昆明市城市绿地蓄水滞洪效益研究

城市绿地的蓄水滞洪效益是城市绿地水土保持效益的重要方面。以昆明市建成区城市绿地为研究对象,分析其蓄水滞洪效益,结果表明:绿地表层土壤总孔隙度较大,然而土壤稳渗率普遍较小,尤其是人工绿地,平均值只有0.242mm/min;在一年一遇1 h降雨(36 mm)条件下,除了自然绿地外,人工绿地均有径流产生,人工绿地平均蓄渗率只有15.10%;当前期非毛管孔隙没有水分滞存时,绿地的暂时滞洪效益非常显著,12.35 cm土壤即可蓄存全部降水;土壤稳渗情况下,绿化区平均下凹3.73 cm即可额外蓄渗非绿化区50%的径流;若要绿化区不产流,则绿地平均入渗率至少要达到0.6 mm/min或下凹2.1 cm。从降水特点分析,昆明市城市绿地目前滞洪效益较低,需要提高土壤入渗性能或建下凹式绿地。

Benefits of Water Accumulation and Flood Detention of Urban Green lands of Kunming

The benefits of water accumulation and flood detention of urban green lands are of an important aspect in urban water and soil conservation.The paper analyzed the benefits of water accumulation and flood detention by taking urban green lands of Jiancheng district of Kunming as a study object.The outcomes show that: a) the total porosity of surface soil is greater and the steady infiltration rate is smaller,especially the average steady infiltration rate of the planted green lands is only 0.242 mm/min;b) all the planted green lands have outflows under the conditions of rainfall in 1 hour(36 mm/h),which is 1-year frequency,except natural green lands.The average rainfall infiltration rate of planted green lands is only 15.10%;c) the benefits of flood detention in temporary of green lands are very obvious and the soil with 12.35 cm thickness can store all the rainfall,when there is no water stored in non-capillary pore during the earlier stage;d) under the conditions of stable infiltration,50% surface runoff of hardened surface can be absorbed when the greenland is 3.73 cm lower than that of the surrounding area and;e) if it requires the greenland has no surface runoff,the average infiltration rate of greenland should be reached to 0.6 mm/min at least or 2.1 cm lower than the surrounding area.At present,the benefits of flood detention of urban greenland in Kunming are lower based on the analysis of rainfall characteristics,and it needs to increase the capacity of infiltration rate and building low elevation green lands.