two people and 5,700 animals (livestock) were killed in three days after torrential rain induced flash floods in western Somaliland - around the Wajale river, which is only seasonal. The floods came days after Somaliland officials said the east of the region remained drought-stricken.

As I said I am working on a longer post on Somalia, so you may see this as a starter or maybe rather as appetiser or aperitif - now that I am talking about fluids, with the hot main course still to come.


• http://www.irinnews.org/report.aspx?ReportId=83775
• http://allafrica.com/stories/200904030641.html
• http://news.sg.msn.com/business/article.aspx?cp-documentid=3171278



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Mangroves Save Lives

Friday, 17. April 2009, 07:45:16

The 1999 Orissa cyclone - a super cyclone that hit the eastern coast of India at the end of October 1999 killed nearly 10,000 people, more than 70% of whom drowned in its surge. A new extensive study published in the Proceedings of the National Academy of Sciences (PNAS) finds that villages shielded from the storm surge by mangrove forests experienced significantly fewer deaths than villages that were less protected.

By analyzing the deaths in 409 villages in Orissa, the Indian state just north of the cyclone’s landfall, researchers showed that there would have been almost two additional deaths per village had there been no mangroves shielding the coastline from the storm surge.

In Orissa’s rural Kendrapada District, where the villages were located, the average width of mangroves has shrunk from 5.1 km in 1944 to 1.2 km today, largely because land was cleared for rice production.

Mangroves also provide many other environmental benefits, such as acting as nurseries for economically and environmentally vital fisheries, or sites for ecotourism.

Reference:
Das, S. et al. 2009
Mangroves Save Lives In Storms
Proceedings of the National Academy of Sciences
DOI: 10.1073pnas.0810440106

• http://www.redorbit.com/news/science/1671128/mangroves_save_lives_in_storms/index.html?source=r_science
• http://www.physorg.com/news158947478.html
• http://journalwatch.conservationmagazine.org/2009/04/16/life-savers/



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L'Aquila Earthquake - Followup

Tuesday, 7. April 2009, 13:59:49

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At a press conference in L'Aquila today (7 April 2009) the Italian Premier Silvio Berlusconi said 207 people were confirmed dead, while 15 people were still missing, after the earthquake that hit the city of L'Aquila. Berlusconi said slightly more than 1,000 people were wounded following the quake and that 150 had been found alive. Other media now speak about 1,500 injured and some 17,000 homeless after Monday's quake.

There has been a lot of fuss about a so-called prediction of the quake. I would like to remind you what earthquake prediction is about. An earthquake prediction is a prediction that an earthquake in a specific magnitude range will occur at a specific place at a specific time. As Amphibol (in German) rightly reminds us, an earthquake was predicted to occur at Sulmora about 30 km from L’Aquila on Sunday 29 March - but it didn’t! A week later, however, on Monday 6 April an earthquake did occur, but at L’Aquila. What would have happened if the inhabitants of Sulmora had been evacuated or had fled to L’Aquila for shelter. Just think about it - and let’s face it, so far measurements of radon emissions are more or less worthless as earthquake prediction tool for all the other reasons we have heard the last couple of days.

In my post yesterday I mentioned that the quake occurred at a normal fault. When continents (like Africa and Europe) collide you would normally expect compression of the crust, but normal faulting is an expression of extension. I didn’t go into this apparent paradox, and I no longer need to as Kim Hannula at All of My Faults Are Stress Related did that extremely well in her post here.

Finally a satellite image of central Italy that shows the rugged topography in the vicinity of L’Aquila.


Lower elevations are shown in green, while higher elevations are light brown and off-white. The steepness of the mountain slopes is indicated by shading: darker shading means steeper slopes. L’Aquila is nestled in the central Apennine Mountains, which run the length of Italy like a spine. The mountains are crisscrossed by dozens of faults. Faults are not always visible at the surface, but in this part of the Apennines, many of them are revealed by steeply sloped fault scarps. A major fault system is revealed by a scarp running north-northwest from the Focino Plain nearly to L’Aquila, passing along the eastern foothills of Mt. Velino and Mt. Ocre. L’Aquila is wedged between a pair of parallel faults running toward the northwest and a long, broken fault extending toward the east.



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Italian earthquake

Monday, 6. April 2009, 15:14:11

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An earthquake hit L'Aquila at 3.32 am local time today, 6 April 2009, killing at least 150 people and leaving up to 50,000 homeless. Preliminary estimates suggest between 10,000 and 15,000 buildings have been destroyed or damaged beyond repair in the region. It is however much to early for a final balance. The village of Onna was competely razed to the ground. It was was the country's deadliest since the Irpinia quake in the south in November 1980, which killed more than 2,500 people.

According to USGS the epicentre was at 42.423°N, 13.395°E. The depth was only about 10 km. Shallow earthquakes are usually the most damaging.

Carved up by two major fault lines, Italy has gained a reputation as one of the most earthquake prone countries in Europe. The Eurasian and African plates meet along a line which runs through North Africa and crosses the Mediterranean near southern Italy and Greece. Africa is moving northward at about 2 cm a year. As a result two main cracks - or fault lines - cut across the Italian peninsula, one running north-south along the spine of the Apennine mountains (where Aquila is situated) and another crossing east-west south of Rome and north of Naples. The city of L’Aquila (founded in 1245) is thus located in a tectonic basin bounded to the north by a northwest–southeast-trending active normal fault. (The earthquake was in fact a shallow normal-faulting event). The city sits in a valley in the central Apennines north of Rome and is built on a basin of sediments which has attracted geological interest in the past. It was hit by earthquakes repeatedly in its history including one in 1703 which flattened the centre.

Here are a few links to the first media reports from the disaster.

• http://news.bbc.co.uk/2/hi/europe/7985958.stm
• http://news.bbc.co.uk/2/hi/europe/7984867.stm
• http://www.gdacs.org/reports.asp?eventType=EQ&ID=54774&system=asgard&location=ITA&alertlevel=Green&glide_no=
• http://www.terradaily.com/reports/Strong_6.7_magnitude_quake_strikes_Italy_Rome_fire_service_999.html
• http://www.latimes.com/news/nationworld/world/la-fg-italy-quake7-2009apr07,0,1185599.story
• http://www.telegraph.co.uk/news/worldnews/europe/italy/5114636/LAquila-earthquake-damaged-ancient-baths-in-Rome.html
• http://www.telegraph.co.uk/news/worldnews/europe/italy/5114139/Italian-earthquake-experts-warnings-were-dismissed-as-scaremongering.html

In Danish:
• http://www.dr.dk/Nyheder/Udland/2009/04/06/110312.htm?nyhedsbrev
• http://ing.dk/artikel/97716-usaedvanlig-forklaring-bag-jordskaelv-mikroplader-blev-revet-fra-hinanden

In Dutch
• http://www.knack.be/nieuws/europa/aardbeving-in-italie--zeker-40-doden/site72-section25-article31778.html

In German:
• http://www.zeit.de/online/2009/15/bg-erdbeben

And a few links to fellow bloggers’ posts so far about the event:

* http://amphibol.blogspot.com/2009/04/erdbeben-in-italien.html
* http://ontario-geofish.blogspot.com/2009/04/large-earthquake-hits-italy.html
* http://daveslandslideblog.blogspot.com/2009/04/first-take-on-italy-earthquake.html
* http://geology.about.com/b/2009/04/06/italy-struck-by-m-63-quake.htm
* http://www.goodschist.com/2009/04/06/manitude-63-earthquake-in-laquila-italy/
* http://seismo.berkeley.edu/blogs/seismoblog.php/2009/04/06/title-2
* http://aldopiombino.blogspot.com/2009/04/il-terremoto-dellaquila-tra-annunci.html

more will no doubt follow.



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Zambezi Flood

Monday, 30. March 2009, 10:02:56

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The flooding along the upper Zambezi river and its tributaries is the worst since 1969. Flooding in the upper Zambezi river basin has already displaced hundreds of thousands in Angola, Namibia and Zambia. Zambia's air force began airlifting relief supplies on Friday 27 march. Namibia has declared a state of emergency. At least 100 people have died. Crocodiles and hippos are swimming through the flood waters, attacking and killing people. Field after field of crops have been destroyed, as have houses, schools, health centres and roads. More than 20 000 families have been displaced.


The waters of the Okavango delta in Botswana have reached their highest levels since 1939.

In Angola the flooding has affected more than 200 000 people . So far at least 20 people are dead.

The north of the Zambezi basin has mean annual rainfall of 1100 to 1400 mm which declines towards the south, reaching about half that figure in the south-west. The rain falls in a 4 to 6 month rainy season when the Inter-Tropical Convergence Zone moves over the basin from the north. The Inter-Tropical Convergence Zone, or ITCZ, is a region that circles the Earth, near the equator, where the trade winds of the Northern and Southern Hemispheres come together. The intense sun and warm water of the equator heats the air in the ITCZ, raising its humidity and causing it to rise. As the air rises it cools, releasing the accumulated moisture in an almost perpetual series of thunderstorms.

• http://www.terradaily.com/reports/Rain-soaked_southern_Africa_hit_by_worst_floods_in_years_999.html
• http://www.reuters.com/article/unitedNations/idUSLR643933

PS of 31 March 2009:
There are now new satellite images and more information at NASA's Earth Observatory.



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