Overview
This research note highlights the importance of developing a UDA Framework for Sedimentation Management. It suggests that Sedimentation Management is a large-scale multilevel problem and requires cooperation from different stakeholders to avoid fragmented approach and formation of policy. Further, it provides various methods for application of Sedimentation Management such as Water resource management, Port management, Inland Water Management and Ecosystem Management. It recommends employing an effective and integrated system of sediment management in every water based project in the country.
Key highlights
- India has 5,202 large dams and many more small dams and barrages, 111 inland waterways classified as ‘National Waterways’ (NWs) having 20,275 kms spread across 24 States and a coastline of total length 7516.6 km including mainland, Lakshadweep islands and Andaman.
- There is high flow of water bodies due to concentration of annual monsoon in one quarter of the year causing excessive siltation. Thus, sediment deposition threatens the sustainability from both onsite and off site damages causing enormous costs to the national economy.
Application of Sediment Management
- Water resource Management: Loss of reservoir storage results in reducing flexibility in generation and makes the hydropower plant dependent on seasonal flows.
- Port Management: India faces huge longshore sediment movement along the eastern coast by wave action. During the past few years, due to deepening of harbor channels for expansion, siltation and coastal erosion has become more severe.
- Inland Water Transport: Shifting of river courses, channel logging in agricultural land & infrastructural areas along the floodplain poses difficulty in navigation.
- Ecosystem Management: Accumulation of sediment in reservoirs adversely changes ecology and affects fish and other species by covering spawn sites, reducing water clarity to visual feeding animals and destroying benthic food resources
Sediment extraction
- Dredging: Debris and unwanted sediments are pumped out by Dredge which creates a vacuum for suction.
- Controlled sediment flushing: In flushing, the flow is used to remove any previously deposited reservoir sediments or a heavy sediment concentrated flow is passed through the reservoir during high flow.
- Sediment extraction from canals through settling basins: Principle is to significantly reduce the velocity by increasing width & depth forcing the sediment to deposit.
- Vortex chamber extractors: Sediment is removed through vortex flow where high tangential velocity enters through the central orifice of the cylindrical chamber. A sediment concentration gradient is created across the vortex.
Challenges
- The maintenance of harbour entrances through dredging is an expensive investment in maritime administration and one of the major problems encountered by ports in India.
- Lack of proper dumping sites poses a big problem in sediment disposal.
- Other aspects which need to be addressed range from Policy issues to technology gap and capacity & capability building requirement.
- There has been a lack of understanding of underwater medium due to random behaviour and underwater channel fluctuations.
Key recommendations
- There is a need for stakeholder fragmentation and involvement at each level.
- The recommended stakeholders range from Policy experts to policy makers and citizens.
- Each stakeholder is required to enrich the process by providing his share of ideas and solutions which increases the support for the proposed policy.
- Precise sediment classification can facilitate effective desiltation and can also help in preventing further siltation by providing deeper understanding of the siltation process.
- There is a need for development of a comprehensive database management system and application & site specific measurements
“It is extremely important to employ an effective and integrated system of sediment management in every water-based project in the country.”
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