TCVN 10406:2015: What are the regulations on documents of drainage for irrigation works in Vietnam? What is the land use structure in the drainage area?
- TCVN 10406:2015: What are the regulations on documents of drainage for irrigation works in Vietnam?
- What is the land use structure in the drainage area in Vietnam regulated in TCVN 10406:2015?
- TCVN 10406:2015: What are the general requirements for calculating design drainage coefficient for irrigation works in Vietnam?
TCVN 10406:2015: What are the regulations on documents of drainage for irrigation works in Vietnam?
TCVN 10406:2015 regulates documents of drainage for irrigation works as follows:
- The rain used in calculating the design drainage coefficient is the rain that causes waterlogging that can appear in the drainage area corresponding to the design frequency. Depending on the occurrence characteristics of the rains that cause waterlogging and the drainage requirements in the area, the rain used to calculate the design drainage coefficient can be a rain that causes waterlogging in one day (X1 d), or two days (X2 d). ), three days (X3 d ), five days (X5 d) or seven days (X7 d).
- Carefully analyze the statistical data of flood-causing rains that have occurred in the drainage area through the following basic characteristics of the rain to select the appropriate design drainage rainfall model and drainage time. If you encounter a situation where there are several types of flood-causing rain patterns with approximately the same number of occurrences (in terms of number of rainy days and rainfall pattern), choose the more unfavorable type:
+ The nature of the rains that cause waterlogging (the number of rains that cause waterlogging in one day is included in the rain that causes waterlogging in three days, the number of rains that cause waterlogging in three days is in the rain that causes waterlogging in five days, the number of rains that cause waterlogging in five days located in the rain that caused seven days of waterlogging out of the total number of rains that caused waterlogging that have been recorded). If this characteristic is common (occurring more than 50%), long-term rains that cause waterlogging will be more dangerous than short-term rains.
+ Common number of rainy days for waterlogging rains (see 3.10) and common distribution pattern of waterlogging rain patterns (with the highest number of occurrences).
+ The water drainage period (a month or several consecutive months during the rainy season) has the highest number of rains that cause waterlogging in the year. The period when the number of rains that cause waterlogging occurs accounting for 90% or more of the rains that cause waterlogging of the year is drainage period 1.
+ Time to stop raining after rains that cause waterlogging (also known as the time to stop raining between two consecutive rains that cause waterlogging).
- The rain model designed to calculate the drainage coefficient for a drainage area with many different drainage objects or to calculate the drainage coefficient for each type of drainage object present in the drainage area is a model of daily rain causing waterlogging (with The number of rainy days is 3d, 5d or 7d corresponding to the design frequency.
- For urban areas from special type to type III and concentrated industrial zones, or in cases where it is necessary to calculate drainage coefficient to design separate drainage works for this area, use the hourly rainfall model. of two days of flooding rain (48 h) corresponding to the design frequency.
- Calculating the design drainage coefficient according to the socio-economic development scenario for the entire region with a forecast period of 10 years or more, the design drainage model must consider the impact of global climate change. . Based on climate change and sea level rise scenarios for Vietnam, design consultants propose the level of impact of climate change that will change the total amount of drainage rainfall and change the distribution pattern of drainage rainfall design accordingly.
TCVN 10406:2015: What are the regulations on documents of drainage for irrigation works in Vietnam? (Image from the Internet)
What is the land use structure in the drainage area in Vietnam regulated in TCVN 10406:2015?
In TCVN 10406:2015, regulations on land use structure in drainage areas are specified as follows:
- It is necessary to collect data on land use structure in the drainage area, including maps of current land use status and land use planning maps, area and area ratio of each type of land according to current use status. land and according to land use planning to meet socio-economic development requirements.
- Documents on soil types in the drainage area must be analyzed and grouped into each type of drainage object according to 3.13.
- If the drainage area does not have a land use plan suitable for the future drainage coefficient calculation timeline, it must be based on the local socio-economic development plan and the level of change in use structure. land use in recent years as well as the specific conditions of the drainage area to forecast or build scenarios on the area ratio of different types of drainage objects accordingly.
TCVN 10406:2015: What are the general requirements for calculating design drainage coefficient for irrigation works in Vietnam?
In TCVN 10406:2015, the requirements for calculating design drainage coefficient for irrigation works are as follows:
- The design drainage coefficient must meet the allowable flooding requirements of water drainage objects present in the drainage area.
- When calculating the drainage coefficient, you must divide the water drainage time T into many small periods DT to calculate the drainage coefficient for each period. Depending on the specific case of the drainage area, the DT calculation period can be divided into days or hours. In each drainage stage, DT is divided, the drainage coefficient is calculated for a unit area (an area of 01 ha), determined on the basis of solving the water balance problem between input quantity and output quantity to Find the depth of the water layer that needs drainage to satisfy the drainage requirements of objects in the study basin:
+ The input quantity includes the amount of incoming water (amount of rainwater) during the calculation period and the amount of available water at the beginning of the calculation period.
+ The amount of output water includes the amount of water drained away, the amount of water lost during the calculation period and the amount of water remaining at the end of the calculation period.
- Calculating drainage regime of rainwater for drainage areas must comply with the principle: "bury water, spread water (disperse water) and drain water in a planned manner". The drainage coefficient calculation area must have a complete system of drainage and water regulation works (including field banks, canals, drainage culverts and works on drainage canals) from the focal point to the field surface.
- Depending on the water drainage requirements of each type of object present in the drainage area as well as the type of drainage rainfall model designed to be daily or hourly rain, the drainage coefficient calculated for each drainage object is the average drainage coefficient of the drainage area. per day, hourly average or average of a number of rainy hours during drainage. The design drainage coefficient of an area with many different water drainage objects is the average daily drainage coefficient with the largest value.
- Before proposing a solution to correct the drainage coefficient diagram of the area mentioned in 7.2, it is necessary to carefully investigate and study the field as well as the actual conditions of the drainage area to choose an appropriate solution. When choosing a solution to take advantage of the rice plant's ability to withstand flooding to store an additional layer of water that needs to be drained in the rice field or choose a solution to create a regulating pond to regulate the drainage coefficient, it is necessary to preliminarily determine the location and area of the rice field. Each type of soil can perform this task as well as the depth capable of storing and regulating water of each storage area.
- In the basin of a drainage headworks, many regulating lakes can be arranged, each lake is in charge of an independent basin (a drainage zone) located at the end of the canal to transfer water from the drainage zone to the water receiving drainage area. If only one regulating pond is arranged, the closer the pond is arranged to the location of the focal work, the greater the effectiveness of water regulation and reduction of drainage coefficient for the basin of the drainage work.
LawNet