The guaranteed water level is mainly determined according to the engineering conditions, the national economic situation of the protected area, the flood characteristics and other factors. In practical work, the highest flood level in flood season over the years is often used in river control stations or important dike-crossing buildings. For example, the guaranteed water level at Hankou Station of the Yangtze River was 28.28m 1954 years ago, that is, the highest measured flood level of 193 1 year; After 1954, it is set to 29.73m, that is, the highest measured flood level is 1954.
Extended data:
The warning water level is analyzed according to the long-term flood control law, the importance of protected areas and the flood characteristics of rivers, and reported to the flood control department for approval. Ensure that the water level is higher than the warning water level, but lower than the designed maximum safe water level of the dike. It is the water level at which flood control works can ensure safe operation. The flood control department shall, according to the situation of river dikes, set the upper limit water level for flood control safety.
When the flood level is lower than or reaches this level, the flood control department should ensure the safety of the dike, so that the project is completely in a safe and defensive position in flood control scheme and flood control dispatching.
In wandering rivers, bank collapse may occur below the warning water level due to the fluctuation of river regime. The warning water level of dike protection areas in large rivers is usually set at the water level when floods generally overflow or important dike sections begin to overflow. At this time, the river section or area began to enter the state of flood prevention and alert, and relevant departments further implemented defensive posts, emergency materials preparation and other work, and stopped using cross-dike culverts.
The water level is mainly determined by the flood control department according to the long-term practical experience of flood control and the basic laws of dike and other projects. Rivers and lakes in China, represented by hydrological (water level) control stations, draw up warning water levels, which are approved and issued by higher authorities.
In order to ensure the safety of dikes, it is forbidden to use culverts and pumping stations on dikes, and to restrict or prohibit the passage of vehicles; Some embankment sections will also formulate relevant regulations according to the characteristics of embankment sections to ensure safety.
The guaranteed water level is generally based on the highest water level of a river, taking into account the upstream and downstream relations, tributary relations, the conditions of the actual highest water level in that year, the importance of protected areas and the national economy. , and make a comprehensive analysis and reasonable formulation, and obtain the approval of the higher authorities; In fact, the highest water level that a river has ever seen is often regarded as the guaranteed water level.
Ensure that the water level will change with the changes of river courses and dike projects, especially in sandy rivers, such as the lower reaches of the Yellow River. Due to sediment deposition, the riverbed is raised year by year, and the dike is heightened and reinforced, so it is necessary to raise the guaranteed water level accordingly. When raising the guaranteed water level, it is generally necessary to pass the economic and technical demonstration, then implement it and gradually improve it.
References:
Guaranteed water level _ Baidu Encyclopedia