Influence of surface geology and micro-scale land use on the shallow subsurface salinity in deltaic coastal areas: a case from southwest Bangladesh

A K M M Rahman,A P Butler,M A Hoque,K M Ahmed

doi:10.1007/s12665-018-7594-0

Abstract

Salinity, both in soil and water, is a ubiquitous problem in coastal Bangladesh, particularly in the southwest. Salinity varies at the local scale (5–10 m), but the relative roles of land use and surface geology on salinity variation in near-surface (< 5 m) groundwater are not fully understood. Surface geology, land use and salinity in near-surface (ca. 3 m) groundwater at two small sites (each 0.05 km2) were explored in the southwest coastal region of Bangladesh. The sediments in the near-surface at both sites are fine and hydrometer analyses of cored samples indicate the dominance of silty clay (70%) along with very fine sand (5%), sandy clay (15%) and clay (10%) materials. Salinity variation in near-surface groundwater tends to follow land use rather than surface geology at the scale of our investigations. The study provides evidence of the influence of land use on the near-surface salinity variation and indicates the importance of land-use planning in salinity management in coastal areas.

Highlights

Coastal areas are one of the most productive regions in the world where millions of people live and produce agricultural goods (Glantz 1992)
Agriculture, mostly rice farming, is the main source of income for the population living in these reclaimed lands
Land use is characterised by agricultural land inside the polders, while outside the polder shrimp farming is dominant (Fig. 1)

Summary

Introduction

Coastal areas are one of the most productive regions in the world where millions of people live and produce agricultural goods (Glantz 1992). Recent storm surges associated with these cyclones, such as Sidr in 2007 and Aila in 2009, have left a trail of destruction and inundated large areas with sea water in the southwest coastal region of Bangladesh (Kibria et al 2015). These inundations have resulted in widespread salinity problems in the area, including high soil salinities, which have led to a reduction in agricultural yield (Dasgupta et al 2015). Future rising sea levels coupled with embanked landscape and reduced up-stream flow (Mirza 1998) will most likely increase the area of inundation from similar surges (Bhuiyan and Dutta 2012; Dasgupta et al 2009; Karim and Mimura 2008; Singh 2002)

Methods

Results

Conclusion