Study On Index Decomposition Of Sponge City Based On Rainfall Runoff Balance Method ——A Case Study Of Kunming

Sponge City is an important part of infrastructure construction in China,its theoretical system is constantly improving.Sponge city is a complex system including planning,construction,operation and maintenance.The main line running through this system is the Volume Capture Ratio of Annual Rainfall（abbreviated as K value）.It can be considered that sponge city construction is a process of determining K value and decomposing K value.In sponge city planning,there exists the problem that of discontinuity of planning system and Sponge city index is not corresponding to urban planning.In the process of K value Index Division,it is decomposed directly into block on the basis of Master Plan or Special Plan,but not Regulatory Plan and Site Plan.The decomposition span is too large,and the cumulative deviation of subjective assignment is large,which affects the rationality of block index and the accessibility of target.Sponge city index Division is the Key to Sponge City Planning and Construction,the current method of K value decomposition is the method recommended by the code of Sponge City planning.But in theory and operation,it needs to be improved,which is reflected in the insufficient integration combination of calculation principle with geographical space and actual conditions,which will Cause the block to absorb too much rainfall runoff.This goes against the original purpose and not conducive to the living environment.At the same time,exceptionally cumbersome and inefficient calculation process makes the planning and design less operational.This paper constructs a multi-level Sponge City planning system,which Including master plan,special plan,Regulatory Plan and Site Plan,by taking Volume Capture Ratio of Annual Rainfall of Sponge City as Axis,Linking and Embedding Sponge City Construction and Urban Planning System at Macro,Medium and Micro Levels.This realizes the connecting link between different city planning in sponge city construction.This article establish a new method（Rainfall Runoff Balance Method）to composing K value and gives its specific details,including its mathematical model,calculation formula and operation guide.To contrast the advantages and disadvantages of the above new method and old method（The method recommended by the code of Sponge City planning）,this paper takes Cao Hai Zone of Kunming as a Sponge City planning case.The results show that the new method is more in line with the characteristics of regional rainfall,fully respecting the characteristics of the block itself.