The complexity of erosion control stems from several factors that affect erosion but most importantly the results of erosion are evident in loss of fertile topsoil, clogged ditches, culverts and storm sewers that increases flooding, turbid lakes and streams, filled-in ponds, lakes and reservoirs, damage to aquatic habitats and reduced environmental and recreational value and use as well as structural damage to buildings, roads and other structures. It is imperative to categorize the erosion processes and geologic erosion or more commonly known as natural erosion involves the action of wind, water, ice, and gravity and is generally slow and continuous which often goes unnoticed with the exception of some stream and shore erosion. Accelerated erosion is speeding up of erosion owing to human activity which is based on destroying of the natural vegetative cover or alteration of the ground without surface protection provisions. Farming, construction, logging and mining are the principal causes of accelerated erosion. Geologic erosion mostly accounts for less sediment generation relative to accelerated erosion. Accelerated erosion control measures can be used to minimize it through careful planning and implementation of appropriate erosion control solutions. The article seeks to evaluate why we need erosion control solutions based on highlighting the problems followed by describing the various erosion control solutions and mention of why environmentally friendly solutions are preferable from an earth stewardship perspective.
The impact of erosion
There are several reasons why we need erosion control solutions and understanding the impacts of erosion helps in implementing appropriate erosion control solutions. Eroded soil contains nitrogen, phosphorus and other nutrients which when carried into water bodies these nutrients can lead to eutrophication and affect the balance in biological oxygen demand. Erosion of streambanks and adjacent areas destroys streamside vegetation that provides aquatic and wildlife habitats. Down cut stream channels can lower water tables of surrounding floodplain to a depth below the root zones of native plants. Sediment deposited in streams can cover fish spawning gravels, eliminating habitat or smothering developing eggs. Sediments in streams can smother the bottom fauna, affecting the food web. Turbidity from sediment reduces in-stream photosynthesis, which leads to reduced food supply and habitat, turbidity increases amount of sunlight absorbed in water, raising stream temperatures. Erosion removes topsoil which is the biologically active strata of soil that supports plant life and erosion also leaves scars of infertile mineral soil in the landscape which reduces its aesthetic value and slower revegetation. All these are environmental impacts of erosion and we will now focus on more economic impacts of erosion.
Quantification of economic impacts is multifaceted because it is challenging to assign a monetary value to loss of aquatic habitat or poor aesthetics which is unlike a silted up reservoir for example. Economically, the impacts of erosion include excessive sediment accumulation which reduces reservoir storage capacity and hence more frequent and consistent sediment removal is required. The cost of building new reservoirs to replace lost reservoir capacity is high and increasing land values and lack of available sites make the feasibility complex. Nutrients carried in sediment can feed algal blooms which excrete toxins that are not easily removed from drinking water sources and the chemical processes of removing these toxins is costly and the downside of algal blooms in resort waters for example negatively affects tourism and recreational economies. Sediment deposited into streams reduces flow capacity which interferes with navigation and increases the risks of flooding which also means that regular maintenance is required which is a costly process. Erosion severely destroys the ability of soil to support plant life and restoration is a very costly process. In the construction business, time spent cleaning up sediment, repairing and replacing neglected best management practices removes staff from construction activities which often affects schedules and budgets. The non-conformities to erosion related legislation can lead significant violations which can result in facing the wrath of the law through fines.
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Risk management
The principles of effective erosion control require first that the soil surface be protected from the erosive forces to prevent erosion, and secondly the eroded sediment be captured at the source. By definition erosion control is the prevention of soil erosion whereas the complementary sediment control is the trapping of suspended soil particles. We will now highlight the erosion control solutions which begin in erosion control plan where it is important to review and consider all existing condition in the initial site selection of the project. For example if site construction is fit to the terrain little grading is necessary and erosion potential is consequently reduced therefore timing of grading and construction is key to minimize soil exposure. Scheduling whilst taking into account season and weather forecast is vital which also works in stabilizing disturbed areas as quickly as possible and if possible preference for dry seasons over wet seasons although in wet seasons additional erosion control measures can be implemented.
Retention of existing vegetation whenever feasible is paramount because vegetative cover is an effective form of erosion control solution as minimal erosion occurs on a soil covered with undisturbed natural vegetation and integration of existing trees and natural vegetation into the site improvement plan is imperative. Newly planted vegetation begins to duplicate the functions of established vegetation hence it is important to vegetate and mulch denuded areas as mulch helps seedlings to become established and protects the soil from raindrop splash until vegetation takes over. Management and control of runoff in areas that have been denuded with rerouting runoff into stabilized channels. Covering of exposed soils with rolled erosion control products, mulch, compost blankets or hydraulically applied matting will protect soils and provide immediate protection which is not limited by seed germination and plant establishment to provide cover. Since slope length and steepness are amongst the most critical factors in determining erosion risk minimizing them decreases the velocity of runoff which ultimately reduces erosive energy. In anticipation of concentrated or increased runoff it is also key to prepare drainage ways and outlets. Surely it is important to implement erosion control solutions but to make them effective inspection and maintenance are critical to function of the erosion control solutions.
Best practice
The key take-home from the problems and solutions is the importance of controlling erosion at the source which if performed using environmentally friendly means contributes further to earth stewardship. Preference for environmentally friendly solutions is core to Global Road Technology’s erosion control solutions and one such innovative environmentally friendly solution is GRT Enviro-Binder. Combining polymer technology and the need for controlling erosion at the source, the polymer binds and agglomerates fugitive soil particles creating a sacrificial crust which protects the underlying layers from any form of deposition or transport to create sediments. The life cycle of GRT Enviro-Binder is considered at formulation that factors in the importance of biodegradability with products that are not harmful to the environment. In essence the erosion control solution offered by GRT tackles the problem of erosion with thought of what happens post its service life which resonates with offering green solutions without compromise on how effective they are at controlling erosion at the source.
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REFERENCES.
Mikula, D., and Croskey, H. 2005. Soil Erosion and Sedimentation Control Training Manual. Michigan Department of Environmental Quality.
Oregon Department of Transport. 2019. Erosion Control Manual: Guidelines for Developing and Implementing Erosion and Sediment Controls.
Rivas, T. 2006. Erosion Control Treatment Selection Guide. United States Department of Agriculture.
