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Sandwip

Case study sites

Site description

Keywords: Off-shore Island, Delta

The international Case Study site of Sandwip Island is located north-eastern side of The Bay of Bengal, nearby the main port city of Chittagong. It is one of the most ancient islands of Bangladesh. As of 2001 Bangladesh census, Sandwip has a population of 292,773. The entire island is 50km long and 5 to 15km wide. It has been formed by silt deposits from the estuary of the Meghna river, thus resulting in fertile lands.

The island is located at a frequent passage of tropical cyclones and therefore extremely prone to storm induced floods and other associated natural hazards. Every year people in the Island face risks from cyclones and following storm surges threatening lives and households of the entire community. Coastal erosion is rapidly changing the living space for the community. It is also exposed to a macro-tidal regime, with tidal variation in the range of 3 to 6m from neap to spring tides. A prominent, counter- clockwise, residual circulation, which is very turbulent in nature, is present around it. The highest tidal current velocities, of up to 4m/s, are observed in the Case Study site and upper reach of the estuary during the spring tides and the rainy seasons respectively. Located in an active Delta, the morphological evolution around the Island is also very active due to the significant degree of hydrodynamic and sediment transport processes. The Meghna estuary is mostly meso-tidal, with the exception of a small locality near Sandwip which is macro-tidal. It is predominantly semidiurnal in nature, with the tidal range to vary subsequently between the spring and the neap tide. During monsoon season (high discharge period), the tidal influence diminishes significantly and it can even be completely flushed out of the estuary. During the periods from May through September, southwesterly monsoon winds predominate, with an occasional intensity of gale force (11.5–28.0m/s). Wave observations at the Sandwip Channel, off the Karnofully River mouth, showed only a moderate wave climate with a maximum wave height of 2.4m.

Why was this area selected?

The geographical position, the frequent occurrence of extreme climatological events and the socio-economic regime in Bangladesh, transforms effective Disaster Risk Reduction (DRR) measures in an extremely challenging task. Regardless the immeasurable difficulties, continuous effort for early warnings and for a community-based response framework has significantly reduced the loss of lives in the past decades. One of the biggest challenges in the region is to provide reliable and easy-to-understand warnings on coastal flooding in the district and sub-district level and thus, the work done during this project will provide the base and demonstrate the future directions towards these actions.

Land, coastal and marine uses

Keywords: Residential use, Agriculture

Sandwip Island’s population is quite large compared to its size, making traditional residential structures the main land use in the area. A significant amount of space is also devoted to the agriculture of vegetables, cereals, rise and fruit. A large number of the Island’s population is also occupied in the fisheries sector. Due to the lack of equipment and relevant infrastructure, both agriculture and fisheries are operating in a very traditional manner, which makes the community vulnerable to the recurrent coastal flooding and associated natural hazards.

Hazards

Keywords: Storm surges, Tidal inundation, Erosion, Wind, Sea level rise. Tsunamis

The most important hazards in the area are caused by tropical cyclones and associated storm surges, resulting in massive flooding, that affects the entire Island and sea area nearby. Often these phenomena are combined with other hazards, such as strong winds and tidal inundation, resulting in intensified risk. The dense population and persistent poverty of the country results in recurrent casualties of immeasurable scales.
The rate of the erosion is very high and not compensated by the deposit, despite its large rate. Several attempts to assess the erosion rate have been done but mainly led to conflicts, evidencing the particular difficulties to develop scientific studies in this site.
There are 11 potential sources of earthquakes in the Bay of Bengal and local tsunami inundation may reach up to 5m at the Sunderbans region and some regions near Hatiya and Nijhum Dwip. The Chittagong-Teknaf coastline is also in risk of probable inundation from tsunamis.

Socio-Economic losses & Environmental Impacts

Keywords: Loss of life, Loss of living space, Impact on agriculture

In the years 1825, 1876, 1985 and 1991, Sandwip was affected by extreme meteorological events causing severe marine flooding and leading to immense destruction. During the most damaging storm that affected the island, in 1991, the estimated storm surge height was 6m and the human casualties were estimated at approximately 40,000 people, when 80% of the residential infrastructures were also destroyed. More specifically 25,000 human casualties occurred during the cyclone and 15,000 human casualties were caused from malnutrition and diseases after the event. In previous extreme events the human casualties were approximately 7,000 people. These devastating losses are becoming even more severe due to the loss of the agricultural crops and the associated scarcity of food, as well as due to the destruction of the majority of the traditional residences, roads and embankments.

Partner in charge

World Meteorological Organisation (WMO) – Coastal Inundation Forecasting Demonstration Project, Consorzio Futuro in Ricerca

Members of the project’s end-users and stakeholders board

Bangladesh Water Development Board

Photo Gallery

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 Sandwip 1

Fig.1: Damaged home and the affected home owner, after the occurrence of an extreme event in Sandwip Island.

Sandwip 2

Fig.2: Damaged home and the affected home owner, after the occurrence of an extreme event in Sandwip Island.

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