Coastal ecosystems for DRR and CCA: mangroves and other coastal vegetation Fabrice Renaud United Nations University Institute for Environment and Human Security Intensive Summer Course Advancing DRR to enhance sustainable development in a changing world 20 June / 1 July 2016, Bonn, Germany
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Coastal ecosystems for DRR and CCA:
mangroves and other coastal vegetation
Fabrice Renaud
United Nations University
Institute for Environment and Human Security
Intensive Summer Course
Advancing DRR to enhance sustainable development
in a changing world
20 June / 1 July 2016, Bonn, Germany
Outline
Some benefits from coastal vegetation
Case study Sri Lanka (tsunami context)
Brief Example from 2011 Great East Japan
Earthquake and Tsunami
Brief Example of Coastal Erosion in North
Central Java, Indonesia
Brief Example from salinity intrusion in the
Mekong Delta, Vietnam
Some benefits from coastal
vegetation
Protection of coastal zones
with ecological approaches
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Extension, production and losses of
vegetated coastal ecosystems
Source: Duarte et al (2013): The role of coastal plant communities for climate change mitigation and adaptation. Nature Climate Change
SOURCE: Titov et al. 2005. DOI: 10.1126/science.1114576
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Exposure: Buffering the
Populations
Following the tsunami, the fact that some ecosystem components had previously been degraded by human interventions was blamed for the damages & losses:
• Costal vegetation in general and mangroves in particular
• Sand dunes
• Sea grasses
• Coral reefs
It was assumed that these features would have protected the population by:
• Reducing the energy of the waves
• Reducing the exposure of the populations (increased distance from coastline)
Vermaat & Thampanya. Estuarine, Coastal & Shelf Sci (in press)
• Erratum Mistake in stats: mortality and
property loss were not less behind mangroves
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Some Factors at Play – but
much more Research needed
• There are many potential factors to consider incl.:
– Bathymetry
– Topography
– Distance of settlement
– Coastal vegetation
– Impact angle
– Distance from epicentre
• Chatenouy & Pedduzzi:
– Depth of sea floor at 10km
– Length of proximal slope
– % protection from seagrass
– Distance from fault line
– % protection from coral
Source: Chatenoux & Peduzzi. Natural Hazards. DOI 10.1007/s11069-
006-0015-9
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Source: PhD research of Marcus Kaplan (UNU-EHS)
Tsunami, Coastal Vegetation and Vulnerability
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Tsunami, Coastal Vegetation and Vulnerability
Source: PhD research of Marcus Kaplan (UNU-EHS)
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Brief Example from 2011 Great East
Japan Earthquake and Tsunami
Earthquake and Tsunami impact in
Sendai, Wakabayashi Ward, Arahama
District
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23/09/2003 17/04/2011
04/10/2011 29/03/2012
Photo Credit: Tohoku Construction Association . Do not reproduce
Coastal Forests in Sendai
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Photo Credit: Fabrice Renaud/UNU-EHS Do not reproduce
Resistance of trees
Trunk bending and breaking were closely related to tsunami water depth and hydrodynamic parameters
Tree overturning was found to be more site specific, and the root-soil strength greatly affected the critical value
Debris trapping but also secondary damage to people and buildings
Source: Tanaka et al (2012): Breaking pattern and critical breaking condition of Japanese pine trees on coastal sand dunes in huge tsunami caused by Great East Japan
Earthquake. Nat Hazards 65:423–442
Issues with engineering
solutions
Source: Tanalka et al (2012): Coastal and estuarine morphology changes induced by the 2011 Great East Japan Earthquake Tsunami. Coastal Engineering Journal 54(1): DOI:
10.1142/S0578563412500106
Ecosystem and DRR in the context
of the Great East Japan Earthquake
The Earthquake Disaster Reconstruction Plan (City of Sendai, 2011)
• Puts some emphasis on the environment
• Addresses agricultural issues
• Restore the eautiful oast
• Utilising ostal prevention forests e pli itl mentioned
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Ecosystem and DRR in the context of the
Great East Japan Earthquake
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Source: Sendai City Earthquake Disaster Reconstruction Plan (2011)
Devastation in Minamisanriku & plans
for relocation
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Brief Example of Coastal Erosion in
North Central Java, Indonesia
Coastal inundation –
Central Java
Source: Marfai (2011): Impact of costal inundation on ecology and agricultural land use. Case study in Central Java, Indonesia. Quaestiones