ASSESSMENT OF THE POTENTIAL OF BIOENGINEERING INTERVENTION TO MOVE COASTAL CYCLONIC WIND AND STORM DEVELOPMENT. In addition, I am grateful to all the faculty members, students and staff of the Institute of Water and Flood Management for their help. Bangladesh is visited by tropical cyclones almost every year due to the geographical location of the country.
The western coastal zone of Bangladesh is protected by a buffer zone in the form of the Sundarbans mangrove forest. NDVI analysis of the coastal zone of Bangladesh between the 1990s and 2020s found that the central coastal zone traditionally lacks dense vegetation. However, an increase in the extent and density of vegetation has been observed through the data analysis indicating the positive impacts of the recent afforestation initiatives.
Semi-structured interviews had been conducted to extract primary data and the data has been analyzed to collect the perception of local people and interpret their attitudes towards an expansion of bioengineering measures. Through synthesis and interpretation of the data, it has been shown that there is widespread awareness among the local coastal residents of the beneficial effects of a forest buffer on the coast.
INTRODUCTION.................................................................................. 1-3
- Objectives
- Scope of the Study
- Limitations of the Study
- Organization of the Thesis
In this study, the question of the potential of bioengineering intervention to delay cyclonic storm surges and high wind speeds in coastal Bangladesh will be explored. This study will provide a unique perspective by bringing together technical and social aspects in the context of Bangladesh. This study captures a representative scenario of the total coastal area of Bangladesh rather than each coastal district, due to the resource constraints required to conduct a larger study.
Acquiring six separate satellite images of the Landsat satellites was necessary to cover the entire coastal zone of Bangladesh for the NDVI analysis in one year. The availability of six satellite images with minimal cloud cover from consistent months in a year was difficult in some of the years analyzed; but consistent periods have been maintained where possible. The limitations related to the satellite imagery (such as the Scan Line Corrector error in Landsat 7) apply to this study.
Some secondary data values (recorded wind speeds and water levels) were missing from the collected data, which may have been due to the malfunctioning of the survey meters or maintenance purposes – the use of such data was avoided where possible. Chapter One describes generalized concepts, background and current state of the problem with rationale and specific objectives of the study.
LITERATURE REVIEW...................................................................... 4-11
- Cyclones and Strom Surges
- Hard Engineering Options
- Soft Engineering Options
- Bioengineering
- Summary
The BMD data obtained classified the cyclones as indicated in the "Nature of the Phenomenon" column of the table. It can also be concluded with high confidence that the dominant cause of global average sea level rise since 1970 is anthropogenic forcing. Part of the appeal of hard technical options is the seemingly cheap and simple solution in the short term.
Another aspect of tough technical measures is that they can give a false sense of security. Tough technical measures can lead to an increase in commercial development right next to the hard protective structures. Particularly in the context of coastal zone management, there is a growing recognition of the benefits of soft protection and its adaptation strategies (Klein et al. in their study proposed nature-based adaptations and soft solutions that are complementary to hard solutions.
Bioengineering was abandoned in the mid-twentieth century, but has recently seen a resurgence. This underpins the need to assess the potential of bioengineering in the coastal region of Bangladesh.
STUDY AREA........................................................................................ 12-14
- Locaton and Geology
- Population and Demography
- Infrastructure and Industries
- Introduction
- Combining Qualitative and Quantitative Techniques
- Normalized Difference Vegetation Index
- Data Collection
- Primary Data Collection
- Secondary Data Collection
- Summary
The central coastal zone extends from the mouth of the Feni River to the eastern corner of the Sundarbans and covers the districts of Noakhali, Barisal, Bhola and Patuakhali. Soil characteristics in the western coastal zone are silty clay or alluvium and the soil formations are of recent origin (Islam, 2003). However, the population density in the inner coast is much higher than that in the outer coast, and according to Islam, the percentage of households in the coastal zone is absolutely poor.
A significant road network is present in most of the coastal area currently according to the LGED map of paved roads in the upazilla levels of Bangladesh (Figure 3.2). Almost all the small and big cities of the coastal area are connected to the capital Dhaka by waterways (Sarwar, 2005). The numerous tidal rivers in the coastal zone form an integral part of the general characteristics of the region.
Data analysis was performed to investigate any trend or other statistically significant features inherent in the datasets. The purpose of this analysis was to determine the extent and density of coastal vegetation in the coastal belt of Bangladesh and to observe changes in vegetation cover over the years.
DATA SYNTHESIS AND RESULTS................................................... 26-67
Secondary Data Analysis
- NDVI Analysis
- Wind Speed Data Analysis
- Water Level Data Analysis
- Secondary Data Synthesis
A plot of five-year average data of areas falling into different NDVI classes also seems to confirm this idea, showing a decrease in dense vegetation while showing an increase in the extent of less dense vegetation (Figure 5.10). From 2010 to 2014, there appeared to be a decrease in the area with denser vegetation (Figure 5.11), as well as some randomness in the short range of data. However, it appears to have improved slightly and there is a slight upward trend in this area with denser vegetation from 2015 to 2020 (Figure 5.12).
Primary Data Analysis
The stations of the western coastal zone are located behind the Sundarbani, which provides them with vegetative buffers that impede the cyclonic effects. Respondents in the southwest coastal area were from Satkhira and Khulna, two large districts of Bangladesh. Due to the disaster-prone nature of the region and memories of recent disasters, most people are acutely aware of vulnerabilities and threats.
They also appeared to be very aware of the protective nature of the Sundarbans and the important role it plays in mitigating cyclonic winds and storm surges. Respondents from this region universally recognized that the Sundarbans bore the brunt of the Sidr and protected countless lives and property. They also cited the cooperation of local people in helping the Sundarbans recover from the damage to their ecosystem incurred due to the Sidr.
Respondents showed gratitude and love for the mangrove and concern for the future of their protective barrier (Table 5.24). Respondents from the central coastal area of Bangladesh were also familiar with natural disasters such as cyclones. Most respondents from this area were in support of major engineering works such as sea walls and large stretches of high embankments.
They shared experiences of plantation on the sides of the river banks which reduced the erosion and helped to stabilize the river reach in some stretches, especially upstream of the interface of the lower Meghna and the Bay of Bengal. Most of the undergraduate and postgraduate level educated respondents from this region recommended an integrated green barrier system, which includes the structural measures and non-structural measures (Table 5.25). The opinions of the respondents were divided as some felt that the protective effects would not apply.
The respondents from the eastern coastal area were familiar with the uninterrupted continuous coastline of the region. The respondents of this region are familiar with frequent cyclones, and the urban development of this area is also mainly adjacent to the coastline. The respondents mentioned their recognition of the effectiveness of green barriers on the southern coast, but most of them were aware of the space requirements, and expressed their doubt that bioengineering is useful in this particular area.
Synthesis of Primary and Secondary Data
- Technical Aspect
- Social Aspect
- Environmental Aspect
- Economic Aspect
Respondents in the central and eastern coastal zones also seemed to be very aware of the effects of coastal buffers, but they generally tended to focus more on the structural measures. Respondents also highlighted the associated benefits of biotechnical interventions, such as prevention of soil erosion and mudslides in the hilly areas. Some of the respondents have suggested that a setback area could be designated in the future if such a policy is adopted.
From memory, the respondents recounted the rich biodiversity in the coastal areas, which are the main resources for the people living in this region. Respondents specifically highlighted the lack of monitoring of industrial waste discharges and the lack of proper solid waste management that plagues almost all major industrial districts (ie Khulna, Chattogram) in the coastal region of Bangladesh. The benefit of the coastal buffer zone in stabilizing the soil in the coastal area and preventing erosion-related disasters will also be very important in this area.
The heavy engineering measures commonly used in the coastal region usually involve heavy construction with concrete and steel structures. Therefore, the bioengineering strategy in combination with hard engineering measures is also economically very effective and has a high untapped potential in the case of Bangladesh. This thesis work aimed to investigate the potential of one of the soft engineering measures namely bioengineering in the form of green coastal buffers in the coastal zone of Bangladesh to mitigate the destructive effects of cyclones.
Primary and secondary data were collected using freely available satellite imagery, wind speed data, water level data and semi-structured interviews with respondents living in the coastal area of Bangladesh using a mixed research method. It was found that the western coastal area is largely protected by the Sundarbans, while the eastern coastal belt has mangrove belts in elongated forms. As found through the analysis of primary data, people in the coastal area are aware of the buffering effects of green coastal forest or mangrove cover from their previous experiences with cyclones and have a positive opinion of increasing forest cover to reduce storm surge and soil erosion.
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