Mapping Mangrove Opportunities with Open Access Data: A Case Study for Bangladesh

Abstract

Mangroves protect coastal areas against hazards like storms or cyclones by attenuating waves and currents, and by trapping floating debris during extreme events. Bangladesh is a very vulnerable country to floods and cyclones, and part of its coastal system is thus being upgraded to a higher safety standard. These upgrades include embankment reinforcement and mangrove afforestation schemes seawards of the embankments. To further strengthen the implementation of combined green–grey infrastructure in future programs, identifying potential mangrove development sites near the polder systems is a necessary first step. We thus developed a tool to systematically identify mangrove sites throughout the coastal area based on open access data. This method identifies potential sites for mangrove development based on their distance from existing mangrove patches and suggests the required technique to implement the vegetation depending on the rate of coastline change. Our method showed that approximately 600 km of the coastal stretches placed seawards of embankments are within 10 km of existing mangroves, and could thus be potential sites for mangrove establishment. Out of those 600 km, we identified 140 km of coastline where the landwards polders are particularly vulnerable to flooding. The sites with highest restoration potential and priority are located in Galachipa, Hatiya, Bhola, Manpura, Khangona, and Boro Moheshkhali. More detailed data collection and local assessments are recommended prior to executing mangrove afforestation schemes. Nevertheless, this method could serve as a useful systematic tool for feasibility studies that identify mangrove opportunities in data-scarce areas and help to prioritize data collection at the sites of highest interest.

Quantitative Analysis of Methodological and Environmental Influences on Survival of Planted Mangroves in Restoration and Afforestation

“…Here, again, the wider spacings used in plantings of species such as Sonneratia spp. probably reflect specific applications of afforestation for rapidly accreting sediments in places such as Bangladesh [50], reflecting a desire to cover as extensive an area as possible to protect vulnerable coastlines from flooding and cyclones [51].…”

Wave Reduction by Mangroves during Cyclones in Bangladesh: Implementing Nature-Based Solutions for Coastal Resilience

“…Potential sites for mangrove establishment have been mapped in Bangladesh (Gijón Mancheño et al, 2021), indicating locations where mangroves could grow naturally, and those where erosion mitigation would be necessary for mangrove colonization. However, the potential wave load reduction by mangroves at such sites has not been investigated, which hinders accounting for the effect of mangroves on embankment designs in future CEIP programs.…”

“…Surge heights often reach 3-5 m (Karim and Mimura, 2008;Zaman and Mondal, 2020), and observations suggest that 10 m water levels (consisting of surge plus tides) occur with a frequency of once in every 20 years (Dasgupta et al, 2014). 11 Several potential sites for mangrove afforestation seaward from dikes have been identified in the coastal system of Bangladesh (Gijón Mancheño et al, 2021), which are shown in Figure 3.1. These afforestation sites were selected considering several criteria:…”

“…Mangrove belts could also provide additional protection to coastal structures by attenuating short waves, and thus reducing the wave loads acting on them and the wave runup. Potential locations for mangrove afforestation seaward from embankments have been identified for Bangladesh (Gijón Mancheño et al, 2021), however, their effect on the wave loads acting on the structures and on wave runup has not been evaluated. This paper quantifies the potential wave height reduction by a mangrove belt planted on the seaside of embankments, and how such wave attenuation would impact embankment designs.…”

Environmental impact of submerged and emerged breakwaters

“…Various coastal protection measures are available, including soft and hard measures. The soft solutions often involve non-structural techniques, such as beach nourishment ( Pinto et al., 2020 ), vegetation cover ( Gomez et al., 2020 ), and mangrove afforestation ( Gijón Mancheño et al., 2021 ). On the other hand, the hard options are related to structures that do not develop naturally, such as rocks, concrete, steel, or timber ( Siegel, 2020 ).…”