Coupled Adaptive Cycles of Shoreline Change and Households in Deltaic Bangladesh: Analysis of a 30-Year Shoreline Change Record and Recent Population Impacts

Abstract

This research investigates the spatiotemporal dynamics of shoreline change and associated population impacts in deltaic Bangladesh. This region is among the world’s most dynamic deltas due to monsoon precipitation that drives tremendous discharge and sediment volumes from the Ganges–Brahmaputra–Meghna drainage basin. Theoretically, it draws on the concept of adaptive cycles that theorizes systems transitioning through phases of growth, conservation, release (collapse), and reorganization, with a focus on the cycle’s release (collapse) phase and coupled linkages between the natural system of shoreline change and social system of household behavior. We use Landsat imagery to produce and describe a thirty-year record of shoreline change for an 80-km stretch of the Lower Meghna estuary. Household survey data characterized population impacts and risk perception for a subregion with high erosion rates. Results identified significant space–time differences and patterns of shoreline change and population impacts consistent with the adaptive cycle. North, central, and south regions exhibited statistically significant differences in space–time patterns of shoreline change. Substantial numbers of households reported displacement due to riverbank erosion and high levels of experience and worry about future displacement. Results demonstrate how geospatial analysis of a multidecade record of shoreline change along with analysis of household survey data can identify regions most vulnerable to riverbank erosion with implications to inform mitigation and adaptation. This work adds empirical demonstration of coupled adaptive cycles to the literature. Limitations and complexities of the adaptive cycle framework are discussed.

本文研究孟加拉三角洲地区海岸线的时空变化及其对人口的影响。季风降雨导致的大量来自恒河-布拉马普特拉河-梅克纳河流域的径流和沉积, 使得该区域是世界上变化最频繁的三角洲。理论上, 对具有增长、保留、释放（收缩）、重组等阶段的系统, 适应性循环概念可以提供理论基础, 并耦合循环释放（收缩）阶段、海岸线变化自然系统和家庭行为社会系统。我们利用Landsat影像, 制作和描述了长达80公里的下梅克纳河口30年海岸线变化。通过家庭调查数据, 本文描述了局部高侵蚀率地区的人口影响和灾害观念。研究确认了显著的时空差异, 以及与适应性循环相吻合的海岸线变化模式和人口影响。北部、中部和南部区域在海岸线变化的时空模式上存在着统计上的显著差异。很多家庭因河岸侵蚀而迁移, 也对未来的搬迁表达了很大忧虑。对数十年海岸线变化数据的空间分析和家庭调查数据的分析, 可以确定河岸侵蚀最脆弱区域, 为减灾和适应提供信息。本研究提供了耦合适应性循环的经验证明, 也讨论了适应性循环框架的局限性和复杂性。

Esta investigación indaga sobre la dinámica espaciotemporal de cambios en el litoral y los impactos asociados sobre la población en el Bangladesh deltaico. Esta región figura entre los deltas más dinámicos del mundo debido a la precipitación monzónica que se traducen en una descarga tremenda y grandes volúmenes de sedimentos dentro de la cuenca de drenaje de los ríos Ganges–Brahmaputra–Meghna. Desde el punto de vista teórico, la investigación se apoya en el concepto de ciclos adaptativos, el cual teoriza los sistemas en función transicional a través de las fases de crecimiento, conservación, liberación (colapso) y reorganización, con focalización en la fase de liberación (colapso) del ciclo y los vínculos acoplados entre el sistema natural del cambio del litoral y el sistema social de la conducta de la familia. Usamos imaginería Landsat para producir y describir un registro del cambio del litoral de treinta años para un trecho de 80 km en el estuario del Bajo Meghna. Los datos del estudio de hogares caracterizaron los impactos sobre la población y la percepción del riesgo para una subregión con altas tasas de erosión. Los resultados identificaron diferencias y patrones significativos de espacio–tiempo en los cambios del litoral e impactos sobre la población que tienen consistencia con el ciclo adaptativo. Las regiones del norte, centro y sur exhibieron diferencias estadísticamente significativas en los patrones de espacio–tiempo del cambio del litoral. En un número sustancial de hogares se reportó desplazamiento asociado con la erosión de los bancos del río y con altos niveles de experiencia y preocupación acerca de desplazamientos futuros. Los resultados demuestran cómo el análisis geoespacial de un registro multidecadal de cambio del litoral, junto con el análisis de los datos del estudio de hogares, pueden identificar las regiones más vulnerables a la erosión de los bancos ribereños con implicaciones para informar la mitigación y la adaptación. Este trabajo agrega para la literatura demostración empírica de ciclos adaptativos acoplados. Se discuten las limitaciones y complejidades del marco del ciclo adaptativo.

Key Words:

• adaptive cycle
• erosion/accretion
• household survey
• remote sensing
• spatiotemporal analysis

关键词:

• 适应性循环
• 侵蚀/加积
• 家庭调查
• 遥感
• 时空分析

Palabras clave:

• análisis espaciotemporal
• ciclo adaptativo
• erosión/acreción
• estudio de hogares
• percepción remota

Acknowledgments

We thank the anonymous reviewers from the Annals of the American Association of Geographers for suggestions and Dr. Ahmed Salahuddin for his contributions during preliminary work informing this research.

Additional information

Funding

This research was supported by grants from the U.S. National Science Foundation (#1660447) and the Asia-Pacific Network for Global Change Research (#ARCP2012-23NSG-CRAWFORD).

Notes on contributors

Thomas W. Crawford

THOMAS W. CRAWFORD is a Professor in the Department of Geography at Virginia Polytechnic Institute and State University, Blacksburg, VA 24061. E-mail: [email protected]. His research interests include coastal hazards, vulnerability, and resilience and geospatial applications.

Munshi Khaledur Rahman

MUNSHI KHALEDUR RAHMAN is an Assistant Professor in the Department of Geology and Geography at Georgia Southern University, Statesboro, GA 30458. E-mail: [email protected]. His research interests include the study of nature–society interactions, vulnerability and resilience, application of geospatial technologies, and spatial analysis.

Md. Giashuddin Miah

MD. GIASHUDDIN MIAH is a Professor in the Department of Agroforestry and Environment and currently is the Vice Chancellor of the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh. E-mail: [email protected]. His research interests include climate change, land use, ecosystem management, resource use in agroforestry, livelihoods, and food security.

Md. Rafiqul Islam

MD. RAFIQUL ISLAM is a Professor in the Department of Agronomy at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh. E-mail: [email protected]. His research interests include natural resource management, geospatial analysis and climate-smart agriculture, agro-ecosystem management, and livelihood development of the rural community.

Bimal Kanti Paul

BIMAL KANTI PAUL is a Professor in the Department of Geography and Geospatial Sciences at Kansas State University, Manhattan, KS 66506. E-mail: [email protected]. His research interests include human–environment interactions, population and health geographies, and global climate change.

Scott Curtis

SCOTT CURTIS is a Distinguished Professor of Natural Sciences and Mathematics in the Department of Geography, Planning, and Environment at East Carolina University, Greenville, NC 27858. E-mail: [email protected]. His research seeks to understand how water hazards and hydroclimatic variability and change affect society.

Md. Sariful Islam

MD. SARIFUL ISLAM is a PhD Candidate in the Geospatial and Environmental Analysis Program in the Department of Geography at Virginia Tech, Blacksburg, VA 24061. E-mail: [email protected]. His research interests include coastal hazards, remote sensing and GIS, and human–environment interactions.