Silt is created when rocks are eroded or worn away by wind or water. Silt is made up of tiny rock and mineral particles that are smaller than sand. It can be transported by water, wind, ice and deposited. As silt flows along it chips more rocks.. Silt is found in soil along with other types of sediments like gravel and clay. The soil can be classified as silt if it has 80% of silt. Silt settles in water and gets deposited in lakes, ponds and wetlands.
Environmental Impact
Increases the risk of flooding: As silt accumulates, it does not allow groundwater recharging. The capacity of the lake/pond reduces, thus leading to flood when there is heavy rainfall.
Loss of fish and wildlife: The oxygen level in the water reduces thus not suitable for aquatic life to survive. It often creates an acidic condition, reducing the quality of water.
Dense algae and bad odor: Stagnant water gives an unpleasant smell and the high nutrient levels of silt encourages algae blooms. In summers, the water body gets warmer resulting in an increased growth of algae and weeds.
Silt can also change the landscape of where it deposits. Where there are less or no trees, deposits of silt can harm the ecosystem. Fertilizers, chemicals and industrial waste can runoff along with silt and become toxic. Toxic silt is harmful for the river, lake and pond. It affects plants, vegetation, aquatic life and contaminates the water.
Fertile Soil
Silt is light and fertile for growing crops, it promotes water retention and air circulation. Silty soil is rich in nutrients, also easily cultivable. Silty soil supports diverse growth of plants and crops. Silt deposits are used for agriculture, they provide high yields.
Lotus plant blooms above water but takes its roots in silty, muddy wet soil.
Many organisms live and survive in silt. Frogs hibernate during winter in silt at the bottom of a lake or pond. This is because water does not freeze/ get cold at the bottom this provides some insulation or warmth.
Silt Traps
Silt impacts the freshwater ecosystem and aquatic life. It controls the flow of silt by having barriers.
Silt traps – Silt traps are structures made of boulders, they trap silt. They are built alongside drainage ways of water. They reduce the accumulation of silt in the lake bed.
Silt Fence – Silt fence is used to catch the sediments/silt that runoff. Silt fences are made up of wire and fabric. This is used in construction sites to restrict the flow of contaminated water to nearby areas. Silt fence is also called a filter fence. It controls the silt and sediment flow into rivers, lakes and ponds. It should be installed alongside the contour of the slope.
Reference: silt | National Geographic Society
Lakes of India 