基于城市洪涝径流和积水特征的绿色屋顶空间布局优化研究

Uurban flood runoff and waterlogging characteristics-based study on optimization of green roofs spatial layout

【目的】绿色屋顶等LID设施的空间布局差异会对城市洪涝灾害的削减效果产生不同的影响。为解决绿色屋顶在城市规划中具体空间形态的优化问题,【方法】通过设置随机分布、沿道路分布和沿积水点分布等3种绿色屋顶空间布局方案,利用SWMM模拟其对洪涝径流和积水特征的影响,并利用熵权-TOPSIS法综合评价出最优方案,实现绿色屋顶的空间布局优化。【结果】结果显示:(1)在相同绿色屋顶覆盖率下,不同空间布局的绿色屋顶对地表径流都具有较好的削减作用,对径流总量和峰值的最大削减率能够达到23.99%和39.12%。(2)不同空间布局对洪涝积水的影响差异明显,其中沿积水点分布布局的削减效果总体上要优于其他方案,该方案平均积水时间最多削减15.18%,积水节点最多减少69.19%,最长积水时间最多缩短10.98%,严重积水节点最多减少48.08%。(3)沿积水点分布布局的TOPSIS评分在多种情景下的总得分分别为0.663、0.685、0.526和0.594,均为得分最高的方案。【结论】结果表明:不同空间布局的绿色屋顶方案对地表径流总量的影响差距不明显,差值在2%以内,难以据此进行布局优化;凭借空间位置差异,沿积水点分布布局对洪涝积水的削减效果明显优于其他方案,在相同绿色屋顶覆盖率情况下能够更好地减弱洪涝的不良影响;沿积水点分布布局可以作为研究区绿色屋顶布局规划的参考方案,具有研究区类似下垫面特征和城市建设规划的地区,在开始进行绿色屋顶铺设时,可以优先在积水严重区域布设,形成沿积水点分布的空间布局,获取较好的洪涝削减效果,后续规划时再向其他区域扩张。

[Objective]The spatial layout difference of LID facilities such as green roofs will have different impacts on the reduction effect of urban flood disasters.In order to solve the problem of optimizing the specific spatial form of green roofs in urban planning,[Methods]SWMM is used to simulate their impacts on flood runoff and ponding characteristics by setting three spatial layout schemes of green roofs,namely,random distribution,distribution along the road and distribution along the ponding points,and entropy weight TOPSIS method is used to comprehensively evaluate the optimal scheme to realize the spatial layout optimization of green roofs.[Results]The results show that:(1)Under the same green roof coverage,green roofs with different spatial layouts can well reduce surface runoff,and the maximum reduction rates of total runoff and peak runoff can reach 23.99%and 39.12%.(2)The influence of different spatial layout on the characteristics of flood waterlogging is obvious,and the reduction effect of the layout along the ponding points distribution is generally better than other schemes.The average waterlogging time of this scheme is reduced by 15.18%at most,the number of waterlogging nodes is reduced by 69.19%at most,the longest waterlogging time is shortened by 10.98%at most,and the number of severe waterlogging nodes is reduced by 48.08%at most.(3)The TOPSIS scores of the layout along the ponding points distribution are 0.663,0.685,0.526 and 0.594 respectively,which are the highest under various scenarios.[Conclusion]The difference of three green roof schemes′reduction on the total surface runoff is not obvious,which is within 2%.So,it′s difficult to optimize the layout according to this.By virtue of the spatial location difference,the reduction effect of the layout along the ponding points on the flood and waterlogging is significantly better than other schemes,and the adverse impact of flood can be better reduced under the same green roof coverage rate.The layout along the ponding points can be used as a reference plan for the construction of green roof in the study area.For areas with similar underlying surface characteristics and urban construction planning in the study area,when green roof laying is started,priority can be given to laying in areas with serious ponding,forming a spatial layout along the ponding points to obtain better flood reduction effect,and then expanding to other areas in the subsequent planning.The spatial layout difference of LID(low impact development)facilities such as green roofs has different impacts on the reduction effect of urban flood disasters.Aiming at the optimization of the specific spatial form of green roofs in urban planning,its influence on flood runoff and waterlogging characteristics is simulated with SWMM(storm water management model)through setting three spatial layout schemes of green roofs,i.e.random distribution,distribution along road and distribution along waterlogging points,while the optimal scheme is comprehensively assessed out with entropy weight TOPSIS method,and then the spatial layout optimization of green roofs is realized.The results show that(1)under the same covering rate of green roof,all the green roofs with different spatial layouts have better effect to reduce surface runoff,from which the maximum reduction rate of total runoff and peak runoff can reach 23.99%and 39.12%respectively,while the reduction effect from the layout on the distribution along waterlogging points is weaker than those of the other two layouts,but the difference is not so obvious with the difference value within 2%,thus it is difficult to optimize the layout according to this;(2)the difference of the influence from different spatial layout on flood-waterlogging is obvious,in which the reduction effect from the layout of the distribution along waterlogging points is generally better than those from the other schemes.Under this scheme,the mean waterlogging time can be reduced by 15.18%at most along with the reduction of waterlogging points up to 69.19%,the maximum cutting down of the longest waterlogging time up to 10.98%and the maximum reduction of the serious waterlogging points up to 48.08%;(3)all the total scores of the layout of the distribution along waterlogging points under various scenarios are the highest,i.e.0.663,0.685,0.526 and 0.594 respectively,and then can be taken as the reference scheme for the planning of the layout of green roofs within the study area.For the areas with both the underlying surface features and the urban construction planning similar to the study area,the laying of green roofs can be preferentially carried out within the areas with serious waterlogging at the beginning of it,so as to form a spatial distribution along waterlogging points for getting better effect to reduce flood-waterlogging and expanding to the other areas in the subsequent planning concerned.