福州海绵城市建设中屋顶绿化的截水作用研究

Study of water storage effect of roof greening in the construction of Fuzhou sponge city

城市屋顶绿化具有截留水分、改善生态环境等作用,可作为海绵城市建设的重要内容。以福州市的鼓楼、台江和仓山3区为研究对象,选取Landsat8 OLI遥感影像为主要数据,基于连续最大角凸锥(sequential maximum angle convex cone,SMACC)方法提取屋顶绿化率,建立其与全局植被湿度指数(global vegetation moisture index,GVMI)的关系模型,并对屋顶绿化率进行模拟与分析。结果显示,福州市3区屋顶绿化率总体较低,平均值仅17.34%,绿化率为10%~20%的比例为66.55%,而绿化率高于50%的仅占5.11%;绿化率不同,湿度亦有变化,表明屋顶植被具备不可忽视的截水能力。通过构建屋顶湿度h与绿化率r的关系模型发现二次曲线模型拟合优度最佳;当屋顶绿化率高于16.30%时,截水效果开始明显;而在绿化率从30%升至60%过程中,截水能力提高速率最快,平均可达57.9%。选取2个典型小区对屋顶绿化率进行模拟分析,进一步证明该模型的合理性。研究成果证实了屋顶绿化的截水功能,并确定了截水目标下的屋顶绿化率阈值,可为海绵城市建设提供重要参考。

The urban roof greening has the effects such as water interception and ecological environment improvement,and can be an important part of sponge city construction. Taking Gulou,Taijiang,Cangshan Districts of Fuzhou City as the study objects and the remote sensing image of Landsat8 OLI as the main data,the authors extracted the roof greening rate based on sequential maximum angle convex cone（ SMACC）,constructed the relational models of roof greening rate and global vegetation moisture index（ GVMI） humidity indicator,and then simulated and analyzed the roof greening rates. The results show that the roof greening rate in the three districts of Fuzhou is overall low,with an average of only 17. 34%; the proportion of greening rate of 10% ~ 20% is 66. 55%,and only 5. 11% is higher than 50%. The greening rates are different,and there are also changes in humidity,indicating that the roof vegetation has remarkable water interception capacity. The quadratic fumction model of roof humidity h and greening rate r is the optimization model. When the roof greening rate is higher than 16. 30%,the intercepting effect begins to be obvious. In the process of greening rate increasing from 30% to 60%,the increasing speed of intercepting capacity becomes the fastest,with an average of up to 57. 9%. Two typical blocks were selected and the roof greening rates were simulated and analyzed,which further proves the rationality of the above model. The result confirms the intercepting capacity of roof greening and determines the roof greening threshold under the target of water interception,which provides important reference for sponge city construction.