Environmental Management Framework (emf) coastal embankment improvement project phase-i project (ceip-i) April 29, 2013 Dhaka Bangladesh Water Development Board Ministry of Water Resources Government of the People’s Republic of Bangladesh

4.2Physical Settings of the Coastal Regions

4.2.1Climate

61. 
    The climate of Bangladesh is dominated by sub-tropical monsoons characterized by wide seasonal variations in rainfall, moderately warm temperatures, and excessive humidity. Whole Bangladesh is divided into seven climatic zone, of which the coastal areas comprises three climatic zone – (A) South-eastern zone, (F) South-western zone and (G) South Central zone (Figure. 4.2). There are four prominent seasons in a year namely pre-monsoon (March-May), monsoon (June-September), post-monsoon (October-November), and winter (December-February).
    

61. 
    Temperature: In the coast zone of Bangladesh, maximum and minimum temperatures ranges from 30⁰C to 36⁰C and 11-23⁰C respectively (WARPO, 2006). Temperatures are higher in April and May while January is the coldest month of the year.
    

61. 
    Rainfall: In the coastal region of Bangladesh , annual rainfall increases from a little over 1,700 mm in the west to over 3,200 mm at Cox’s Bazar in the east. Heavy rainfall is most frequent along the east coast from Feni to Cox’s Bazar. Apart from the connectivity instability of the southwest air mass, the sea breeze reinforces the orographic lifting caused by the north south oriented hills of the Chittagong and Chittagong Hill districts. The foothills receive most of the downpours.
    

61. 
    Evaporation and Humidity: In the coastal zone low values of humidity are found during January- April and peak values during June-October. Evaporation exceeds rainfall only in the months of December and January. In all other months evaporation exceeds rainfall. Higher excess occur in the period May - October, and the lowest in February - April and in November.
    

61. 
    Wind: In the coastal zone wind blows mainly from two directions: NE and SE. The NE winds blow mainly in the winter season and the SE winds during summer. The maximum average wind speed is 80 km/ hr (50m/hr) ¹⁰.
    

4.2.2Land Use

61. 
    The coastal area of Bangladesh covers different types of land uses ranging from agriculture/fallow lands (63%), settlements (19%), water bodies/ rivers to forest (Figure. 4.3). The GTPW and CCP zones are mostly covered by mangroves and other forests. World’s largest mangrove forest – the Sundarbans is located in the southern part of GTPW zone, which is both locally and globally very important for its biodiversity and ecosystem services. The central zones – GTPE and MDP are covered by char lands, rivers and agriculture/ fallow lands.
    

61. 
    Inside the coastal polders, major land uses are agriculture/ fallow lands, settlements, road and river channels. About 64% and 30% of the total area of 139 polders is being used as agriculture/ fallow lands and settlements respectively. Shrimp firms and salt farms are included in the agriculture/ fallow land use pattern in this estimate. The shrimp farms are mostly located in brackish water areas throughout coastal zone, whereas salt farms are mainly located in the CCP zone.
    

4.3State of the Environment

4.3.1Water Resources

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    Coastal areas are endowed with both fresh and brackish water resources. The fresh waters are available in upstream part of rivers, ponds, wetlands and groundwater. Brackish waters are mainly in the estuarine part of the rivers and tidal cannels/ creeks. Major rivers flowing though the coastal area are Gorai – Madhumati -Baleswar river and Rupsha - Pussur river in the GTPW zone; Buriswar river in GTPE zone; Meghna river in MDP zone; and Karnafuli river and Feni river in CPP zone. Recent records of some water level stations in major rivers of coastal zone show that water level did not vary much over the past decade (Fig. 4.3). There is no available information on water discharge of the rivers in the coastal area.
    

Water level in Rupsa-Pasur river in GTPW zone	(b)Water level Barisal-Buriswar in river in GTPE zone
(c)Water level in Lower Meghna river in MDP zone	(d)Water level in Karnafuli river in CCP zone

61. 
    There are many beels, baors and ponds in the coastal area which are used as freshwater sources for people, fisheries and wildlife. Most of the beels and baors are located in the GTPW and GTPE zone. In addition, shallow groundwater aquifer provides almost 80% of drinking water supply to the coastal communities. Moreover, rainwater is being used in some areas through different rainwater harvesting technologies.
    

61. 
    During the monsoon, there is abundant fresh water, whereas during the winter, water scarcity becomes prominent. Due to reduced flows in the rivers in winter, both surface water and groundwater systems suffer from saline water intrusion, making the resource unsuitable for agricultural, domestic and industrial purposes. Furthermore, arsenic contamination in groundwater is becoming a severe threat to public health. Therefore, drinking water supply and irrigation for agriculture are important issues that need much attention of the concerned government authorities.
    

4.3.2Morphological condition

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    The coastal zone of Bangladesh comprises ‘Ganges Tidal Plain’ that lies in the west of the Meghna estuary (bounded by the Tetulia River) and ‘Chittagong Coastal Plain’ that lies in the south and east of the Meghna estuary.
    

61. 
    The Ganges Tidal Plain (West) is dominated by the Sundarbans forest, which covers the first 60 to 80 km inland from the coastline. Being a mature delta formation, the area has long drainage lines of low gradient. The rivers are sinuous and flow generally south through the plain. In recent decades and particularly since construction of the Farakka Barrage, there is little or no fresh water input from the parent river (the Ganges) during the dry season. Tidal flows extend far inland. Many polders have been constructed, some of them 150 km from the coast. Due to the movement of the tidal wave from west to east along the coast, there is a net flow in the same direction in interconnecting tidal channels between the main river channels. Tidal river channels have tended to silt up and reduce their capacity in response to the reduced tidal prism caused by empoldering land areas. As a result, maximum water levels and inland tidal range are higher than before, such as at Khulna.
    

61. 
    The Baleswar River forms the boundary between the west and east parts of the Ganges Tidal plain. The eastern part of the plain is characterized by a younger stage of estuary development; the land is intersected by a number of rivers drawing water from the Meghna, or from the Ganges via the Gorai or from Padma via the Arial Khan. There is no substantial forest area, and polders extend about 60 km inland from the coastline. The rivers are generally more active morphologically than in the western part of the plain. Wind waves erode the bank line at water level over the tidal range and currents cause erosion and steepening of the bank under water at the outside of bends, leading to shear failure. This results in migration of the rivers and erosion of polder embankments.
    

61. 
    The Chittagong Coastal Plain is a narrow strip of land along the eastern side of the Bay of Bengal with relatively short drainage lines between the hills to the east and the coastline. The rivers are steep and flashy. The flood flows are sediment laden and with the reduction in slope from the hills to the coastal plain, the river channels tend to become severely meandering. There are examples of recent meander cut-off in the Bharuakhali and Baghkhali rivers. In case of the Karnaphuli River, extensive river bank revetment and training works have been installed for the port which has prevented further morphological activity in the lower reaches. River flows are regulated by Kaptai Dam except at times of extreme floods.
    

4.3.3Sedimentation and Accretion

61. 
    Land erosion and accretion are common natural phenomena in the coastal zone. Major stable accretions were found in the coastal belt of Patuakhali and southern part of Bhola district. The past rate of net accretion in this region was 12 sq. km per year. Erosion at the rate of 3 sq. km and accretion at the rate of 15 sq. km took place in the last 20 years. Islands in this region may grow by silting up of small channels. The past trend of erosion and accretion may continue to follow for the next 25 years¹¹.
    

61. 
    Both erosion and accretion in the Meghna estuary region (i.e. northern part of Bhola district, Lakshmipur, Noakhali and Feni coastal belt, Hatiya arid Sandwip area) were found to be prominent. The past rates of erosion and accretion per year were detected as 20 sq. km and 28 sq. km respectively. So, net accretion rate was 8 sq. km per year. This past trend of erosion and accretion may continue in the future but the net accretion may be less. Major threat of erosion in the next 25 years may be in the region of northern part of Bhola, Lakshmipur coastline, north and northeastern parts of Hatiya, north and western parts of Swandip. Slow accretion may take place in the southern part of Hatiya and Noakhali mainland. Erosion and accretion in the Feni coastal belt is expected to be insignificant.
    

61. 
    Erosion and accretion in the regions of Harinbhanga River to Rabnabad channel and Feni River to Shahapari Island may be insignificant in the next 25 years. Small patches of erosions and accretions may take place here and there.
    

4.3.4River functionalities and estuary processes

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    Dynamic river and estuary processes are, of course, mostly to be seen in the Meghna Deltaic Plain (MDP), rather than in the other three areas. The Brahmaputra and Ganges rivers, via the Jamuna and Padma rivers, bring roughly two billion tons of sediment per year into the system, of which some 70% is fine material, very fine sand and silt. In comparison to this, the sediment from the Meghna River’s own catchment is negligible¹² (CERP-II, 2000). Most of the sediment is initially carried through the estuary and deposited in the Bay of Bengal. The shifting and sorting of the sediments is done by coastal and marine processes, like tides, waves and surges, as well as by fluvial ones.
    

61. 
    Near the head of the Meghna estuary, around Chandpur and upstream, the dominant processes are fluvial, resulting in braiding and the migration of the thalweg (deepest or main channel). Further downstream, tidal and salinity effects begin to have an influence also, but as far south as Ramgati the migration of the thalweg is the most important process. Dramatic thalweg migration in the much smaller estuary of the Feni River is also eroding a polder embankment. When a thalweg approaches a river bank it tends to erode the bank mainly below water level, so that an embankment built close to the bank will be undermined or outflanked by removal of soil below the level of its toe.
    

61. 
    In the seaward parts of the estuary, tidal processes tend to dominate over fluvial ones. In many parts the tidal flow is bi-directional, but the ebb and flood velocities are unequal (tidal asymmetry, leading to ‘tidal pumping’ of sediment). In other places, notably north and west of Swandip Island, ebb and flood currents follow different routes (mutually evasive currents). In both cases tidal action moves sediment, often towards inland direction. Under some circumstances sediment can be trapped.
    

4.3.5Air water and noise quality

61. 
    Air quality: Air pollution is not much significant concern in the coastal area of Bangladesh. Major emissions are coming from road and river transports and industries (e.g. cement factories, petroleum industries, power plants). Ambient air quality (mainly three parameters - SPM, SOx, NOx) was tested in eight locations in the entire coastal area (4 urban and 4 rural) (Table 5.1). It is observed that the present air quality parameters are within standard limits in most areas, except high SPM in Khulna city, Chittagong, Cox'sbazar and Noakhali town mainly due to high traffic loads.
    

61. 
    Surface water and groundwater Quality: Domestic sewerage, industrial wastewater, oil spill from water transports are the major source of water pollution in the coastal area. Surface water quality of some major rivers and ponds were tested in coastal region (Table 4.3), which showed that most of the water quality parameters were within standard limit. pH and electrical conductivity (EC) values indicates that both river and pond water were saline. Also high concentration of coliform was found in pond waters. In addition, groundwater quality was tested through collecting tube-well water samples from eight different locations in coastal areas (Table 4.4). It was observed that most of the water quality parameters are within threshold limit with exceptions in few locations (e.g. high Chloride in Khulna city, high iron content in Noakhali town and high concentration of Arsenic in Noakhali area) (Table 4.4). In general, higher Chloride content, i.e. salinity was found in all tube-well.
    

61. 
    Noise quality: Noise quality was tested for day and night in eight locations (both urban and rural) of 6 coastal districts (Table 4.5). Noise quality was found above standard level both in day and night time in some urban and rural areas.
    

4.3.6Soil and Agriculture

61. 
    The coastal area of Bangladesh is included mainly under Agro-ecological region 13: Ganges Tidal Floodplain, 18: Young
    

61. 
    Meghna Estuarine Floodplain and 23: Chittagong Coastal Plain. It represents part of extensive area of tidal floodplain land with smooth relief crossed by innumerable tidal rivers and creeks. River banks generally stand higher above the adjoining basins. The area is mainly shallowly flooded at high tide, either throughout the year or only in the monsoon, except in the extensive areas where tidal flooding is prevented by embankment. Within embankments, there is seasonal flooding with accumulated rain water.
    

61. 
    In the coastal area, several soil types occur, varying in texture from sandy loams to heavy cracking clays. Most of the soils of the coastal area are saline and non-calcareous, except for some soils of the Old Ganges and Meghna floodplain areas. Most of the soils of the coastal zone are moderately to strongly alkaline.
    
62. 
    The coastal region covers about 3.6 million acres of Net Cultivated Area (NCA) with average cropping intensity of 175%, where mostly local and hybrid rice crops are grown¹⁴. The 139 polders cover a gross area of about 1.12 million ha, of which about 64% are available for crop cultivation. Agriculture practices in the coastal zone are mainly rain-fed cropping and irrigated cropping system (Figure 4. 5).
    

61. 
    On highlands under rain-fed condition, the major cropping sequences are local/HYV broadcast Aus followed by local/HYV transplanted Aman, and local broadcast Aus followed by a wide range of Rabi crops depending on the residual soil moisture.
    

61. 
    A wide variety of Kharif vegetables are also grown in place of Aus in areas having suitable soil characteristics and serviced by highways and arterial roads. Locally, jute is the main cash crop, replacing broadcast Aus in the cropping pattern. Kharif vegetables are also grown replacing broadcast Aus or jute. Occasionally, a short duration Rabi crop (wheat/vegetables/pulses) is cultivated between the main cropping sequences as a third crop, primarily depending on residual soil moisture in the early Rabi season.
    

61. 
    On medium highland, intermittently flooded up to 90 cm, local / HYV broadcast Aus is followed by local / HYV transplanted Aman as the major cropping sequence. Rabi crops like wheat, pulses, oilseeds, vegetables, spices and minor cereals are also cultivated either as a third crop or as a second crop after transplanted Aman.
    

61. 
    On medium lowland early broadcast Aus or late transplanted Aman is grown to avoid damage from flooding, which starts in June and peaks in mid-August. Jute, followed by wheat or potato, is also grown on this land type.
    

61. 
    On the edge of basins, broadcast Aus is grown followed occasionally by pulses, mainly Khesari (Lathyrus), a low value legume, with mustard as Rabi crop. Minor lowland, is transplanted with HYV Boro crop, if not sown with broadcast Aman in late February/March as a single crop. In the double cropped areas, Rabi crops e.g. wheat, potato and some vegetables are grown following broadcast Aman or Aus. Because of vulnerability to flood damage, no other Kharif crops are grown.
    

61. 
    Irrigation water for crop production in the dry season is very scarce except a small area managed under irrigation schemes. About 13% of the net sown area (or 7.80% of the total cropped area) is irrigated by a mixture of mechanical (STW and LLP) and indigenous (HTW, Don, Swing Basket, etc) irrigation means. Deep tube-wells are almost absent. Irrigation by STW is generally concentrated in the F₁ area because of the need to site the equipment on higher ground to avoid submergence by flood. STW and LLP are used to irrigate high, medium high and medium lowlands. The indigenous methods are normally practiced to irrigate crops situated near the source of surface water. HYV Boro is the major recipient of irrigation and is normally preceded by rain-fed transplanted Aman. HYV potatoes, wheat and a portion of the Rabi vegetable areas are also irrigated. Supplementary irrigation for wetland crops is practiced and transplanted Aus receive sometimes one or two irrigation during the land preparation stage. In years with insufficient rainfall, transplanted Aman is given supplementary irrigation particularly during the flowering stage in October.
    

61. 
    Agricultural practices are based on soil and land type, availability of irrigation, demand of crop products, etc. The existing cropping pattern is predominantly rice based. Rice covers a major portion of the total cropped area (approximately 75%). The remaining area includes other crops in both Kharif and Rabi seasons. Rabi crops are wheat, winter vegetables, bean, cowpea, pulses, oilseeds, potato, sweet potato, chili, cowpea, millet, water melon, ground nut, etc.
    

61. 
    Overall, the following are the important issues in ‘agriculture’ sector related to CEIP :
    

• 
  Soil salinity is the most dominant limiting factor for agriculture practices in the region, especially during the dry season.
  
• 
  Scarcity of quality irrigation water during dry season limits cultivation of boro rice and rabi (winter) crops, and aus cultivation during kharif-1 (March-July) season.
  
• 
  Variability of rainfall, uncertain dates of onset and recession of seasonal floods and risk of drought restrict cultivation of aus and aman rice.
  
• 
  Perennial water-logging due to inadequate drainage and faulty operation of sluice gate facilities restricts potential land use within the polder areas.
  
• 
  Difficult communication and remote marketing facilities also retard agricultural development of the region.
  

4.3.7Fisheries

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    The coastal fishery mainly consists of two types of fishery, such as capture and culture fishery in the fresh to brackish water environment. Capture fisheries are categorized into three different fish habitats namely Rivers and canals fishery, Marine Artisanal fishery and Post Larvae (PL) fishery. Similarly Pond/ditches and Shrimp Ghers are the habitat category of culture fishery. The fish habitat are presented in Figure 4.6
    

River/ canals	Ponds/Ditches	Gher

61. 
    The major species of capture (both brackish and fresh) fishery include Hilsha (Tenualosa ilisha), Bhetki (Lates calcarifer),Poa (Pama pama),Parsia (Liza parsia),Tapasi (Polynemous paradesious), Tulardanti (Sillago domina), Phasa (Setipinna phasa), Bagda (Penaeus monodon) etc. The composition of coastal capture fisheries are presented in Appendix - 2. In 2008-2009, the coastal zones capture fisheries production of rivers, beels, Baors, floodplains and Sundarbans is about 340,128 metric ton.
    

61. 
    Two forms of aquaculture are practicing in the coastal zone such as fish culture (mainly fresh water species) and shrimp. The pond fish culture is found more in the polders of Ganges Tidal Plain West and East, Meghna Deltaic Plain (MDP). The pond/ditches are mainly cultured with white fish and the Ghers are cultured with shrimp as mono culture and shrimp along with white fish/prawn as mixed culture. Most of the ponds having the average size of 2000 sq. ft. are polyculture ponds. The three most commonly used fish species in pond aquaculture are major carps Rui (labeo-rohita), Catla (Catla catla) and Kalibaus (Labeo calbusa). Other culture species include common carp (Cyprinus carpio), Grass carp (Ctenopharyngodon idellus), Silver carp (Hypophthalmichthys molitrix) and two Tilapia species (Oreocromis mossambicus and Oreocromis niloticus), Pangas (Pangasius sutchi) etc. In 2008-09, average yields from different ponds was 2853 kg/ha in the coastal zone while country average is 3141 kg/ha. However, average yields were 3102 kg/ha for the culture ponds, 1584 kg/ha for the culturable ones and only 910 kg/ha for the derelict ponds.¹⁵
    

61. 
    In the CEIP area, the total cultivable land area is about 931,300 ha of which shrimp farm covers 89,200 ha. Most of the shrimp farms are found in the polder area of Khulna, Bagerhat, Satkhira, and Cox’s Bazar districts. The Gher culture fishery includes Bagda (Penaeus monodon, P. indicus), Golda (Macrobrachium rosenbergii),Baila (Glossogobius giuris),Golshatengra (Mystus sp) etc. In 2008-2009, the fisheries production of Gher (Shrimp/Prawn, fish) in the coastal area was about 668 kg/ha. Over the last 30 years the significance of the shrimp has grown rapidly in the coastal zone. The shrimp farms play a major role in employment, and foreign exchange earning in Bangladesh. According to DoF statistics, the shrimp production in the coastal zone amounted to 99.89% of the country’s total in 2008-2009. It is the second biggest foreign exchange earner for the country.
    

Hilsha (Tenualosa ilisha)	Bagda shrimp (Penaeus sp)	Baila(Glossogobius giuris)

61. 
    Although the coastal area is rich in capture fisheries especially brackish water fisheries, presently the culture fisheries like shrimp culture practices is increasing extensively in southwestern and south eastern zone. Therefore, the mono fish culture will be increased which will influence the increasing of specific fish species. On the other hand, salinity intrusion due to sea level rise could reduce habitat for fresh water fish in the coastal area. Consequently, production of freshwater fisheries may be hampered as the species of fresh water carp, catfish, perch etc. are highly susceptible to moderate level of salinity.
    

61. 
    The major problems and issues of fisheries sector in the coastal area are as follows:
    

• 
  Morphological changes in rivers, poor fisheries management and changes of aquatic ecological conditions;
  
• 
  Decreasing of fish habitat and depth due to siltation;
  
• 
  Increasing salinity in surface water;
  
• 
  Losing floodplain fisheries due to extensive shrimp culture practices;
  
• 
  Obstruction of feeding and spawning migration due to inadequate migratory routes between rivers and different internal water bodies;
  
• 
  Poor fish marketing system and post harvest facilities due to poor communication and infrastructure.
  

4.3.8Ecosystems and Biodiversity

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    Bio-ecological zone: The coastal zone of Bangladesh falls in ten different bio-ecological zones namely the Ganges floodplain and Major rivers, Coastal marine water, Meghna floodplain, Sundarbans, Chakaria Sundarban, Coastal plains, Offshore islands, Meghna estuarine floodplain.
    

61. 
    Ecosystems: The coastal area is enriched by different type of fresh to brackish water ecosystems due to its ecological and physical settings. The ecosystems of the region can also be classified as per habitat type, i.e. marine, brackish water, freshwater, mangrove, Sundarbans, floodplain, island, peninsula, and terrestrial ecosystem (roadside and homestead). Moreover, shrimp farming pond (Gher) ecosystem are found in this area.
    

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    Protected Areas: There are different types of ecosystem management approach applied to protect vulnerable ecosystems in the coastal region of Bangladesh, such as declaring Ecologically Critical Area (ECA), Ramsar site, National Park, Wildlife Sanctuaries, Eco-park, Game Reserve, World Heritage Site, Marine Reserve and Fish Sanctuaries. The protected areas in the coastal zone are presented in Appendix 3. Some of the coastal polders fall within these protected areas, mainly within the 10 km peripheral area of the Sundarbans Reserve Forest which is declared as ECA (in Satkhira, Khulna and Bagerhat district). Relevant rules and regulations need to be followed while undertaking any development activities in these protected areas.
    

61. 
    Common flora and fauna: The coastal zone has a good terrestrial and aquatic environment that provides habitat for a large number of flora and fauna.Hargoza (Acanthus illicifolius), Narikel (Cocos nucifera), Khejur (Phoenix sylvestris), and Bhadi (Lennea coromandelica) are the native dominant flora. Jackal (Canis aureus), Grey mask shrew (Suncus murinus) and small Indian civet (Viverricula indica) are the dominant native mammals and randomly found in the area where shrimp farming is limited. Saurs crane (Grus antigone), Black-winged stilt (Himantopus himantopus), Little grebe (Tachybaptus ruficollis), Red-wattled lapwing (Vanellus indicus) were once commonly seen in this region but rarely found at today. Ring lizard (Varanus salva), Banded sea snake (Hydrophic fasciatus), Estuarine sea snake (Hydrophic obscura), etc are the common reptile in this region but rarely found in the area of intensive shrimp farming practices. The common flora and fauna habituating in this region are listed in Appendix 4.
    

4.3.9Mangrove forest

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    The southwestern part of coastal region houses world’s largest mangrove forest- the Sundarbans. The mangroves forests are transitional zones between fresh and marine waters, and are rich in marine and terrestrial flora and fauna. Also, the mangrove forests serve as a natural fence against cyclonic storms and tidal surges, stabilize coastlines, enhance land accretion, and enrich soil near the aquatic environment. The Sundarbans Reserve Forest occupies an area of 601,700 hectares of which 406,900 ha forests, 187,400 ha water (rivers, rivulets, ponds, and canals), and 30,100 ha form wildlife sanctuaries, and 4200 hectares are sand bars.
    
62. 
    The mangrove forest is very rich in biodiversity and supports 334 species of plants, as many as 77 insects of different orders, 7 crabs, 1 lobster, 23 shrimp/prawns, 400 fish, 8 amphibians, 35 reptiles, 270 birds, and 42 species of mammals. There are about 13 and 23 species of orchids and medicinal plants respectively found in the Sundarbans.
    

61. 
    The Sundarbans was declared a World Heritage Site in 1997 by UNESCO. It is known as the single largest stretch of productive mangrove forest in the world, and is inhabited by one of the most elegant creatures of nature, the Royal Bengal Tiger (Panthera tigris), and estuarine crocodiles (Crocodylus porosus) occur extensively in the rivers. The Sundarbans is also home to thousands of spotted deer (Axis axis). There are large numbers of threatened wildlife species including Python, King Cobra, Clawless Otter, etc.
    

61. 
    Among the commercially important plant species in Sundarbans, the two dominant ones are the Sundari (Heritiera fomes) and Gewa (Excoecariaag allocha). Among the trees, Gewa and Goran (Ceriops roxburghiana) are being used in newsprint mills for paper production, as well as for fuel-wood. Sundari and Keora (Sonneratia apetala) are used as timber woods. The most important non-wood forest product is Golpata (Nypa fruiticans). Leaves from this plant are widely used for thatching of roofs of houses and boat and also for fencing the houses of millions of families around the coastal districts. According to Forest Department, 2010, the production rate of timber, fuel wood and thatching materials (Golpata) was about 3567 m³, 120 tonnes, 26653 tonnes per year respectively during 2001-02 to 2009-10 .
    

61. 
    The forest resources and biodiversity of Sundarban are vulnerable to natural hazards like cyclone and storm surges as well as the threat of over exploitation. The cyclone Sidr (in 2007) caused immense loss of biodiversity of Sundarban and its adjacent areas. Sea level rise due to climate change is another threat to biodiversity of Sundarban. It is predicted that the Sundari in the mangrove forests are threatened due to increased salinity. Moreover, municipal wastewaters, industrial pollution, oil pollution, ship breaking etc. are harmful to coastal and marine biodiversity especially in Chittagong and Khulna region.
    

61. 
    Sundarbans the largest Mangrove forest of South Asia is in close proximity of the 6 districts of 17 polders. Bagerhat, Sathkhira and Khulna are within the impact zone of Sundarbans (10 km buffer area outside the Sundarbans). Rehabilitation and reconstruction of polders may have indirect impact on the water flow quantity and pattern within the channels of Sundarbans.
    

4.3.10Natural Hazards and Disasters

61. 
    Cyclonic storms are an important feature of the Bangladesh climate and have been inflicting suffering to people and enormous damage to structures. During the last 125 year, cyclones hit the coastal belt: 14 occurred during the last 25 years. Two different types of cyclones form in the bay – (i) tropical cyclone, which forms during the pre- and post-monsoon seasons, and (ii) monsoonal depression, which develops during the monsoon season.
    

61. 
    Cyclones generally cause damage in three different ways: (a) storm surges (b) flooding due to excessive rainfall and (c) wind blowing away houses and ships. About 90 per cent of cyclone casualties are caused by storm surges generated by cyclones. Also, there is a fourth way that can cause damage, i.e. extreme winds can create wind waves which are superimposed on the surge. These waves damage the embankments and run up the embankment slope. If the volume of wave overtopping is excessive, the water is carried over and erodes the country side slope of the embankment. This is very important in embankments that face the sea or wide estuaries which allow the waves to build up strength because of the long “fetch”. For example, in Baleswar (polder 35/1, Figure 4.8), the slope was reduced to 1:5, slope roughness elements were added, but an additional 1.5 m still had to be added to the crest level to keep the wave overtopping volume within limits.
    

61. 
    Storm winds blow at speeds of up to 240 km per hour cause widespread damage. The high number of casualties is due to the fact that cyclones are always associated with storm surges. Storm surge height in excess of 9m is not uncommon in this region. According to WARPO 2005, the 1876 cyclone had a surge height of 13.6 m and in 1970 the height was 9.11 m. In fact, the 1970 Cyclone is the deadliest cyclone that had hit Bangladesh coastline. With a wind-speed of about 224 km per hour and associated storm surge of 6.1 to 9.11 meters, it was responsible for death of about 300,000 people. In 1991 cyclone (wind speed: 225 per hour , storm surge: 6.0-7.6 Meters), total casualty was 138,882.
    

61. 
    The cyclone Sidr-2007 (wind speed: 240 per hour , surge height: 4.5 - 6 Meters (15-20 feet)) affected 12 coastal districts -Barisal Patuakhali, Barguna, Pirojpur, Jhalokathi, Bhola, Bagerhat, Khulna, Satkhira, Shariatpur, Chittagong and Cox’s Bazar and their offshore islands and chars received the major destructions by the Sidr. Out of 12 severely affected districts, these Bagerhat, Barguna, Pirojpur and Patuakhali were the worst affected. It was observed that 3,363 people died and 55,282 were injured. Approximately 5,64,967 houses were totally destroyed and 9, 57,110 houses were partly damaged. It is also reported that 7,43,321 acres (300812 ha) of crop areas were fully and 17, 30,316 acres (700235 ha) area partly damaged by the Sidr’2007 .¹⁶
    

61. 
    The coastal area has faced another devastating cyclonic storm surges called ‘Aila’. Cyclone Aila hit 14 districts on the south-west coast of Bangladesh on 25th May 2009. About 2.3 million people were affected by Aila and many of them were stranded in flooded villages as they had no alternative to save themselves. The Cyclone Aila furiously hit the Satkhira and Khulna Districts of Bangladesh. The Aila caused massive damage to coastal polders and embankments and submerged to the villages. A study conducted by Unnayan Onneshan, in 2009 revealed that among the affected districts, Satkhira received the highest amount of impacts in its infrastructures. 734 educational institutions including the religious institutions, 329.25 km roads, 41 bridges or culverts, 292.42 km embankment and 26028 ha shrimp farm (gher) were fully or partially damaged. The study also revealed that 734 institutions were damaged fully or partially. The adverse impacts of Aila were observed in 7 upazilas and 48 unions of Satkhira District. However, Shyamnagar and Ashasuni are the most affected upazila as reported by the local source and available data. More than fifty thousand people were adversely affected by Aila flooding. On the other hand, total damaged cropland was about 1250 ha. Moreover, 59 people died and 1509 were injured during Aila.
    

61. 
    Parts of the coastal zone are occasionally subject to river floods which cause major hardship, loss and damage. In the coastal area, extreme floods occurred in 1974, 1980, 1984, 1987, 1988, 1998 and 2000. Near the Meghna estuary these are a natural consequence due to the presence of two very large incoming international rivers, the Brahmaputra and the Ganges, as well as local catchments. Elsewhere, especially in the CCP, they are generated by the prevalent high rainfalls, especially those associated with cyclones. In both cases the flooding is exacerbated by the generally low gradients of land and rivers in the plains. It is reported that extreme flood occurred in Satkhira in 2000. The duration of flooding water was three months. Flooding event caused immense damage to crops and shrimp gher of the Satkhira district. According local people, such type of flood did not occur in the last 60 years. The Kaligonj road was submerged up to 10 feet due to flooding. On the other hand, flood in 1988 and 1998 affected the roads, houses, market places, educational institutes, forest resources, fish pond and crops of different upazila of Cox’s Bazar extensively. Flooding water flow over the homestead, roads, and polders more than 5 feet and stayed for few months.
    

61. 
    Many parts of the coastal area of Bangladesh is facing water logging problem, especially in southwestern region (Khulna, Satkhira, Jessore districts) and Noakhali region (Figure. 4.9). Water logging is created due to natural process of sedimentation in the river and drainage channels as well as improper maintenance of regulators and drainage channels in the coastal polders. Sedimentation in the peripheral rivers and the subsequent loss of tidal range has made it impossible for some polders to be drained as was done previously though the drainage regulators. Also embankment of some polders was breached by the tidal surge during cyclone ‘Sidr’ and ‘Aila’ and low lying lands inside coastal polders are inundated. About 30% of all polders are now experiencing water logging in the coastal area. Recent remote sensing images show that water logging is occurring mainly in southwestern region (Bagerhat, Khulna and Satkhira) of coastal zone (Figure 4.10). Water logging in the coastal polders affected almost all livelihood activities (agriculture, fisheries), and road infrastructures.
    

61. 
    Soil salinity: Saline or salt affected soils are common in coastal area of Bangladesh. Soil Research Development Institute (SRDI) in 2010 states that out of about 1.69 million ha of coastal land about 1.06 ha are affected by soil salinity of various degrees. Most of the lands within the Khulna and Barisal division are affected by salinity. The critical salinity level for agriculture is 1 to 5 ppt, for Sundari growth it is in the range of 10 to 15 ppt. Optimum shrimp production is between 10 and 20 ppt. The soil salinity in the coastal area is shown in Figure 4.11. Figure shows the total coastal area affected by low, moderate and high salinity level. The soil of Satkhira, Khulna, Patuakhali (Char land), Bhola (southward) and Chittagong (Swandip) districts are severely affected with strong salinity. North part of Khulna, Bagerhat, Barguna, Pirojpur, Noakhali and Cox’s Bazar are affected by moderately to strong salinity.
    

61. 
    Surface Water Salinity: Saline water intrusion in coastal area is highly seasonal in Bangladesh. Salinity and its seasonal variation are dominant factor for coastal ecosystem, fisheries and agriculture. Therefore, any changes on present spatial and temporal variation of salinity would affect the biophysical system of coastal area. During dry season (December to March) deep landward intrusion occurs through various inlets in the western part of coastal zone and through Meghna Estuary. Except Tetulia, Meghna, Kakdon, Subidkhali, Lebukhali, Laukathi, Kukua, Gopaldi, Kajal, Tajumuddin canal under Noakhali, Bhola, Patuakhali, Barisal, Jhalokathi districts almost all the rivers remain highly saline in dry season¹⁷. Almost all the rivers of Jessore district remain saline. Maximum salinity variation in dry season is shown in Figure 4.12. In dry season, 5ppt isohaline intrude more than 90 km landward at the western part of the coastal area in the Sundarbans through Jamuna-Malancha-Raimangal river. Freshwater flow decreases in the Pasur-Sibsa river system during dry season, the saline front moves upward by 30-40 km. In the Baleswar-Bishkhali river systems, in the dry season 5ppt saline front moves landward by 20-25km from the coastline. In the middle part of coastal zone along the Meghna estuary, landward salinity intrusion is low because of huge freshwater flow coming through the Meghna river system.
    

Figure 4 12: Surface water salinity (dS/m, maximum in January 2010) distribution in coastal area

61. 
    It is an ongoing disaster and there is no specific indicator to measure the extent of damage. River erosion in Bangladesh is no less dangerous than other sudden and devastating calamities. Losses due to river erosion occur slowly and gradually. Though losses are slow and gradual, they are more destructive and far-reaching than other sudden and devastating calamities. The effects of river erosion are long term. The disastrous riverbank erosion events are mainly associated with the major river systems of the country and are seen along the banks of the Brahmaputra-Jamuna, the Ganges-Padma, the lower Meghna, and other rivers. River erosion in the coastal area is not prominent than other part of the country. The disastrous river bank erosion mainly occurred in the lower Meghna River. The victim districts are Chandpur, Shariatpur and Bhola. River erosion not only causes displacement of people in this area, it also leads to massive financial loss
    

61. 
    Arsenic contamination is considered to be a dangerous environmental threat and a serious health risk. It is identified as a public health emergency in Bangladesh. There is no specific treatment for chronic arsenicosis other than ceasing further intake of arsenic contaminated water and raising awareness of the population about the problem. The value (recommended limit) for arsenic in drinking water as per the guideline of the World Health Organization (WHO) is 0.01 mg/L while the national standard in Bangladesh, is 0.05 mg/L. With varying levels of contamination from region to region, groundwater in 61 out of the 64 districts in Bangladesh is contaminated with arsenic. According to a study conducted by the British Geological Survey and DPHE, about 57 million people in Bangladesh drink water that has an arsenic concentration greater than the WHO guideline value and up to 35 million people drink water that has concentrations in excess of the Bangladesh standard. Figure 4.13 shows that waters in the southwest and southeast parts of Bangladesh are highly contaminated with arsenic more than 0.05 mg/l, especially in Chandpur, Noakhali, Feni, Laxmipur, Khulna, Bagerhat and Satkhira districts.