ALLUVIAL_FANS and their carbon sequestration.pptx

about alluvial fans

1. ALLUVIAL FANS Carbon Sequestration Potential of Megafans in India

2. What are Alluvial fans? A triangle shaped buildup of sediment from a river or stream that flows onto a flat plain. They can range from a few hundred metres to hundreds of kilometres.

3. Process of formation 1. Erosion and Sediment transport Source of Sediment Sediment Transport 2. Deposition at the Fan Apex Sudden decrease in gradient Initial sediment deposition 3. Spreading of Sediment Radial deposition Channel Migration 4. Fan development and Slope Maintenance Growth of fan Slope stability 5. Vegetation and Soil Development Growth of vegetation Soil Formation 6. Mature Alluvial fan Fully Developed fan Dynamic changes

4. Narmada Alluvial Fan

5. Narmada Alluvial Fan

6. The dominance of debris-flow deposits indicates that the Narmada fan formed under the semi-arid conditions that prevailed during the Pleistocene. The erosion of the alluvial fan was due to a major episode of tectonic re-activation of preexisting lineaments. This led to the re-confinement of the feeder channel, which prevents fan aggradation in spite of high discharges. While tectonics was responsible for providing the basin depression and the geomorphic contrast necessary for flow expansion, climate controlled the debris-flow, sheet-flow and stream-flow that built the alluvial architecture of the fan.

7. Kosi Alluvial Fans Width = 115km Length=150km

8. Tectonic Influence on Fan Morphology Himalayan Frontal Thrust (HFT) and Transverse Faults: The study found that ongoing tectonic activities along the HFT and transverse faults have controlled the morphology and aggradation processes of the alluvial fans. These tectonic movements have caused differential subsidence, channel migration, and shifts in depocenters. Tilting and Uplift: The study identified tilting of the fans, uplift of the proximal parts, and the development of gravel ridges and terraces, which are linked to tectonic activity along these faults.

9. Which factors influence avulsion of Kosi River? 2. How is the Megafan impacted by tectonic thrusts? 3. What is the Carbon Sequestration Potential of the Megafan? 4. Stability of the sequestered carbon over centuries? QUESTIONS