Ainun Nishat

River salinity and climate change: evidence from coastal Bangladesh

In a changing climate, saltwater intrusion is expected to worsen in low-lying coastal areas around the world. Understanding the physical and economic effects of salinity ingress, and planning adaptation, are key to the long-term development of countries for which sea level rise has been identified as a major risk from climate change. This paper presents a study conducted in Bangladesh, which quantifies the prospective relationship between climate-induced changes in sea level, temperature, rainfall, and altered riverine flows from the Himalayas, and the spread and intensity of salinization on river water in the coastal zone for 2050. The research takes into account the projected land subsidence of the Ganges Delta, as well as alternative scenarios of upstream withdrawal of freshwater. The findings indicate that climate change will cause significant changes in river salinity in the southwest coastal area of Bangladesh by 2050. These changes are likely to lead to significant shortages of drinking water in the coastal urban areas, scarcity of water for irrigation for dry-season agriculture, and significant changes in the coastal aquatic ecosystems. Changes in the availability of freshwater fish will likely affect the composition of capture fishery, although the increase in brackish water will enhance opportunities for brackish water aquaculture. Assessment of location-specific economic impacts of the changes in river salinity, identification of suitable adaptation alternatives, and costing of adaptation are high priorities for further analysis.

Sea Level Rise and Its Impacts in Coastal Areas of Bangladesh

Sea level rise due to sedimentation, although significant near river deltas, is negligible on a global scale. Sea level rise (SLR) on a short time scale (several years) is associated with El Nino/Southern oscillations. Bangladesh is highly vulnerable to sea level rise, as it is a densely populated coastal country of smooth relief comprising broad and narrow ridges and depressions. A big chunk of the fresh- water zone that will be disappearing due to sea level rise near to the estuary will have a far reaching effect on the country’s ecology and will extinct some of its endangered species. The southwest region of Bangladesh comprises the world’s largest single track of mangrove forest—the Sundarbans, which is also vulnerable to the sea level rise. It is located at the southern extremity of the Ganges river delta bordering the Bay of Bengal. A possible 45 cm sea level rise by the year 2050 could inundate 75 % of the Sundarbans. Several studies are initiated to find out suitable adaptation measures that have the potential to help farmers adapt to climate changes and to identify suitable varieties of crops that would be able to adapt to climate change. One of them is a study titled “Adaptive Crop Agriculture Including Innovative Farming Practices in the Coastal Zone of Bangladesh,” which was conducted in Satkhira, a coastal district of Bangladesh.

Climate Change Impacts, Scenario and Vulnerability of Bangladesh

Bangladesh is affected strongly by climate change. Increasing surface air temperature is most prominent in Bangladesh, where an increasing trend and temporal variation in the mean seasonal temperature is observed within the range of 0.4–0.65 °C during the past 40-year period. Although the winter season experiences the minimum rainfall, historical trend is showing a positive inclination in 27 out of 32 rainfall observatories of the meteorological department. The riverine flood (or monsoon flood) is affected by the following climate change related phenomenon, especially due to change in the frequency and intensity in extreme rainfall event may subsequently increase the intensity of flood. Riverbank erosion is one of the major natural disasters of Bangladesh, which is also related to the monsoon flooding. Floods, especially the high intensity floods, often devastate physical infrastructure such as road networks, educational centres, market places, administrative buildings etc. Changes in climate may affect irrigation requirements for all the three cropping seasons: Rabi, Kharif-I, and Kharif-II. At present, western parts of Bangladesh are periodically being affected by droughts in winter months. Since the temperature will rise, and there exists a strong possibility that the winter precipitation will decrease further, it is likely that the moisture content of topsoil would decrease substantially leading to severe moisture stress.

Urban flooding of Greater Dhaka in a changing climate : building local resilience to disaster risk

Dhaka, the capital of Bangladesh and one of the world’s rapidly growing megacities, is an urban hotspot for climate risks. Preparing for the unfolding impacts of climate-related changes – socio demographic, environmental, economic, and political - is a daunting task. It requires that Dhaka’s policymakers, like those in other megacities of South Asia’s low-lying deltas, understand how climate change is anticipated to affect natural hazards that lead to flooding in the cities. This study’s overall aim is to provide local decision-makers an effective planning approach for minimizing the damage risk of rainfall-induced urban flooding in Dhaka in a changing climate. Specific objectives are to assess the vulnerability of the Greater Dhaka area to urban flooding and waterlogging, estimate probable economic damage due to climate change, develop structural adaptation measures, evaluate the reduction in economic damage resulting from implementing these measures, and estimate their cost. The study comprises four main activities: (a) hydrological modeling and development of adaptation measures, (b) spatial ranking of flood vulnerability, (c) evaluating expected damage from flooding, and (d) estimating adaptation costs. This book is divided into two major parts: study methods (part 1) and results (part 2). Part one is organized into four chapters. Chapter two presents the conceptual framework for the hydrological modeling study and the method and processes used to model future scenarios. Chapter three presents the seven model setups for the detailed study area. Chapter four describes the method used to assess the modeled areas’ relative vulnerability to urban flooding, while chapter five explains the method used to estimate their economic damage. Part two, also organized into four chapters. Chapter six provides the study results for each of the seven modeled areas, while chapter seven summarizes the overall study results for Dhaka city. Chapter eight turns to the secondary flood-mitigation measures that can complement the recommended conveyance-centric solutions. Chapter nine suggests a way forward.

In support of urban adaptation: a participatory assessment process for secondary cities in Vietnam and Bangladesh

Vietnam and Bangladesh are countries already impacted by weather-related extreme events. Scientific modelling projections indicate that climate change, and changes to climate variability, will increase risks for both countries in the future. Targeting this challenging contemporary agenda, this paper reflects on the lessons learned from a collaborative research project, funded by the Asia Pacific Network for Global Change Research, which was carried out jointly in the Vietnamese city of Huế and the Bangladeshi city of Satkhira. The focus on secondary cities was intentional as they face unique challenges – a combination of rapid growth and development, adverse climate-related impacts, and in many cases less institutional adaptive capacity than their primary city counterparts. Whilst numerous assessment tool kits already exist, these have typically been developed for rural or natural resource contexts. Therefore, the objective of this action research activity was to develop a flexible suite of participatory assessment tools and methodologies that were refined specifically for the urban context; as well as being easy to use by local practitioners at the city and neighbourhood scales. This paper summarizes the research and stakeholder engagement activity that was carried out before presenting the main findings from each of the case study cities (detailing both climate-related risks and potential adaptation options). This analysis is further extended to include a reflective critique of the assessment process, a comparative analysis of the activity carried out in the two case studies, and the ‘South–South’ learning process that occurred between project partners. Key findings are then distilled to put forward recommendations in support of climate change assessment activity in secondary cities across the Asia-Pacific region.