Harun, IFCDR for his help in preparing some of the figures presented in this thesis. This study aimed to evaluate the environmental impact of the coastal embankment against flooding in Chittagong City. (3) the estimate of the height required to protect the area from flooding; and (4) assessing the environmental consequences of the embankment.
Evaluation of the effectiveness of the dam against wave flooding was done by estimating different types of damage faced by the dam during monsoon and cyclonic wave propagation. Although all age and professional groups responded positively to the environmental performance of the dam, it appeared that it did not show proper effectiveness against wave flooding during cyclone. Classification of respondents based on profession and age groups Answers from the local population about the project objectives.
Public opinion on the impact of embankment on irrigation water Public opinion on the impact of the embankment on fishery resources Survey results of the effect of project on communication. Public opinion on the impact of the project on employment opportunities and land value evaluation of the project as made by different occupations and age groups.
LIST OF PLATES
General
One of the main purposes of EIA is to give decision makers an explanation of the consequences of proposed courses of action before a decision is made. This type of checklist is useful for comparative evaluations of alternatives, and thus forms the basis for choosing the preferred alternative. Interaction matrices, as mentioned by Canter (1983), were one of the earliest types of methods used.
Summaries of the number of rows and columns designated as interaction provide insight into impact assessment and interpretation. The Environmental Evaluation Systems (EES) are used to evaluate the expected future conditions of the environmental quality, both 'with' and 'without the project. To determine value functions for an environmental parameter, Dee et al (I972) proposed a general approach as follows: . I) Gather information about the relationship between the parameter and the quality of the environment.
Divide the environmental quality scale into equal intervals, ranging between 0 and 1 (or 0 and 10), and determine the correct value of the parameter for each interval. The AEAM technique makes it possible to assess development projects in the light of the reality of such changes.
LITERATURE REVIEW
Beel Dakatia is one of the polders under the 'CEP' in the coastal area where the environmental degradation due to the project is beyond estimates and imagination. The main objective of this study is to assess the potential environmental impacts of the project. The main features of the hydrometeorological study and the delimitation of risk areas are shown below.
The study presents a detailed procedure for establishing the ground level of shelters in areas prone to growth. The IEB (1991) study is based on extensive field visits to the 1991 cyclone damage experienced in the coastal areas of Bangladesh. This chapter deals with storm surge analysis for overpass height prediction aiming at overpass flood risk assessment and embankment height calculation for overpass protection in the study area.
Increased wave height in northern Bangladesh as a result of the northerly convergent nature of the Bay of Bengal. Due to the flat slope in Chittagong, the height of the overpass and the length of the intrusion, in the study area, are always greater than any other part of the coastal area.
But the limitation of this model is that it does not account for the variation of surge along the coastline, but predicts a unique overtopping height for the entire coastal area. They tried to take into account the main factors affecting the amplification of the surge height and developed a nomograph (Fig.4.2). The fitted parabola was used to estimate the rise height from the pressure drop with an interval of 10 mb to 66 mb.
For the same cyclone intensity, the peak height varies significantly along the coast of Bangladesh, which is not taken into account in this model. To find the peak height for a pressure drop greater than 66 mb the following regression equation was applied; The equation is therefore applicable for estimating the peak height due to a pressure drop up to 66 mb.
Reid (1956) developed a model, shown below, for estimating the peak height when a hurricane moves perpendicular to the seacoast, assuming a triangular wind stress distribution and a linearly varying continental shelf bottom. Methods proposed by Reid (1956) and Bretschneider (1966) are capable of generating representative peak heights for linearly varying continental shelf bottom topography. The model takes into account the variation in peak height along the coast based on the length of the continental shelf.
The total displacement of the water surface rather than the peak height during a cyclone is interesting from a planning perspective. Maximum water displacement occurs when the wave height during spring tide is in the same phase as the tidal height. Eqno4.12 can be used to predict the maximum wave height at a specific location in the coastal area.
Thus, the predicted wave heights in Table 4.7 are average wave heights for a certain region. As a general rule, the wind wave height in shallow coastal waves can be assumed to be 1/2 to 3/4 of the wave height (Jelenianski, 1991). The MCSP (1992) study suggested that the height of local wind-induced waves would be one quarter of the wave height but not less than 1 m.
CD Tidal cree
Land Elevation
Acacia Catechu), rain tree (Samanea Saman), date palm (Phoenix dactylifera) and grow very well on both slopes of the dam. This is the phenomenon by which most parts of the embankment were damaged during the cyclone of 1991. Concrete blocks are used to protect seaward slopes of the embankment in the study area.
Since the rampart is built with local materials, it is not unlikely that these materials were used in the core of the rampart. The main reasons for the dam failure in the study area are thus the low height, poor construction materials and lack of compaction during construction of the dam. Part of the embankment was seen in good condition, although it was affected by surge during the 1991 cyclone (Plate 7.4).
Fish migrate to the floodplain and spawn during flooding, which is interrupted by the embankment. The country's largest Export Processing Zone, CEPZ was established in the project area behind the embankment. As can be seen from table 7.9, most of the respondents in the questionnaire think that the embankment can be used as a means of communication in the future.
The survey showed that the majority of respondents believe that the embankment has a positive impact on public health. This is because the construction of the embankment has provided many benefits. Fish Farming +3 L Fisheries are cultivated in closed ponds/lakes in the project area after the construction of the dike, as the intrusion of tidal salt water is closed by the dike.
The main focus of the study was to conduct an environmental assessment of the embankment in Chittagong. The environmental impacts of the embankment were addressed through extensive field investigations and questionnaire survey among 300 residents in the project area near the embankment. All age and professional groups responded positively to the impact of the embankment on the environment.
However, a negative response was received regarding the effectiveness of the embankment against natural floods during cyclones. The environmental impacts of the levee project were assessed through extensive field research and a survey.
REERENCES
APPENDIX-B
What are the goals of the project. i) Protection of agricultural land against saltwater flooding. ii) Protection of the area from cyclonic storm surge flooding. iii) Flood control, drainage and irrigation. If saltwater flooding could not be protected, what are the reasons. i) The embankment is partially built. ii) The required height was not provided. iii) The embankment was washed away by cyclonic storm surges. Did you feel safe from cyclonic storm surge due to the presence of the embankment.
What are your suggestions for cyclonic storm surge protection. ii) Increasing the height of the embankment. iii) Maintenance of the embankment must be done properly. iv) Broken parts must be reconstructed. What are pros and cons in communication as a result of the project. i) Boat communication is disrupted:. ii) Boat communication has stopped due to unavailability of water in the rivers/canals within the project area after the construction of the embankment. iii) Construction of new roads within the area as a result of flood protection. iv). What is the state of surface water availability to the shore. ii) Surface water is available. iii) Irrigation with surface water is possible due to timely supply of surface water. iv) Irrigation with surface water is impossible due to scarcity of surface water.
What water management techniques should be used for irrigation. i) Sufficient water must be supplied to the canals of the project area. ii) Number of low lift pumps (LLP) should be increased. iii). Channels should be constructed at the field stage. v) Water shall be distributed as per the decision of the committee constituted for irrigation planning. If there is congestion of drainage, what are the reasons. i) Insufficient number of drainage channels. ii) Water could not be drained out during high tide. iii) Construct more drainage channels.
If not suitable, what are the reasons. i) High salinity (ii) Other (iii) Don't know. a). What is the effect of embankment on canals/rivers. i) Rivers and canals in the project area were not silted (ii) Rivers and canals in the project area were silted jiii) Out of concept. What is the effect of the embalant on the salinity of the surface water. i) Salinity of surface water increases (ii) Salinity of surface water decreases (iii) Salinity of surface water remains unchanged.
What is the effect of embanlanent on the fertility of agricultural land. i) Fertility of agricultural land increases (ii) Fertility of agricultural land decreases (iii) Fertility of agricultural land remains unchanged (iv) Out of concept.
