• 山洪/泥石流灾害监测技术与方法 •

### 基于洪峰模数的山洪灾害雨量预警指标研究

1. 1. 中国水利水电科学研究院,北京 100038
2. 水利部防洪抗旱减灾工程技术研究中心,北京 100038
• 收稿日期:2017-07-12 修回日期:2017-08-25 出版日期:2017-12-25 发布日期:2017-12-25
• 作者简介:

作者简介：李青（1982-）,女,山西静乐人,硕士,工程师,主要从事山洪灾害预警技术方面研究。E-mail: liqing@iwhr.com

• 基金资助:
云南省山洪灾害防治预警指标和阈值分析方法研究（JZ02032A032015）;全国山洪灾害防治项目（126301001000 150068）

### Rainfall Threshold for Flash Flood Early Warning Based on Flood Peak Modulus

LI Qing*(), WANG Yali, LI Haichen, ZHANG Miao, LI Changzhi, CHEN Xing

1. 1. China Institute of Water Resources and Hydropower Research, Beijing 100038, China
2. Research Center on Flood and Drought Disaster Reduction of the Ministry of Water Resources, Beijing 100038, China
• Received:2017-07-12 Revised:2017-08-25 Online:2017-12-25 Published:2017-12-25
• Contact: LI Qing E-mail:liqing@iwhr.com

Abstract:

Flash flood early warning is an important non-structural measure for flash flood prevention in China. Also, rainfall threshold is the key for flash flood early warning. At present, the method of calculating rainfall thresholds need a large amount of meteorological and hydrological data. Meanwhile, building the hydrological model and calibrating parameters are difficult, which are not suitable for the flood control personnel. A simple and easy method, using flood peak modulus to calculate rainfall threshold, was proposed in this study based on national flash flood investigation and evaluation results. Rational equation is the basis of the calculation method. The flood peak modulus in rational equation is expressed as a ratio of the flow to watershed area. Then, the critical rainfall formula is obtained. Using the Manning formula and national investigation and evaluation results, the flood peak modulus on the condition of critical flow is obtained, and the net rainfall is calculated. Based on the research results of the scholars, three aspects about the rainfall loss calculation are considered. They are depression storage, vegetation interception and soil infiltration. The sum of the net rainfall and the rainfall loss is the critical rainfall. Considering the factors such as soil water content of watershed, the rainfall threshold was finally obtained. In order to demonstrate this method, Shuanghe catchment in Suijiang County of Yunnan Province was chosen as the study area, of which the area is 89.12 km2. The calculated concentration time was 5.2 h. Thus, the duration was estimated to be 1 h, 3 h, and 6 h. The results indicated there was a linear correlation between the net rain amount and different rainfall durations. Depression storage and canopy interception was invariant during different rainfall durations, but the infiltration was variable. For 1 h duration, initial infiltration was the main factor to consider; for 3 h, both initial infiltration and mid-term infiltration were considered; and for 6 h, steady infiltration also needed consideration besides the initial and medium-term infiltration. The calculated critical rainfall for 1 h, 3 h, and 6 h were 38.6 mm, 64.8 mm, and 96.9 mm, respectively. Rainfall thresholds of different durations for flash flood early warning were estimated on basis of critical rainfall considering three different soil moisture conditions. Under dry soil moisture condition, large rainfall loss leads to a large rainfall threshold; under wet soil moisture condition, contrary to the dry condition, small rainfall threshold is caused by small rainfall loss; and under medium soil moisture condition, the rainfall threshold was in medium. The rationality analysis on critical runoff, rainfall losses, and rainfall threshold was carried out in the end of this study. The results showed the calculated rainfall threshold by flood peak modulus method was approximated to the rainfall threshold obtained from national flash flood investigation and evaluation project. Also, they are in accord with the observed rainfall during flash flood events. Thus, the calculated results are reasonable in this study. This study provided a quick and convenient way of calculating rainfall threshold of flash flood warning for the grass root staffs and offered technical support for estimating rainfall threshold correctly.