The Common Problems Associated With Dams Environmental Sciences Essay
A Dam is a physical barrier constructed across a river or a waterway to command the flow of or raise the degree of H2O. The intent of such a building may be flood control, irrigation demands and coevals of hydroelectricity. A dike is a barrier across fluxing H2O that obstructs, directs or slows down the flow, frequently making a reservoir, lake or impoundings.
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Most dikes have a subdivision called a wasteweir or weir over which, or through which, H2O flows, either intermittently or continuously, and many have hydroelectric power coevals systems installed. The dikes are advantageous in more than a individual manner. Advantages of a dike are listed below:
They are helpful in forestalling inundations.
They serve as a solution to energy crises by bring forthing hydroelectricity.
They prove to be helpful in irrigation
They better the H2O conveyance.
And last but non the least they attract tourers.
Dams are excessively good for world but at the same clip they are harmful excessively in several ways. Disadvantages of a dike are listed below:
Constructing a dike is an expensive matter.
For constructing a dike a immense population of nearby country is moved.
The life environment of aquatic and semi aquatic vegetations and fauna gets disturbed in lower instance.
Collapse of the dike causes great harm.
Fig 1 Dam [ www.timboucher.com ]
Now in this paper we will be sing and detecting the chief causes of Dam Failure along with instance survey for every cause. Main causes of Dam Failure are:
Spillway planing mistake.
Skiding of mountain into the dam lake.
Poor care particularly of outlet pipes.
We will be discoursing all of the above mentioned causes one by one. Besides all the above causes there is one more ground due to which dikes are collapsed. In proficient footings it is called Deliberate Dam Failure. This happens during the class of War. When force of one state destroys the dike of other state intentionally so this is known as Deliberate Dam Failure. As this cause is nat a common cause so we would non see this in our survey.
SPILLWAY DESIGN ERROR
Spillway ( shown in Fig 2 ) is a characteristic construction of a dike which is used to supply controlled release of flows of H2O from the dike into the downstream. Spillways release inundations so that the H2O does non dominate and damage or even destruct the dike. There are two ways of wasteweirs: Controlled and Uncontrolled.
Controlled Spillway: It has Gatess which regulate the H2O. This design gives us an chance to work the full tallness of the dike and inundation Waterss can be released as required by opening one or more Gatess.
Uncontrolled Spillway: It does non hold Gatess, when the H2O rises above the lip of the wasteweir it begins to be released from the reservoir. The rate of discharge of H2O is controlled merely by the deepness of H2O within the reservoir. All of the storage volume in the reservoir above the wasteweir lip can be used merely for the impermanent storage of floodwater, and can non be used as H2O supply storage because it is usually empty.
Fig 2 Spillway [ www.wikipedia.com ]
CASE STUDY: The South Fork Dam
As a instance survey under this cause of Dam Failure we will analyze the destruction of South Fork Dam which was located on Lake Conemaugh, an unreal H2O organic structure located near South Park, Pennsylvania, USA. On May 31, 1889, the South Fork Dam failed and 20 million dozenss of H2O from Lake Conemaugh explosion through and raced 14 stat mis ( 23 kilometer ) downstream, doing the Johnstown Flood.
History of South Fork Dam
The South Fork Dam was built by the Commonwealth of Pennsylvania between 1838 and 1852 as a reservoir for the canal basin in Johnstown. The dike is located 14 stat mis upriver from Johnstown. The Comenaugh River runs through the bosom of Johnstown and it had been made narrower in order to construct more constructions on it Bankss. The river was susceptible to deluging due to it & amp ; acirc ; ˆ™s location on a inundation field. The Commonwealth of Pennsylvania sold the dike to the Pennsylvania Railroad in 1857. With the reaching of rail service in 1852, the usage of the canal for bringing of goods took a downswing. The South Fork Dam was abandoned and allowed to travel into a province of disrepair. In 1862, portion of the culvert gave manner but was ne’er repaired. In 1879, a group of business communities formed a company and called it the South Fork Hunting and Fishing Club. They purchased the dike with the purpose of constructing a summer resort on Lake Comenaugh for affluent Pittsburg households. Plans included take downing the dike in order to construct a route on top and raising the degree of the lake. The nine continued to do changes to the dike and in the terminal, the lake was 450 pess higher than Johnstown. [ suit101.com ]
From the above abstract we can easy do out that the sick care of the wasteweir and rise of the degree of river made the status worse and eventually the uninterrupted rain made the Dam collapsed. After the Dam gave up about approximately 20 million dozenss of H2O spilled over the dike and Jhonstown was hit without any anterior warning. The H2O headed towards the town with a velocity of about 40 stat mis per hr. The inundation played mayhem and made over 2,200 people lose their lives and all over harm was estimated to be $ 17 million. This was the first major catastrophe faced by the newly-formed American Red Cross. Aid came from 18 states across the Earth. The South Fork Dam Break is shown Below [ Fig 3 ]
Beside the Spillway failure there are other causes which are responsible for the Disaster and they are:
Heavy and uninterrupted Rainfall.
Rising H2O caused eroding of new embankment which was made up of clay and straw.
Fig 3 South Fork Dam Break [ www.accuweather.com ]
Precautions which could hold saved South Fork Dam:
The chief cause of the interruption was Spillway design mistake. There were deficient wasteweirs which made the tremendous sum of H2O to slop. If there had been more spillways so the catastrophe would hold been avoided.
The damaged parts of the dike should hold been repaired.
The new parts should hold been made up of concrete alternatively of rock, clay and straw.
SLIDING OF MOUNTAIN INTO THE DAM LAKE
A dike is made at the base of a river and in between a vale which means that the lake or H2O organic structure which is dammed has mountains on both side of it. Now as a dike is made the natural geological balance is disturbed and these mountains get loosen up and develops clefts which causes landslides to happen. These landslides pose a great menace when they fall in the lake. If a landslide of great volume falls in the lake so it raises the H2O degree to a great extent and that excessively all of a sudden. This sudden rise makes a immense sum of H2O to slop over the dike doing tsunami ( seiche moving ridge ) . This moving ridge brings a monolithic inundation and devastation to the vale below which wipes a great country.
CASE STUDY: The Vajont Dam
As a instance survey under this cause of Dam Failure we will analyze the destruction of Vajont Dam [ shown in Fig 4 ] which was located on Vajont River under Monte Toc, 100 kilometers north to the Venice, Italy. It was responsible for the deceases of about 2,000 people in a 1963 landslide. One of the highest dike in the universe, it was 262 metres ( 860 foot ) high, 27 metres ( 89 foot ) midst at the base and 3.4 metres ( 11 foot ) at the top. The dike was built by SADE ( Society of Adriatic Energy Corporation ) , the electricity supply and distribution monopolizer in North-Eastern Italy.
History of Vajont Dam:
The building work of the dike started in 1950. In 1959 some slides were noticed and new surveies were made and the experts told SADE that the side of Mount Toc is unstable and is likely to fall in if the filling is continued. The survey and experts were ignored wholly. In October 1959 the building was complete and in February 1960 SADE was authorized to get down make fulling the basin. Equally shortly as the filling started and reached to certain degree boulder clay summers of 1960 minor land slides started taking topographic point. But even these slides were ignored and the few journalists who raised their voice were sued. Finally on 4 of November 1960 a landslide of about 800,000 three-dimensional metres collapsed in the lake. This made SADE to hold make fulling but it was started once more after take downing the degree by 50 metres and get down constructing an unreal gallery. The minor slides kept on taking topographic point and functionaries of SADE kept on foretelling the catastrophe but they were ignored.
On 9 October 1963 at about 10:35pm, the combination of ‘drawing-down the reservoir ‘ and heavy rains triggered a landslide of about 260 million three-dimensional metres of forest, Earth, and stone, which fell into the reservoir at up to 110 & A ; Acirc ; km per hr ( 68 & A ; Acirc ; miles per hour ) . The ensuing supplanting of H2O caused 50 million three-dimensional metres of H2O to over-top the dike in a 250-metre high moving ridge. [ 6 ] Despite this, the dike ‘s construction was mostly undamaged. Approximately 1900 to 2500 people were dead and 350 households were wholly wiped off.
The major causes of this catastrophe are:
The heavy 50 million three-dimensional metre landslide into the lake which made the tsunami moving ridge rose.
The other minor land slides in the lake and in the unreal gallery.
Heavy rainfall which paved the way for the catastrophe.
Major causes for the land slides are:
Perturbation in the geological balance of Mount Toc.
Continuous filling of the basin.
Time to clip rainfall.
Fig 4 Vajont Dam [ wikipedia.com ]
Precautions which could hold saved South Fork Dam: If anyhow the land slide could be prevented so the catastrophe might hold been avoided. The landslide can be prevented by following two methods:
Plantation: More and more workss on the offshore side of the mountain. The roots of the workss help in adhering the stones and dirt together and prevent eroding therefore land skiding. Terrace plantation is a good option.
By unreal mountain binding: In this procedure the mountain is bound with the aid steel cyberspace which prevent slides and even if land slide, the net prevent it from falling.
POOR MAINTENANCE ESPECIALLY OF OUTLET PIPES
Mercantile establishments came in scope of designs, sizes, stuffs and type of control. Most of the commanding mechanisms and conduits are normally submerged and are reasonably boring to entree for care every bit good as review. This is the ground of carelessness and some serious jobs start developing. The job can run from the control works going inoperable to the conduit deteriorating to the point of embankment failure. Proper review of the mercantile establishment normally requires advanced planning to let escapes to be shut off and afloat countries to be pumped out.
CASE STUDY: Lawn Lake Dam
Now as a instance survey under this subdivision we will do a thorough survey of Lawn Lake Dam [ Fig 5 ] . This dam failure occurred due to the disrepair of the mercantile establishment pipe which was located at the distant and boring location. The uninterrupted carelessness of remotely situated leaky pipes caused the catastrophe when on July 15, 1982 at 6 ante meridiem 830,000 M3 of H2O exploded out of the faulty pipes. This tremendous sum of H2O caused a brassy inundation and priced $ 31 million.
History of Lawn Lake Dam:
Originally the Lawn Lake was a natural lake covering a surface country of over 66,000 M3s. It was situated at a tallness of 3,400 m in the bouldery mountain. In 1903 some husbandmans seeking irrigation installations out of this lake, built a dike and the covering land of the lake increased to 190,000m3. It was started in 1902 and the dike was completed in 1903. The dike increased the storage capacity of this natural H2O organic structure. This dike was built in the eastern portion. The H2O from this dike was released through the steep channel into the Big Thompson River. As the dike was built in the bouldery mountain, its design was such that it made the location of mercantile establishment pipe quit remote. Bearing the carelessness of functionaries the dike survived 80 long old ages.
On the forenoon of 15 July 1982 the dike collapsed let go ofing 228 million gallons of H2O all of a sudden. This immense sum of H2O poured through the steep and narrow versant. It is said that there was enormous sound and the Earth shook. The release rate of H2O was 510 m3/s. Though this great aquatic violent disorder killed merely one individual bivouacing aboard but economically the cost of this catastrophe was estimated to be $ 31 million. The H2O got poured in the river and hit the cascade dike ensuing in ruin of the same adding more sum of H2O to the inundation. This inundation destroyed the Aspenglen campsite. Then after the inundation H2O entered the town of Estes Park and caused great harm to the business district stores after which the inundation joined Thompson River. This inundation deposited an alluvial fan of dust in Horseshoe Park.
Fig 5 Alluvial Fan [ wikipedia.com ]
Precautions that could hold saved the Lake Lawn Dam: Merely two safeguards would hold saved the black terminal of Lake Lawn Dam and they are
If the dike would hold been design in such a manner that the mercantile establishment pipes could hold been easy accessed so the fix work won & A ; acirc ; ˆ™t have been delayed and the escape could hold been avoided.
Seasonably mending work of the dike would hold saved this great harm.