Md Ataul Gani earns PhD for research that paves way for sustainable river dredging
On 7 October, Md Ataul Gani from Bangladesh defended his PhD thesis on the impact of changes in river morphology on nitrogen retention and retention processes. Professor Ken Irvine and Professor Michael McClain are his promotors and Dr. Gretchen Gettel and Dr. Hans van der Kwast his co-promotors. Dr. Md Ataul Gani, who was awarded a doctoral degree for his research, shared a few insights as he embarks on a new chapter of his life.
My research aims to contribute to more sustainable dredging in river systems in tropical countries. Large lowland tropical rivers change their flow and shape – their morphology. This is mostly due to natural seasonal discharge variations, but human activities can also change the river morphology. Sediment extraction due to dredging, river bank management programmes and other human activities can alter the water flow path and sediment distribution in the river. This affects the way the river transports nutrients – thereby also the river health, and in the end, coastal ecosystems.
Our study suggests that the alternation of river geomorphology due to human activities should be limited – this would help tackle the problem of river health associated with nutrient retention and export.
If rivers retain nutrients instead of transporting them downstream, the amount of nutrients that end up coastal areas is reduced. This has benefits: too much nutrients in coastal areas cause hypoxia and eutrophication, which decreases water quality and harms aquatic life and the coastal ecosystem. In my PhD research, I studied how different geomorphic units (GUs) of the Padma River in Bangladesh affect nitrogen retention.
Dredging and other human activities can modify a river’s GUs, thereby significantly altering nitrogen transport to the coastal areas. Our study suggests that the alternation of river geomorphology due to human activities should be limited – this would help tackle the problem of river health associated with nutrient retention and export.
Data + a satellite-based model
I will always remember when I worked with one of my co-promoters in the field and laboratory in Bangladesh. During sample collection, we used to discuss how we could use this data to develop a satellite-based model. This inspired and encouraged me to stick to my plan during data analysis, although it took a lot of time. The most challenging part of my PhD studies was field samplings and lab analysis during COVID-19.
Knowledge gap
There is a considerable knowledge gap in how to implement dredging projects in a way that considers river health. River engineers often suggest dredging floodplain rivers to continue river flow and to protect against floods. However, they often fail to consider the impact of removing river bars: this can increase nutrient pollution in the downstream estuaries and even on the coast. Sustainable dredging work can be done to manage rivers in a way that minimizes the influence on river geomorphology and nitrogen retention and export mechanisms.
Delta Plan 2100 in Bangladesh
In the next few years, I will try to be involved in projects that can create scope for further research based on my PhD research. At the same time, I will try to highlight my research findings in Bangladesh. One of the aspects of Delta Plan 2100 in Bangladesh is implementing dredging to manage the river flow, preventing bank erosion and floods.
Keep it simple
Initially, I was used to thinking big about my research: considering lots of work with different directions. Now, I realise that I should keep it simple and focus on in-depth work. The simpler, the better it is applicable in the real world.
Thesis title and summary
The title of his thesis is: Nitrogen Retention in Different Geomorphic Units of a Large Lowland River
Large lowland rivers are geomorphologically diverse, with variations in flow that influence nitrogen retention. Nitrogen retention is a valuable ecosystem service protecting the downstream aquatic ecosystem from eutrophication. The research focuses on nitrogen retention in distinct geomorphic units of the large lowland Padma River in Bangladesh. Sentinel-2 imagery (2019-2020) was processed using NDVI values to classify geomorphic units (GUs) and map nutrient-retention/export-relevant geomorphic units (NREGUs) of the study area, which showed seasonal discharge variations were responsible for changes in the surface area and a number of GUs. The field measurements of potential denitrification rate (PDR) were performed to show the spatiotemporal distribution of PDR using different linear mixed models (LMMs), including Sentinel-2 band 11 and NDVI, and the application of the best-performed LMM showed that the number and surface area of GUs were responsible for the alteration of PDR in the study reach. Monthly field investigations employing the mass balance approach provide an integrated value of nitrogen retention of the study reach. This enables comparison with the retention processes in the reach, such as nitrogen loss due to water retention, sedimentation and net PDR. The present study showed that the alteration of GUs can regulate these retention processes, thus revealing the effect of river management programmes on river health and ecology.