Thesis study -- Analysis of the influence of rainfall field division method on rainfall control rate

Write it at the front ：《 Water supply and drainage in China 》; Chinese Core Journal ;

author ： Beijing Institute of water science and technology Zhang Yuhang 、 Yang Moyuan

1 Abstract

1. Annual total rainfall control rate , It is the main assessment index of sponge city construction ; therefore , Rainfall field division method is an important factor affecting the calculation of total rainfall control rate ;
2. The results show that ： Minimum rainfall interval , It is an important factor that affects the result of rainfall field division ;
3. As the minimum rainfall interval increases , Small rainfall events are combined with adjacent rainfall time , The frequency of moderate and heavy rainfall and the total amount of rainfall are increased ;
4. What is? “ Design rainfall ” ？ What is? “ Total runoff control rate ”？ Control rate of rainfall frequency ？

2 introduction

1. from 2014 year , Issued by the Ministry of housing and urban rural development 《 Technical guide for sponge city construction 》, take 【 Total runoff control 】 As the primary goal of rainwater system construction for low impact development in various regions , And will 【 Annual total runoff control rate 】 As the main assessment objective of sponge city .
2. 【 Annual total runoff control rate 】 amount to 【 Annual total rainfall control rate 】, By controlling the runoff generated by rainfall .
   

2.1 The division method of rainfall events

For a certain historical rainfall sequence , Different field division methods , Corresponding to different Design rainfall - Rainfall control rate curve .

• So , The point of this article is this , Study the method of rainfall time division , The law of influence on rainfall control rate , So as to reasonably calculate the rainfall control rate .

1、 Compared with daily rainfall data , The field rainfall data can better reflect the actual rainfall characteristics ;

2、 For a certain historical rainfall sequence , Planning of rainfall events
The method of classification is different , The division results are also different .

3、 At present, there are two commonly used rainfall field division methods in sponge city construction ： One is 《 guide 》 The number of daily rainfall used in According to the , namely 20 Till next day 20 Accumulated rainfall during the period ; Second, it is divided according to the actual rainfall process , The key is the minimum rainfall interval （T） Reasonable determination of .

4、 The daily rainfall data is used as the rainfall data of the event , It is a fixed partition method , There is a big deviation from the actual situation .

• Minimum rainfall interval before two rainfall events （T) It can be based on the emptying time of the facilities 、 Determination of factors such as the maximum concentration time of the basin .

• generally speaking , Urban watershed （ Drainage zoning ） The maximum concentration time of is 2h about , The ponding time of biological detention facilities shall not exceed 6h, The emptying time of rainwater infiltration facilities and wet ponds is 12h, The emptying time of the reservoir can reach 24h .

• Based on the above analysis , In order to fully compare the differences of rainfall field characteristics obtained by different division methods , It reflects the control rate of rainfall by different division results - Influence law of design rainfall relation , In this study T The value is 1,2, ..24 h .

• according to 《 guide 》 The requirements of , It is considered that the number of rainfall events ≤ 2mm Of （ Generally, there is no runoff ） Is invalid rainfall .
• From the picture 2 It can be seen that , When the minimum rainfall interval > 6h when , Its effect on the number of effective rainfall events is not significant .

3 The influence of minimum rainfall interval on rainfall control rate

• Well, there are some conclusions in the paper that are not easy to understand , Especially the control rate and so on .

4 Conclusions and recommendations

1. The minimum rainfall interval is an important factor affecting the results of rainfall field division , As the minimum rainfall interval increases , The small rainfall time is combined with the adjacent rainfall time , The frequency of moderate and heavy rainfall and the total amount of rainfall are increased .
2. a 《 guide 》 In terms of daily rainfall data selected from , The field rainfall data can better reflect the actual rainfall characteristics .