SOIL DEGRADATION IN OUR NEIGHBOURHOOD-BY TEAM RAINBOW

ENVIRONMENTAL MANAGEMENT

 

SOIL DEGRADATION IN OUR NEIGHBOURHOOD

            RAINBOW

                                                                                                                                                                                                                                    Akhila K S

                                                                   Geethu  Gopal

                                                                                                                                          Saima  K R

IMK Senate House Campus, Palayam

Soil degradation means When plants (trees & shrubs) are cleared from a site, soil is exposed to sunlight and the eroding effects of wind and water. Soil aeration is increased and the rate of weathering increases.Apart from erosion, the proportion of organic matter in the soil gradually decreases, through the action of microbes in the soil which use it as a source of energy ‑ unless the new land use provides some replacement

TYPES OF SOIL DEGRADATION

A number of major soil related problems occur include:

  • Loss of soil fertility (see lesson on nutrition)
  • Erosion
  • Salinity
  • Soil compaction
  • Soil acidification
  • Build up of dangerous chemicals.

Now we consider the soil degradation in our neighbourhood- Neyyattinkara Municipality.

first we will give a brief history about our  place neyyattinkara

Neyyattinkara is municipality in Thiruvananthapuram district in the Indian state of Kerala. The name Neyyattinkara in Malayalam literally means the shore (kara) of Neyyar River. Neyyar River flows from Agasthyarkoodam , the highest peak (1868m above MSL) in southern end of the Western Ghats. The taluk has a total population of 858,991 with 88.6% classified as rural. Most of the urban population lies within the municipality area which is densely occupied.

The municipality of Neyyattinkara is the major town on the banks of Neyyar River. Neyyattinkara lies 18 km to the south of Thiruvananthapuram city on the National Highway 47 to Kanyakumari. The rapidly growing Thiruvananthapuram city has almost reached its outskirts. Aruvippuram, the holy land of Sree Narayana Guru is an important pilgrim centre near Neyyattinkara. Neyyar Dam is another popular picnic spot near Neyyattinkara at Kallikkadu panchayath of Neyyattinkara Taluk. Neyyattinkara and the neighbouring areas has many cottage industries and handloom. The Balaramapuram Handloom Industry is known worldwide for its fine hosiery.

The main large scale manufacturing industry is the Kerala Automobiles Ltd. at Aralummoodu. It is a much sought after brand in the developing ASEAN nations for good quality three-wheelers.[1]

Agasthyarkoodam, the highest peak in southern kerala is located in Neyyattinkara taluk. It is a pilgrim spot and popular trekking place. The mountain got its name from sage Agasthyar who is considered one of the seven Rishis (Saptarishi) of Hindu mythology. A statue of Agasthyar stands on top of the peak where the devotees can render their prayers. The mountain forms a part of the Agasthyarkoodam biosphere reserve which is home to many endemic flora and fauna.

Now a days our place facing lot of environmental problem like soil degradation, soil pollution and land degradation. The photos of some of the problems are given below

Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts,radioactive materials, or disease causing agents, which have adverse effects on plant growth and animalhealth.Soil is the thin layer of organic and inorganic materials that covers the Earth’s rocky surface.

The organic portion, which is derived from the decayed remains of plants and animals, is concentrated in the dark uppermost topsoil. The inorganic portion made up of rock fragments, was formed over thousands of years by physical and chemical weathering of bedrock. Productive soils are necessary for

agriculture to supply the world with sufficient food.

There are many different ways that soil can become polluted, such as:

• Seepage from a landfill

• Discharge of industrial waste into the soil

• Percolation of contaminated water into the soil

• Rupture of underground storage tanks

• Excess application of pesticides, herbicides or fertilizer

• Solid waste seepage

The most common chemicals involved in causing soil pollution are:

• Petroleum hydrocarbons

• Heavy metals

• Pesticides

• Solvents

Types of Soil Pollution

• Agricultural Soil Pollution

i) pollution of surface soil

ii) pollution of underground soil

• Soil pollution by industrial effluents and solid wastes

i) pollution of surface soil

ii) disturbances in soil profile

• Pollution due to urban activities

i) pollution of surface soil

ii) pollution of underground soil

Causes of Soil Pollution

Soil pollution is caused by the presence of man-made chemicals or other alteration in the naturalsoil environment. This type of contamination typically arises from the rupture of underground storagelinks, application of pesticides, percolation of contaminated surface water to subsurface strata, oil and fuel dumping, leaching of wastes from landfills or direct discharge of industrial wastes to the soil. Themost common chemicals involved are petroleum hydrocarbons, solvents, pesticides, lead and otherheavy metals. This occurrence of this phenomenon is correlated with the degree of industrialization andintensities of chemical usage.A soil pollutant is any factor which deteriorates the quality, texture and mineral content of thesoil or which disturbs the biological balance of the organisms in the soil. Pollution in soil has adverseeffect on plant growth.Pollution in soil is associated with

• Indiscriminate use of fertilizers

• Indiscriminate use of pesticides, insecticides and herbicides

• Dumping of large quantities of solid waste

• Deforestation and soil erosion

Indiscriminate use of fertilizers

  Soil nutrients are important for plant growth and development. Plants obtain carbon, hydrogen and oxygen from air and water. But other necessary nutrients like nitrogen, phosphorus, potassium, calcium, magnesium, sulfur and more must be obtained from the soil. Farmers generally use fertilizers to correct soil deficiencies. Fertilizers contaminate the soil with impurities, which come from the raw materials used for their manufacture. Mixed fertilizers often contain ammonium nitrate (NH4NO3), phosphorus as P2O5, and potassium as K2O. For instance, As, Pb and Cd present in traces in rock phosphate mineral get transferred to super phosphate fertilizer. Since the metals are not degradable, their accumulation in the soil above their toxic levels due to excessive use of phosphate fertilizers, becomes an indestructible poison for crops. The over use of NPK fertilizers reduce quantity of vegetables and crops grown on soil over the years. It also reduces the protein content of wheat, maize, grams, etc., grown on that soil. The carbohydrate quality of such crops also gets degraded. Excess potassium content in soil decreases Vitamin C and carotene content in vegetables and fruits. The vegetables and fruits grown on overfertilized soil are more prone to attacks by insects and disease. Indiscriminate use of pesticides, insecticides and herbicides

Plants on which we depend for food are under attack from insects, fungi, bacteria, viruses, rodents and other animals, and must compete with weeds for nutrients. To kill unwanted populations living in or on their crops, farmers use pesticides. The first widespread insecticide use began at the end

of World War II and included DDT (dichlorodiphenyltrichloroethane) and gammaxene. Insects soon became resistant to DDT and as the chemical did not decompose readily, it persisted in the environment. Since it was soluble in fat rather than water, it biomagnified up the food chain and disrupted calcium metabolism in birds, causing eggshells to be thin and fragile. As a result, large birds of prey such as the brown pelican, ospreys, falcons and eagles became endangered. DDT has been now been banned in most western countries. Ironically many of them including USA, still produce DDT for export to other developing nations whose needs outweigh the problems caused by it. The most important pesticides are DDT, BHC, chlorinated hydrocarbons, organophosphates, aldrin, malathion, dieldrin, furodan, etc. The remnants of such pesticides used on pests may get adsorbed by the soil particles, which then contaminate root crops grown in that soil. The consumption of such crops causes the pesticides remnants to enter human biological systems, affecting them adversely. An infamous herbicide used as a defoliant in the Vietnam War called Agent Orange (dioxin), was eventually banned. Soldiers’ cancer cases, skin conditions and infertility have been linked to exposure to Agent Orange. Pesticides not only bring toxic effect on human and animals but also decrease the fertility of the soil. Some of the pesticides are quite stable and their bio- degradation may take weeks and even months. Pesticide problems such as resistance, resurgence, and heath effects have caused scientists to seek alternatives. Pheromones and hormones to attract or repel insects and using natural enemies or sterilization by radiation have been suggested.

Dumping of solid wastes

In general, solid waste includes garbage, domestic refuse and discarded solid materials such as those from commercial, industrial and agricultural operations. They contain increasing amounts of paper, cardboards, plastics, glass, old construction material, packaging material and toxic or otherwise hazardous substances. Since a significant amount of urban solid waste tends to be paper and food waste, the majority is recyclable or biodegradable in landfills. Similarly, most agricultural waste is recycled and mining waste is left on site. The portion of solid waste that is hazardous such as oils, battery metals, heavy metals from smelting industries and organic solvents are the ones we have to pay particular attention to. These can in the long run, get deposited to the soils of the surrounding area and pollute them by altering their chemical and biological properties. They also contaminate drinking water aquifer sources. More than 90% of hazardous waste is produced by chemical, petroleum and metal-related industries and small businesses such as dry cleaners and gas stations contribute as well.

Solid Waste disposal was brought to the forefront of public attention by the notorious Love Canal case in USA in 1978. Toxic chemicals leached from oozing storage drums into the soil underneath homes, causing an unusually large number of birth defects, cancers and respiratory, nervous and kidney diseases.

Deforestation

 

Soil Erosion occurs when the weathered soil particles are dislodged and carried away by wind or water. Deforestation, agricultural development, temperature extremes, precipitation including acid rain, and human activities contribute to this erosion. Humans speed up this process by construction, mining, cutting of timber, over cropping and overgrazing. It results in floods and cause soil erosion. Forests and grasslands are an excellent binding material that keeps the soil intact and healthy. They support many habitats and ecosystems, which provide innumerable feeding pathways or food chains to all species. Their loss would threaten food chains and the survival of many species. During the past few years quite a lot of vast green land has been converted into deserts. The precious rain forest habitats of South America, tropical Asia and Africa are coming under pressure of population growth and development (especially timber, construction and agriculture). Many scientists believe that a wealth of medicinal substances including a cure for cancer and aids, lie in these forests. Deforestation is slowly destroying the most productive flora and fauna areas in the world, which also form vast tracts of a very valuable sink for CO2.

Effects of Soil Pollution

Agricultural

  •  Reduced soil fertility
  • Reduced nitrogen fixation
  • Increased erodibility
  •  Larger loss of soil and nutrients
  • Deposition of silt in tanks and reservoirs
  • Reduced crop yield
  • Imbalance in soil fauna and flora

Industrial

• Dangerous chemicals entering underground water

• Ecological imbalance

• Release of pollutant gases

• Release of radioactive rays causing health problems

• Increased salinity

• Reduced vegetation

After affecting the soil pollution issues they decided to control soil pollution and they give more attention to the waste management plans and they spent a portion of their income to the municipal waste management .The Hindu newspaper report about neyyattinkara municipality is given below which shows how they manage their soil problems. Why do we adopt this types of  changes in our nation?

 Neyyattinkara municipality turns to natural farming

The Neyyattinkara municipality plans to launch a novel project to promote natural farming for the cultivation of organic vegetables.

The project, to be implemented in association with Agriculture Department and NIMS Medicity, is based on the Zero Budget Natural Farming (ZBNF) technology propagated by agriculturist Subhash Palekar.

ZBNF is an emerging trend in agriculture that propagates use of natural manure and nutrients for farming instead of chemical fertilizers and pesticides. Unlike organic farming, this method of farming focusses on using things that are naturally available inside or around the farm so that nothing is purchased from outside.

“Most prominently, it focusses on the use of dung and urine of local breeds of cows that are considered to be the best source of nutrients and microbes for cultivation. This method has been successfully tested in Palakkad district and has proven to give high yield in vegetable cultivation,” Neyyattinkara municipality secretary G. Sudhakaran said.

Municipality chairman S.S. Jayakumar said a detailed project report would be submitted to the government soon. “NIMS Medicity has consented to give six acres of land for implementing the project. The idea is to involve Kudumbasree workers for doing the cultivation at the farm. The municipality is also planning to open an outlet at the farm itself for marketing the vegetables. We expect to launch the project within two months,” he said.

Control Techniques

Numerous soil erosion control techniques, including the best management practices (BMPs), have been developed in many advanced countries. These techniques are basically based on the control of the major factors affecting soil erosion and have greatly contributed in cutting down soil erosion to meet the allowable soil erosion (or tolerable soil loss, T-value) criterion. Korea has not established the allowable soil erosion standard but the USA has set up the allowable soil erosion of 11 t/ha/yr in the 1960s (Mutchler et al. 1994). It is based on the assumption of an average 1 mm sheet erosion of a soil surface. However, the allowable soil erosion can be adjusted by a local government to meet the local water quality criteria. For example, Hudson (1981, quoted from Shin and Kim 2001 and reference not listed) proposed the allowable soil loss of 2 t/ha/yr for common agricultural fields and 1 t/ha/hr for water quality-sensitive area by NPS pollution.

A few guidelines for soil erosion control in Korea have been proposed. In the province of Jeju, land use is grouped into three categories: absolute conservation area, moderate conservation area, and sustainable development area (Table 3). The moderate conservation area is again subgrouped into three classes. It is based on the soil loss from 50 m-long sloped field (Yoon et al. 1997). Ha et al. (2004) proposed a general guideline based on the size of soil erosion and compared with OECD standards .These are only guidelines and have no legal binding authority. The allowable soil erosion standard that has legal binding authority is the most powerful and effective tool to enforce and persuade farmers to adopt the erosion control techniques.

Soil erosion control techniques are theoretically simple and easy but practically dirty, tough, time-consuming, laborious, controversial, and costly. Also, soil erosion techniques are very much site-specific. One technique can be successfully applied to reduce the soil erosion on a site but success cannot be guaranteed on another site if it is not modified to reflect site-specific characteristics. Soil erosion control strategies can be approached in three ways: administrative system approach, public relations and training, and technical approach.

Administrative System Approach

Administrative system approach is a key to the success of soil erosion control in Korea. The system should be well organized and supported by laws and the members of the system should well understand the soil erosion processes and the factors affecting soil erosion as well as hydrology and hydraulics. Also, the government should set up the allowable soil erosion criterion in terms of the amount of sediment discharge at the edge of a field. It is believed that the local administrative offices in Korea are well established and they provide excellent public services to the local citizens for general and routine affairs. But because the office personnel is mostly composed of non-engineers who do not understand engineering principles and practices related to soil erosion control, there may be many trials and errors in developing and implementing policies to reduce soil erosion and muddy runoff from the uplands. As a matter of fact, the policies have not been satisfactory.

Many measures must be carried out to successfully control soil erosion in Korea. One of the most urgent measures for the Korean government to carry out is the education of public domain workers who practically execute the government budget in planning and performing soil erosion control projects. Also, private consultants and construction engineers who are willing to design and perform soil erosion control projects must take soil erosion control training courses offered by workshops and institutions that have a specialty in soil erosion control. Because government budgets have been executed by the two groups who do not understand soil erosion control techniques, the soil erosion plans by local administrative offices could not be carried out satisfactorily.

Setting up of the allowable sediment at the edge of a field is also one of the most urgent tasks. Based on the allowable sediment, BMPs can be effectively chosen and practiced. If the set of BMPs to reduce soil erosion from a field cannot meet the allowable sediment discharge, the field can be forced to change the land use to produce less soil erosion. For example, land uses of vegetation cultures to row crop cultures and eventually to grassland or forest can be forced. In this case, farmers or landowners must be compensated for their losses by the land use changes by the government.

Soil erosion control projects must be continuously supported by a large government budget. In most cases, soil erosion control structures are not permanent ones and may be destroyed, buried, lost, or damaged by runoffs and floods caused by severe storm events. Those soft and hard soil erosion control structuresshould be continuously reinforced and repaired to maintain the designed purposes. Minor maintenance operations need to be done primarily by farmers and landowners. And if the maintenance works are beyond the landowner’s ability, local construction engineers may be hired by the local administration to fix the problem. Land purchase or lease for the soil erosion structures, regular and irregular maintenance works, and incentives to farmers for the loss of land productivity and the cooperation of maintenance works need money, not small but large budget every year. The Korean government announced a comprehensive plan to reduce soil erosion and muddy runoff from the alpine uplands by the end of October 2004. More than 2.2 million US dollars will be invested from 2006, for 10 years, according to the plan. The success of the plan is largely dependent on the conditions described above.

Public Relations and Training

Theories, principles, and techniques to cut down soil erosion and muddy runoff from sloping uplands have been well established in environmentally advanced countries. However, adoption of these techniques is dependent on the citizens’ support and the decision makers’ intentions. When the general public asks its government to reduce sediment and other NPS pollutants to protect and conserve water quality, a decision maker can easily adopt the techniques and allocate the necessary budget. Other important variables for the successful implementation of sediment and muddy runoff reduction policies are the farmers and landowners. Unless they are willing to accept the soil erosion control techniques on their lands and in their agricultural management practices, no policies and techniques can be successful. Farmers can voluntarily accept the techniques only when they understand the impacts of sediment and muddy runoff from their lands on a receiving water body, when they feel a strong responsibility for the degradation of water quality, and when they are sincerely motivated to stop soil erosion in their lands. Hefty incentives to farmers can greatly help them decide to adopt the necessary soil erosion control techniques.

By providing various free incentives, low interest loans, and other benefits without any conditions, the Korean government has been helping farmers. However, it is strongly recommended that the government must ask farmers to take certain soil erosion control classes before they apply for government incentives. It is an easy way to educate and train farmers. Korea has a well-established agricultural extension service system. Extension service personnel generally have agricultural backgrounds but are not familiar with soil erosion control techniques. It is also strongly recommended that the extension service personnel be trained about the soil erosion control techniques so that they can discuss and educate farmers at the site. It should be kept in mind that the voluntary participation of farmers in the soil erosion reduction campaign is the best way, technically and economically, to achieve the goal of long-term soil erosion control.

Technical Approach

Soil erosion control techniques are very much site-specific. It means that a technique may be successful on a site but may not work on other sites. Although numerous soil erosion techniques have been developed in many advanced countries, these techniques may not be directly applicable to agricultural fields in Korea because of the differences in soil, slope, crop, customary agricultural management, rainfall, and so on. However, because the basic theories, principles, and practices of soil erosion control techniques are the same, some of these can be applied in Korea with minor modifications and after verification experiments. Verification experiments are complex, laborious, and costly in most cases. Only a few researchers and institutions have been conducting these experiments in Korea.

BMPs for soil erosion control for plain and mild-sloped fields are not much different from those of other countries. However, BMPs for steep-sloped uplands in Korea may be quite different from those of other countries. The emphasis of this paper is placed on the soil erosion control techniques for the steep-sloped uplands in the alpine belts of 400 m above the mean sea level in the Korean Peninsula.

It is known that the dominant factors affecting soil erosion are land slope and length, amount of land cover, inherent erodibility of the soil, and rainfall characteristics. The alpine uplands in Korea unfortunately have more than sufficient conditions to meet the worst combination of the dominant factors. The slope and the length of the uplands are generally very steep and long, the sandy soil is very much erodible, the surface is never covered by residues, and rainfall is very intensive. It is no wonder that the uplands dump a huge amount of sediment and muddy runoff into receiving waters. As described earlier, a 5 m x 30 m runoff plot with 28% slope and 54 mm rainfall in 40 minutes produced about 72 t/ha of sediment. Controlling soil erosion is not a matter of improving soil quality by increasing organic matter content. It is a matter of controlling runoff. So, erosion control strategies must be directed to reduce or bypass surface runoff by all means.

The following BMPs are mainly focused on the reduction or the bypass of runoff and the removal of sediment during conveyance to a receiving water. Sediment basin and trap, terrace, drainage channel, check dam, weir (e.g., concrete drop structure and chute, gabion), and wetland are considered as hard BMPs. Surface cover, vegetative filter strip, tillage method and mark (e.g., no till, reduced till, contour till) are considered as soft BMPs. The hard and soft BMPs must be functionally combined to get the best results. These BMPs for soil erosion control can be schematically developed as shown in Fig. 1.

Soft BMPs. Surface cover and tillage method and mark are the two main BMPs to reduce runoff and erosion at the source. It is proven that the tillage mark of contour does not significantly reduce soil erosion. Contour tillage mark can work well to reduce runoff and erosion if rainfall is small. However, if rainfall is large enough to fill the furrow, the ridge is destroyed, the water in the furrow suddenly flushes downslope, consequently destroying the ridges downstream to form large rills and gullies, resulting in a huge sediment discharge. Therefore, contour tillage mark practices are not very effective when a large rainfall is expected.

Reduced till and no-till practices can be good alternatives to reduce erosion from the steep-sloped uplands if grain crops such as corn, soybean, wheat, and barley were cultivated. But the major crops in the high mountain alpine fields are potato, Chinese cabbage, radish, carrot, and other vegetables. These crop cultures need conventional tillage and the surface is completely disturbed before transplanting or seeding is made every year, making the soil soft and easily erodible.

The last alternative left to reduce runoff and erosion at the source is surface cover. As shown in Table 1, the 100% covered sandy soil plots did not produce runoff while the bare plots released runoff of 71.8% of the provided rainfall. Soil retention and groundwater runoff also showed a large difference between the covered and the bare soil plots. The problem is that surface cover with the vegetable cultures is not easy and may not be economical. It is well proven that the source control of NPS pollution is the best both technically and economically. If so much soil is eroded every monsoon season and the water quality of the receiving water is sensitive, it is well worth applying the surface cover method. Loose rice straw mats can be used to cover the surface.

A vegetative filter strip (VFS) is an alternative to retain sediment in runoff. VFS can work well in the uplands where the slope is mild, and runoff does not form large rills. However, where the land size is small and concentrated runoff occurs like in the alpine uplands, VFS may not work well to remove sediment in the runoff. Munoz-Carpena and Parsons (2005) developed the VFSMOD-W that could estimate filter length, width, slope, and vegetation to meet a sediment reduction. But they recommended that the model be applied to smooth slopes, typically less than 10%. In the USA, VFS is required to remove 75% of sediment to meet the total maximum daily load (TMDL) criterion. Considering that a 5 m x 30 m runoff plot on 28% sandy loam soil produced sediment up to 72 t/ha/event, it could easily be imagined that no VFS could stand the sediment load. Before a VFS is made on a field, it is strongly recommended that it undergo the experiments on the width and VFS vegetation if it would be installed at the edge of steep-sloped uplands.

There are many other soft alternatives to reduce soil erosion from the uplands. One of them is the coir net that is woven with palm tree fiber. It takes 3-4 years for the net to decay in the wild environment. Various types and forms of coir net products are placed at the edge of a field and mulched on a slope to minimize soil erosion.

Adding huge amounts of soil has become customary in some uplands where crop rotation is not practiced and soil sickness is experienced. The depth of fresh soil layer added is sometimes deeper than 20 cm. Weathered granite soil (sandy or sandy loam soil) that contains practically no nutrients is usually quarried from a mountain and placed on the existing field. If soil is continually added, the elevation of a field becomes higher than the adjacent roads. In this case, rainfall runoff may be drained through the roads and the roadside soil may be severely eroded. To prevent these from eroding, a 20-30 cm-high concrete sill may be made along the roadside.

Hard BMPs. Terrace, sediment basin and trap, drainage ditch and channel, diversion and catch drain, grassed waterway, tile drain, grade stabilization (drop or chute) structure, and constructed wetland are some of the examples of hard BMPs that can be applied on steep-sloped uplands in Korea. The basic concept of these BMPs is the safe drain of surface runoff so that it does not form rills and gullies. If no rills and no gullies were formed, soil erosion would decrease drastically. Therefore, the BMPs need to be functionally combined to minimize the formation of rills and gullies and to drain the runoff to a channel where it can be discharged into the drainage system. This job may involve so much work and so many farmers and local engineers who do not have soil erosion control experiences and may not understand the nature of erosion control works. They may even think of giving up land cultivation altogether. These BMPs are not easy to do but they have to be done to stop erosion. Otherwise, the land uses may have to be changed to less erodible uses such as grassland or forest.

Terrace is a good alternative to remove sediment in runoff and safely drain surface runoff through drain pipes. A terrace in small-sized lands is similar to a small sediment basin that is mainly made of a small dry pool. A dry pool can be placed at the end or in the middle of a field where concentrated runoff passes or discharges. The dry pool receives runoff from the upper field and the runoff is drained directly or through drain pipe(s) to a drainage channel or nearby stream. While the runoff passes the pool, velocity is drastically reduced, and much of the sediment in the runoff, except the clayey particles, is deposited. The sediment removal rate of the small pool is amazingly high in sandy soil fields.

Catch drain, diversion, drainage channel, and sediment basin or trap can play key roles as a system in controlling sediment discharges. The slope of these waterways must be mild enough to decrease runoff velocity and to deposit the sediments in runoff in the waterway. If a slope is too steep and the water velocity is too high to deposit sediments, drop, chute or grade stabilization structures must be constructed to make the slope smooth. Where a concentrated flow flows into the waterway, a section of the waterway must be enlarged to accommodate the depositing sediments. It is because the runoff velocity decreases where it meets the waterway and the runoff sediments may suddenly block the waterway. Sediments do not evenly deposit over the wide area but they immediately settle down where the runoff losses its transport capacity as the velocity decreases. The enlarged section may be called a sediment trap or basin. It is believed that the waterway system of catch drain, diversion, drainage channel, and sediment basin can functionally work well and remove much of the runoff sediment. The author’s experiment proved the sediment removal of more than 95% with a small sediment basin. One of the disadvantages of this approach was the need to remove and empty the basin and waterway after every severe rainfall event that produced a large sediment volume.

A drainage channel system in the upland area is not well established in Korea. The construction of catch drain, diversion, drainage channel, and sediment basin systems may require a large land size, farmer’s agreement, and considerable budget. However, it also is understood that without the system, the reduction of sediment and muddy runoff from sloping uplands may not satisfy the water quality standards.

Sediment basin itself can remove sediment effectively if it is properly constructed and maintained. Because of intensive land uses in Korea, it is not desirable and economical to build a large sediment basin. But it is recommended that a sediment basin be built at the mouth of a field where runoff is concentrated and discharged. The size of the sediment basin may be designed to hold the sediment volume that can be discharged by two to three large rainfall events. After each sediment discharge event, the basin must be emptied for the next storm event. The design and construction manual of a sediment basin for upland cultures has not been established in Korea. However, references on simple and easy methods of designing a sediment basin are available (Ohio Department of Natural Resources 1996).

A favored design is the tile drain where interflow seeps to the surface during the monsoon season. Grassed waterway may be a good alternative to remove sediment in runoff while safely draining runoff. But because it takes a relatively large area and needs careful maintenance, it may not be accepted by farmers. Paddy as a constructed wetland may be an alternative if it is functionally combined with a drainage system that is composed of catch drain, diversion, drain channel, and sediment basin. An upland watershed is divided into small sub-watersheds. And at the mouth of each sub-watershed, a paddy or a cascade of paddies is prepared to accept the runoff from the drainage system. The paddy then further settles down the fine particles in runoff from the drainage system.

 

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One response to this post.

  1. Posted by HORNBILL on December 18, 2011 at 7:58 am

    you people did a good job.You took a good study about your environment.Its is an informative one.You said about some control techniques that were done by Korean govt: ,is it possible here?

    Reply

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