Banqiao dam

Banqiao dam failure inHenan, China The Banqiao Reservoir Dam in Henan province failed in caused more casualties than any other dam failure in history at an estimateddeaths and 11 million displaced. The dam was later rebuilt. Description In response to severe flooding and to ensure electrical power generation, China built the Banqiao Dam in the Huai river basin of the Henan province. It was completed in

Banqiao dam

Flood gates are an expensive component of a dam's construction so engineers must consider a trade-off between the cost of the dam and Banqiao dam security it will provide.

The dam design determines the probability that a storm will cause the dam to overflow and possibly destroy the structure. If this probability is 0. This terminology is misleading because it implies that severe storm occurrences are independent random events whereas this is not the case.

The random events may be the weather conditions. The Banqiao dam conditions that produces one severe storm may persist and produce another severe storm not long afterwards. Hurricanes and other tropical cyclones tend to be spawned in sets so one severe hurricane may be followed by others in a short period of time.

The policy of operation for the dam is a factor in determining the probability of catastrophic failure. If a dam is held empty it has the greatest capacity for control of severe floods.

But such a policy would destroy the usefulness of the dam for storing water for providing irrigation water. And if the dam reservoir is being kept empty then the small flood are not being controlled. On the other hand if the dam does not retain some unutilized capacity it will be useless for controlling flood dangers.

The dam authorities must decide the proper excess capacity to maintain based on the trade-off they see between the value of stored water versus the value of flood control. Note that in the matter of using dams for flood control it is a question of reducing the cost of small floods at the expense of increasing the damage from the floods which bring about the catastrophic failure of the dam because the water stored behind the dam will be added virtually instantly to the flood.

The failure of one dam will quite likely lead to the failure of other dams down stream. The effect will be cumulative. Some simple algebra shows the nature of the problem.

Banqiao dam failure in 1975, Henan, China

Let the storage capacity of a dam be C and let G be the rate at which water can be passed through the dam based upon the number and size of the flood gates built into the dam. Let the unutilized capacity of the dam be E and the normal stored water be A. A storm may be characterized by the magnitude of the flow at the dam site F and the duration of the flow D.

The rate at which the dam fills up is given F-G. The dam authorities have to consider the effect of design and operating policy choices on an objective function of the form where f A is the value of having stored water of amount A, is the probability of a dam failure and is the downstream cost of the failure.

Banqiao dam

The probability of a dam failure is a matter of the probability of the combination of F and D and. China has been plagued with severe floods from time immemorial.

The area where the weather systems from the north from North Central Asia meet the weather systems from the south from the South China Sea is particularly hard hit.

This is the region of the Huai River. Inshortly after an episode of severe flooding in Huai River Basin, the government of the People's Republic of China announced a long term program to control Huai River system.

It was called, "Harness the Huai River. There were numerous smaller dams built as well. The Bangiao Dam was originally designed to pass about cubic meters of water per second through sluice gates and a spillway.

The capacity storage capacity was set at million cubic meters with million cubic meters of this capacity reserved for flood storage.

Understanding the Banqiao Dam Failure

The height of the dam was at little over meters. There were some flaws in the design and construction of Banqiao Dam, including cracks in the dam and sluice gates. With advice provided by Soviet engineers the Banqiao Dam and the Shimantan Dam were reinforced and expanded.The nearby Banqiao dam, which crossed the powerful Ru River, was designed to handle a half meter of rainfall over three days.

It had rained six times that much. Because of flooding further down the valley, workers had been ordered not to release too much water from the Banqiao dam. Wednesday, 13 August of 1 2.

BANQIAO RESERVOIR DAM FAILURE ENGINEERING DISASTER CASE STUDY CASE STUDY Over dams were built . The Banqiao Dam had been built on the Ru River in the early s as part of a flood-prevention and electricity-production program aimed at controlling the Huang He (Yellow River).

At a height of feet ( metres) and with a storage capacity of some Construction of the Banqiao dam began in April on the Ru River with the help of Soviet consultants as part of a project to control flooding and provide electrical power construction was a response to severe flooding in the Huai River Basin in and .

In , after a period of rapid dam development, a perfect storm of factors came together to topple Henan Province's Banqiao Dam and kill an estimated , people. Today, on the cusp of another dam-building binge, some worry that factors which led to Banqiao's collapse are re-emerging.

The pass-through of the Banqiao Dam was to protect against a year flood, which was estimated to be one from a storm that would drop meters of rain over a three day period.

The Shimantan Dam was to protect against a year flood, one from a storm that drops meters of rain over a .

Banqiao dam failure in , Henan, China | EJAtlas