EFFECTS OF COASTAL VEGETATION SPECIES AND GROUND SLOPE ON STORM SURGE DISASTER MITIGATION
Proceedings of the 32nd International Conference
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Keywords

Rhizophora apiculata
Casuarina equisetifolia
Cyclonic storm surge

How to Cite

Das, S. C., Iimura, K., & Tanaka, N. (2011). EFFECTS OF COASTAL VEGETATION SPECIES AND GROUND SLOPE ON STORM SURGE DISASTER MITIGATION. Coastal Engineering Proceedings, 1(32), currents.24. https://doi.org/10.9753/icce.v32.currents.24

Abstract

The coastline of Bangladesh is mostly exposed to extreme meteorological and hydrological conditions where cyclones and storm surges cause devastating effects including loss of human lives and destruction of properties. Coastal vegetation has been considered as a low-cost and natural protection to reduce the energy of current and surge. Present study explored the effectiveness of coastal vegetation against cyclonic storm surge based on species composition, forest width and near-shore run-up slope revealed by field investigations and numerical simulations. A calibrated hydrodynamic numerical model based on modified one-dimensional depth-averaged non-linear long wave differential equations was used to simulate the storm surge mitigation effected by the coastal vegetation. Considering two different types of coastal species, mangrove species, Rhizophora apiculata and beach species, Casuarina equisetifolia, numerical simulations were conducted to assess the effect of coastal forest on the storm surge mitigation. This analysis showed that double layers of wide vegetation belt (300 m) in the vertical direction with R. apiculata and C. equisetifolia on mild slope (1:500) exhibited a strong potential to decrease surge wave height and velocity. However, water depth reduction was low compared with flow velocity reduction. The maximum water depth and current velocity reduced to 1.4m (22% reduction) and 1.2m/s (49% reduction), respectively, behind the vegetation in comparison with the case without vegetation. Wide coastal vegetation belt with mild slope might be suitable for storm surge energy reduction; however, a doubling or tripling of forest width (from 100 m to 200 m or 300 m) did not produce two-fold or three-fold increase of wave reduction with negligible additional velocity reduction. For the same vegetation density the wave energy reduction by R. apiculata was not increased significantly compared to the C. equisetifolia. But young densely C. equisetifolia found more effective to reduce storm surge energy. The information would be of value to policy and decision makers for coastal landscape planning, rehabilitation and coastal resource management.
https://doi.org/10.9753/icce.v32.currents.24
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References

Danielsen F., Sorensen, M.K., Olwig, M.F., Selvam, V., Parish. F., Burgess, N.D., Hiraishi, T., Karunagaran, V.M., Rasmussen, M.S., Hansen, L.B., Quarto, A., Suryadiputra, N. 2005. The Asian tsunami: a protective role for coastal vegetation, Science 320(5748), 643 pp.

Food and Agriculture Organization (FAO) of the United Nations Regional Office for Asia and the Pacific. 2007. Coastal protection in the aftermath of the Indian Ocean tsunami: What role for the forests and trees? Proceedings of the Regional Technical Workshop, Khao Lak, Thailand, 28-31 August 2006.

Harada, K., and Imamura, F. 2006. Effects of coastal forest on tsunami hazard mitigation-a preliminary investigation, In: Tsunamis: case studies and recent developments, Advances in Natural and Technological Hazards Research, Berlin, Springer, 279-292.

Hiraishi, T., and Harada, K. 2003. Greenbelt Tsunami Prevention in South-Pacific Region, Report of the Port and Airport Research Institute, 42 (2), 1-20.

Investigation Team of Japan Society of Civil Engineering. 2008. Investigation report on the storm surge disaster by cyclone Sidr2007, Bangladesh (

Kabir, M.M., Ahmed, M.M.Z., Azam, M.H., and Jakobsen, F. 2006. Effects of afforestation on strom surge propagation: a mathematical model study, Institute of water modelling (

Karim, M.F., and Mimura, N. 2008. Impact of climate change and sea-level rise on cyclonic storm surge floods in Bangladesh, Global Environmental Change, 18, 490-500.http://dx.doi.org/10.1016/j.gloenvcha.2008.05.002

Mascarenhas, A., and Jayakumar, S. 2008. An environmental perspective of the post-tsunami scenario along the coast of Tamil Nadu, India: Role of sand dunes and forests, Journal of Environmental Management, 89, 24-34. PMid:17517466 http://dx.doi.org/10.1016/j.jenvman.2007.01.053

Massel, S.R., Furakawa, K., and Brinkman, R.M. 1999. Surface wave propagation in mangrove forests. Fluid Dynamics Research, 24, 219-249.http://dx.doi.org/10.1016/S0169-5983(98)00024-0

Mazda, Y., Magi, M., Ikeda, Y., Kurokawa, T, and Asano, T. 2006. Wave reduction in a mangrove forest dominated by Sonneratia sp., Wetland Ecology and Management, 14, 365-378. http://dx.doi.org/10.1007/s11273-005-5388-0

Ministry of Transport, Japan. 1996. Prediction of storm surge in Tokyo Bay, The second district port consortium bureau, 191pp. (in Japanese).

Murty, T.D, and Neralla, V.R. 1992. On the recurvature of tropical cyclones and the storm surge problem in Bangladesh, Natural Hazards, 6, 275-279. http://dx.doi.org/10.1007/BF00129512

Nandasana, N.A.K, Tanaka, N., and Tanimoto, K. 2008. Tsunami current inundation of ground with coastal vegetation effects; an initial step towards a natural solution for tsunami amelioration, Journal of earthquake and tsunami, 2, 157-171.

Paul, B.K. 2009. Why relatively fewer people died? The case of Bangladesh's cyclone Sidr, Natural Hazards, 50, 289-304.http://dx.doi.org/10.1007/s11069-008-9340-5

Shuto, N. 1987. The effectiveness and limit of tsunami control forests. Coast Eng Jpn, 30(1), 143-153.

Tanaka, N., Sasaki, Y., Mowjood, M.I.M., Jinadasa, K.B.S.N., and Homchuen, S. 2007. Coastal vegetation structures and their functions in tsunami protection: Experience of the recent Indian Ocean tsunami, Landscape and Ecological Engineering, 3, 33-45.http://dx.doi.org/10.1007/s11355-006-0013-9

Tanaka, N., Nandasena, N.A.K., Jinadasa, K.B.S.N., Sasaki, Y., Tanimoto, K., and Mowjood, M.I.M. 2009. Developing effective vegetation bioshield for tsunami protection, Journal of Civil and Environmental Engineering Systems, 26, 163-180.http://dx.doi.org/10.1080/10286600802435850

Tanimoto, K., Tanaka, N., Nandasena, N.A.K., Iimura, K., and Shimizu T. 2007. Numerical simulation of tsunami prevention by coastal forest with several species of tropical tree (Japanese with English abstract), Annual Journal of Coastal Engineering, JSCE, 54, 1381-1385. http://dx.doi.org/10.2208/proce1989.54.1381

Thuy, N.B., Tanimoto, K., Tanaka, N., Harada K., Iimura, K. 2009. Effect of Open Gap in Coastal Forest on Tsunami Run-up - Investigations by Experiment and Numerical Simulation, Ocean Engineering, 36, 1258-1269. http://dx.doi.org/10.1016/j.oceaneng.2009.07.006

Yanagisawa, H., Koshimura, S., Goto, K., Miyagi, T., Imamura, F., Ruangrassamee, A., and Tanavud, C. 2009. The reduction effects of mangrove forest on a tsunami based on field surveys at Pakarang Cape, Thailand and numerical analysis, Estuarine, Coastal and Shelf Science, 81, 27-37.http://dx.doi.org/10.1016/j.ecss.2008.10.001

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