Tag Archives: tsunami

Mangroves: a natural form of hazard mitigation

by Caitlin Douglas

Mangroves, a type of tropical evergreen forest growing in the intertidal zones in the tropics and subtropics (32oN and 38oS), consist of tree species well adapted to the regularly changing salinity concentrations and water levels associated with such areas. Mangroves are highly productive ecosystems of high ecological importance. Ostling et al. (2009) describe mangroves and the role they play in ecological processing and natural hazards mitigation.

The special roots of mangroves allow them to anchor themselves in this ever changing environment and therefore serve to slow tidal forces and form an important natural barrier against tropical storms and tsunamis. The presence of mangroves has been shown to increase human survival during cyclones and tsunamis as well as being more effective than alternative natural or artificial barriers (i.e. other types of trees, sand dunes, seawalls, groins etc). Mangroves also provide habitat for shrimp, crocodiles and a nursery ground for fishery stock. Currently these forests are being cleared for various agricultural, forestry and urban uses, such as shrimp aquaculture which has led to the clearing of millions of hectares of mangroves. Without the mangroves, natural fishery stocks are affected which leads to more mangroves being cleared to support more extensive and varied types of aquaculture. In light of the growing realisation of the importance of mangroves, revegetation programmes are underway in Bangladesh, Thailand, Vietnam and Tanzania.

Ostling, J., Butler, D., Dixon, R. The Biogeomorphology of Mangroves and their Role in Natural Hazard Mitigation. Geography Compass, 3(5): 1607-1624

Cancún: From mangrove paradise to polluted megasprawl. The Guardian.  9 December 2010

Is the tsunami too big to beat? The Guardian. 11 March 2011

Mangroves. BBC Nature

Lessons from the past

By Paulette Cully

In an upcoming article in the Geographical Journal Chester and Chester examine the ‘Impact of eighteenth century earthquakes on the Algarve region, southern Portugal’. Using data collected in the field and archival information the authors discuss the economic and social impacts on the Algarve of the two earthquakes and their related tsunamis which took place in 1722 and 1755. Using the information gathered, the study also focuses on the lessons which have been learnt for future hazard planning in the region. 

Similarly, a recent news article marking the fiftieth anniversary this month of the largest earthquake ever recorded (magnitude 9.5), which took place in southern Chile in 1960, charts the life saving legacy that the quake left in its wake. Not only was the quake the largest ever recorded but it approached the upper limit that the planet is capable of producing in a single event. With an equivalent energy of 20,000 times the Hiroshima bomb, the quake caused the earth to wobble and sent it ringing for many days. The Chilean quake would become part of a convincing argument in support of the far-reaching plate tectonics theory and provide a textbook illustration of a subduction zone earthquake. The earthquake produced a tsunami 25 metres high which travelled across the Pacific reaching Japan 17,000  kilometres away where it killed 140 people. This spurred nations bordering the Pacific to set up an international tsunami warning system. In addition, deposits left by the tsunami have allowed geologists to develop a model which helps them identify other areas which may be prone to giant subduction zone earthquakes.

   Click here to read the full news article

  Click here to read the Chester  and Chester article

Reacting to Disaster

Indian Ocean Earthquake

By Jenny Lunn

Natural disasters are never far from the news. Over the last 24 hours, we have heard of a tsunami affecting South Pacific islands and an earthquake in Sumatra, Indonesia. We usually watch disasters unfold on our TV screens; we sometimes give some money. Mostly we feel completely helpless about a situation far away. Some people are able to respond by travelling to the disaster area to offer their professional skills as doctors, nurses, fire fighters or engineers. But what professional skills can academics bring to such situations?

Catherine Brun’s paper in the Geographical Journal looks at researchers who conducted participatory action research in Sri Lanka after the 2004 tsunami wrought devastation on the fringes of the Indian Ocean. Post-disaster research is essential for understanding how people react to disasters and cope in the aftermath. Such insights are vital for forecasting, planning and mitigating against future disasters. However, the key question is how the research can balance being practical and helpful whilst gathering useful data.

Though referring to research in the aftermath of a disaster, the issues raised by Brun are applicable to social scientists engaged in all kinds of research, as they consider the ethics and responsibility of engagement.

60% worldRead the BBC News item about the South Pacific tsunami

60% worldRead the BBC News item about the Indonesian earthquake

60% worldRead Brun (2009) A geographers’ imperative? Research and action in the aftermath of disaster in Geographical Journal