QX/T 451-2018 in English
VALIDMeteorological risk warning levels of small and medium-sized rivers flood induced by torrential rain
- Issued on:2018-11-30
- Implemented on:2019-03-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
$243.00
| Standard No: | QX/T 451-2018 |
| Document status: | VALID |
| Title in English: | Meteorological risk warning levels of small and medium-sized rivers flood induced by torrential rain |
| Title in Chinese: | 暴雨诱发的中小河流洪水气象风险预警等级 |
| Language: | English |
| File Format: | Electronic (PDF) |
| Delivery: | Via email within 1~3 business days |
| Issued on: | 2018-11-30 |
| Implemented on: | 2019-03-01 |
| Professional Classification: | QX-Meteorology |
| Related Keywords: | high water level rivers
flood level ≥design early warning level systems river water level ≥overbank water level |
| Related Topics: | flood
early warning Standard warning www+ Classification of small and medium water conservancy rivers Classification of large, medium and small rivers |
Introduction
Interpretation of the core content of the standard
This standard innovatively establishes a four-level early warning system based on the dynamic critical surface rainfall threshold, and realizes quantitative risk assessment through the coupling analysis of watershed soil moisture content and surface rainfall forecast value.
Comparison of early warning level systems
| River type | Level I (red) | Level II (orange) | Level III (yellow) | Level IV (blue) |
|---|---|---|---|---|
| Rivers excluding reservoirs | ≥overbank water level | ≥guaranteed water level | ≥warning water level | near warning water level (0.5m) |
| Rivers including reservoirs | ≥overbank water level | ≥calibrated flood level | ≥design flood level | ≥flood control high water level |
| Rivers without eigenvalues | ≥50-year return period | 20-50-year return period | 5-20-year return period | Close to 5-year return period |
Key Technology Implementation Path
Dynamic Threshold Derivation Method
The relationship between soil moisture and critical surface rainfall is established using the nonlinear discriminant function (Formula A.1):
d(z) = w₁zᵃ + w₂
Taking the Tunxi River Basin in Anhui Province as an example, its 24-hour Level III threshold function is: y = -211.83x⁰·⁷¹ + 320
Data-free watershed processing
Use watershed parameter transplantation formula (A.3):
Pₜ = b₁Aᵇ²Sₗᵇ³Lᵇ⁴Sᵢᵇ⁵
Threshold value estimation is achieved by comprehensively considering five types of geographical parameters, including catchment area, slope, and land use.
Business Implementation Suggestions
- Give priority to establishing a parameter library for the watershed hydrological model to achieve differentiated processing for watersheds with different data completeness.
- Warning issuance needs to be combined with the GIS system to display the hierarchical visualization of the RGB color scale (255,0,0)-(0,102,255).
- For rivers with no characteristic values, it is recommended to supplement historical flood surveys and improve the return period benchmark data.
Standard Evolution Analysis
Compared with the 2013 version of the trial specification, this standard has the following major breakthroughs:
- For the first time, the distinction between overbank water level and overdam water level is clearly defined.
- The concept of dynamic critical surface rainfall is introduced to replace the original fixed threshold method.
- Added parameter migration technology path for watersheds without data
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