Role of river sediments
Dr. Vipulab Sharma
Flowing water, depending upon the size is known by different names as brook, stream or river. Rivers constitute the life line system of any region. Without rivers life is not possible to exist. All the ancient as well as modern civilisations flourished along the river side. According to Hindu mythology, the rivers are considered sacred and next to God.
In the countryside or in cities, the sight of clean, calm and flowing water has an instantly mesmerising effect on our minds. Beginning from the place in the uplands, at the point of origin, it flows through the plains, catering the needs of living beings and ends its life ultimately meeting the sea. Besides being indispensible in our lives, we only know a much bit of such an important ecosystem.
A river actually constitutes not only water but other components also. River is a complete unit consisting of water, living organisms as well as sediments. Let’s take a trip around the river to know the sediments.
Technically speaking, sediments are the loose sand, silt, clay and other particles carried by each of the natural agents (such as water, wind and ice, released due to volcanic eruption, weathering etc.) and anthropogenic activities (such as runoff from land or direct discharges) to lakes, streams and rivers, that settle at the bottom of the water body. But for a common man, sediments are nothing more than the mud deposited along the river side. While travelling from uplands to plains, rivers carry numerous materials with them that are ultimately deposited as sediments in the plains. This deposited material play an outstanding role in limnological studies as they can both reflect and affect what is occurring in the overlying waters. Besides, being a natural buffer system, they provide an important habitat for aquatic organisms that either dwell on or in the sediments. Sediments are an important medium to estimate the degree and history of chemical contamination of environmental regimes and are also helpful in the transfer of nutrients to the biota. Sediment is important because it often enriches the soil with nutrients. Areas rich in sediments are often also rich in biodiversity. Sedimentary soil is usually better for farming. Deltas and river banks, where much sediment is deposited, are often the most fertile agricultural areas in a region. Unfortunately, the most important part of the system is the most ignored one.
Because of their variable physical and chemical properties, they not only act as source and sink of nutrients in an aquatic system, but also provide a record of river’s pollution history. Due to unfortunate modernization, the wastes from the different sources like household, industries and agriculture is blindly flushed out in the rivers.
But nobody bothers where it ultimately goes? It goes nowhere but is usually deposited at the river bed sediments or on the riverside sediments. In the due course of time, these pollutants undergo decomposition and release toxic nutrients thereby polluting the overlying waters and poisoning the aquatic flora and fauna.
So we must awake in time so that this important system of the rivers can be preserved and conserved. There are certain DO’s and DON’Ts for conservation:
Sediments are affected by:
o the removal of vegetation on erodible soils, leaving them exposed;
o soil disturbance and clearing adjacent to the shoreline;
o filling with foreign soils;
o roads within 200 feet of the shoreline;
o high road density or impervious surface in the basin;
o shoreline armoring;
o channelisation of streams;
o increase in stream flows.
In order to effectively manage sediment a greater understanding and appreciation of the complexity of sediment balances, scales of operation and key principles requires development, including the recognition that:
* Sediment varies spatially and
temporally in supply, transport and deposition.
* Natural and anthropogenic systems which are intricately interwoven can be affected by alterations in the delicate balance of sediment quality and
* Effective sediment management must be site specific and therefore be considered for the processes controlling sediment transport and deposition.
* Sediment management must consider the sediment balance and its role in the hydrological and hydraulic processes within each river.
* Unrestricted extraction of the sediments should be checked as the negative consequences such activities on plethora of the system cannot be ignored.
* Local masses should be equally involved in conserving and preserving this natural stratum of rivers.