Shin Jinma

ordinary flood discharge

A permanent flood discharge is a gate facility that allows water from a dam lake to flow downstream while regulating the flow. It is used for normal flood control, while an emergency flood discharge is used for floods that are too large to be discharged by the normal flood discharge. A permanent flood discharge is generally equipped with a gate, but there are also some that have no gate but a hole.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

normal level of water supply

The normal full water level is the highest water level that can be stored in the dam lake for water utilization purposes (water supply, irrigation, industrial water, etc.) during normal times (non-flooding). The water level can be used from this level to the lowest level. Each dam has its own set of operating rules, and the full water level is determined based on the elevation of each dam, and the rules for operating gates, etc. are based on this level.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

gravity-fed concrete dam

A gravity-type concrete dam is a dam made of concrete that can support water pressure by its own weight. It requires a large amount of concrete to construct, and the foundation bedrock must be very solid. It is the most robust of the several types of dams and has high durability against earthquakes and floods.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

gravity arch dam

A gravity arch dam is a dam that has the advantages of both gravity and arch concrete dams. The advantages are that it does not require a strong bedrock as in the case of an arch dam, and it does not require a large amount of concrete as in the case of a gravity concrete dam.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

dead-water capacity

The dead water capacity is the capacity between the top of the sediment capacity and the lowest water level, and is set to maintain a certain water level. Since dead water itself is not a target for water utilization and the water level itself is below the intake, it is used for emergency pumping in case of abnormal drought.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

experimental flood

Test flooding is a test to check whether there are any problems with the dam after its completion. The test waterflooding is to check if the dam can withstand the water pressure and if there is any leakage from the embankment, and is, in a sense, the "Tennozan" of dam construction.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

minimum water level

The minimum water level is the water level at the top of the sediment, assuming that the sediment capacity of the dam is horizontal. Water above this level can be used for irrigation and other purposes. Conversely, water below this level cannot be used, which means that in most cases there is no water intake below this level.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

surcharge water level

Surcharge means "overload" or "overload" and refers to the level at which water can be temporarily stored in a dam lake up to its limit during a flood event. It is the level of water that can be temporarily stored up to the limit of the dam lake in the event of a flood, which generally occurs once every 100 years. During test flooding, water is stored up to this level, and the test is conducted by gradually lowering the water level.

"sa" column or row of the kana syllabaryIntroduction to Damsdam terminology

conduit gate

A pipe installed for flood control or downstream discharge. Holes at the bottom of a dam are sometimes collectively called conduits. The original meaning of the word "conduit" is "conduit," and it is so called because it is installed through the embankment. A conduit is also equipped with a gate, which is called a conduit gate. Conduit gates are used as permanent flood discharges during relatively normal discharge.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

aggregate

Aggregate is the raw material used to make concrete to construct dams. Sand, crushed sand, gravel, and crushed stone are mainly used as aggregate. Aggregates are classified as fine aggregate if they pass through all 10mm sieves and 85% or more by weight through 5mm sieves, and coarse aggregate if they remain 85% or more by weight on 5mm sieves.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

flood capacity

Flood capacity refers to the capacity from the constantly full water level or flood stage limit to the surcharge water level.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

Flood discharge

A flood discharge is a gate facility used to channel water from a dam lake downstream. The inflow section, the conduit section, and the force reducing works are collectively called a flood discharge. There are two types of flood discharge: permanent flood discharge and emergency flood discharge. The so-called "dam bore," which was popular on the Internet for a while, is also called "morning glory-type flood discharge" or "morning glory-type flood discharge" because a shaft is installed in the dam lake and its mouth looks like a morning glory, but its official name is "tateko-gata-kozu-baki" (vertical shaft-type flood discharge).

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

Flood control capacity

Flood control capacity is the capacity from the constantly full water level to the surcharge water level. Flood control is carried out within this capacity. In particular, during flood periods, the water level is lowered to the flood stage limit to ensure the volume of water flowing into the dam. A dam with no flood control capacity has no flood control function.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

Flood stage limit water level

Flood level limit refers to the water level established at dams for flood control purposes, and refers to the water level that is lowered below the full water level at all times during flood periods to prevent flooding.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

flood season

It refers to periods of high precipitation, such as the rainy season and typhoon season (mainly from June to October). Therefore, just before the flood season, the water level of the dam lake is lowered to prepare for flooding. Some dams have a specific time of year for flood control. For example, the Muromaki Dam in Toyama Prefecture is open from June 21 to September 30, dams directly under the Abukuma River system are open from June 11 to October 10, the Ren Dam in Mie Prefecture is open from June 16 to October 31, and the Okura Dam in Miyagi Prefecture is open from July 1 to September 30.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

flood

Flooding indicates a significant increase in the level or volume of water in a river. Factors that increase the volume of water include heavy rainfall and snowmelt. Also, a flood occurs when the flow from upstream to the dam lake is higher than usual, even if the river is not overflowing. In the case of weather forecasts, a flood is called a flood when the water level gauge of a river exceeds the warning level, which is the basis for issuing a flood warning.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

rough-coated rock

A rough stone pile is a pile from which materials necessary to construct a dam are extracted. Aggregate, the raw material for concrete, and fill material for rock-fill dams are mainly collected. The materials are collected from a mountain near the embankment, but some dams may be set up at unexpectedly distant locations. The materials are transported by cable cranes and 46-ton or other super-large dump trucks.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

0505-Otori Dam

Located downstream from Okutadami Dam, this is a dedicated power generation dam owned by J-Power Development. It is off-limits to the general public. We arrived at the Otori Dam on the back of a microbus provided by Power Supply Development Co. Again, I had not studied the dam beforehand, so I did not know the details of the dam. Although we could not see the entire embankment due to the power plant building, the solid appearance of the embankment is unique to the gravity-type arch. The white object hanging down from the right bank of the embankment is a hydraulic pipe for power generation. / Gravity arch dam / 83m

Fukushima Prefecture Dam

momentum reducer

A momentum reducer is a structure that prevents water from flowing out of a flood discharge because the energy of the water flowing out of the discharge can be quite large, which may cause the point where the water falls to be cut off. It is literally a structure that reduces the momentum of the water. There are several types of momentum reducing structures, and they are selected according to the dam type, geology, and surrounding environment.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

Planned high water flow rate

Planned high water flow rate indicates the river flow rate when flood control is carried out by a dam after the dam is constructed, compared to the base high water flow rate. In other words, the planned high water flow rate is the flow rate obtained by subtracting the amount of flood control by flood control facilities such as dams from the base high water flow rate. The water level at which the planned high water flow rate is displayed as a river channel cross section is called the planned high water level.

"ka" column or row of the kana syllabaryIntroduction to Damsdam terminology

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