基于低影响开发的城市高密度区域雨洪蓄渗演化机理研究

The development of new urban zones and the expansion of related ceaselessly growing infrastructures have greatly increased impermeable, macadamized, hard, dry and inhospitable surfaces, and reduced the porous zones that naturally absorb rainwaters, which have modified the water cycle process irreversibly. It has increased peak flows generated by thunderstorms and heavy rains, clogging collections networks and increasing the runoff volume that flows into the waterways. This organization of the urban hydraulic networks has shown its limits and inability to contain the flow it is required to manage. In order to solve these problems, Low Impact Development (LID) or “sponge city” is put forward as one of the 100 major projects in the future of China. It is an innovative stormwater management approach which seeks to maintain or replicate the natural hydrologic patterns of urban sites, however, the applicability of the LID technologies learned from foreign experiences is not systematically recognized and evaluated, especially for urban high density area with relatively thin vadose zone. These problems are of importance and urgency to China. This proposed research project will select a typical high-intensity urban area in Shanghai as the research area. The mechanisms of stormwater infiltration and rainfall-runoff transformation will be considered systematically by multiple methodologies including field observation, physically-based model simulation and numerical simulation. The analytical model and mathematical expression proposed in this project provide important theoretical basis for the construction of LID urban stormwater management, and technically support construct the “sponge city” in China in the future.

城市化的快速发展造成了城市水文特性的改变，使得雨水滞留与调蓄功能下降，地表地下水相互作用更复杂，雨洪灾害日趋严重。为解决此问题，中国将建设海绵城市列为未来五年计划实施的100个重大项目之一。目前，参考国外经验的低影响开发技术，在国内的适用性特别是在高密度区域运用效果如何？地下水埋深与低影响开发措施相互影响如何？这已成为迫切需要解决的难题。本研究以上海城区内的典型高密度区域为研究区域，采用现场观测、物理模型试验和数值模拟等方法，系统开展城市高密度区域雨洪量响应、低影响开发关键影响因子研究，探索产流机制和地表地下水相互作用规律，改进低影响开发雨洪蓄渗数学模型，弥补原有模型未考虑地下水的缺陷，完善地表地下水相互作用下雨洪蓄渗演化的理论体系，解决低影响开发适用性数值模拟的关键技术问题。揭示基于低影响开发的城市高密度区域雨洪蓄渗演化机理。预期成果将为建设高密度区域海绵城市提供理论依据和技术支撑。

随着城市化进程不断加快，城市地区水问题日益突出，极端降雨易造成洪涝灾害，地表水体质量恶化。不同强度的雨洪作用下携带重金属污染物的地表水会经过土壤下渗到地下水中，对地下饮用水水质造成影响。探究城市高密度区域雨洪蓄渗过程中重金属污染物迁移演化机理对开展基于低影响开发技术的海绵城市建设、解决城市地区雨洪下渗造成的水安全问题具有重要意义。本项目以上海地区典型土壤地下水条件、重金属污染物为研究对象，采用现场取样、室内试验及数值模型等方法，开展了系统性的研究，旨在探明雨洪蓄渗过程中低影响开发关键因子，如胶体颗粒非吸附携带作用、矿物金属元素对重金属污染物的形态转化作用、地表地下水交互作用以及地下水含水层变渗透性等，对重金属污染物迁移演化的影响机理。主要研究内容包括：城市高密度区域地下水中重金属的吸附与运移特征研究；雨洪蓄渗过程中胶体-重金属的非吸附携带运移机理研究；土壤地下水中矿物金属元素对重金属形态转化影响的研究；地表地下水交互作用下重金属污染物赋存、运移与转化机理研究；EDTA促进地下水变渗透系统中重金属污染物运移的机理研究。通过研究，丰富了现有的土壤胶体-重金属协同迁移机理研究思路和内容；提出了低影响开发中可合理利用普遍存在的土壤矿物元素Fe(Ⅱ)对重金属污染物进行形态转化和削减；促进了对不同降雨强度下地表地下水交互作用的认识；建立了EDTA作用下重金属污染物在复杂变渗透系统中转化运移的数值模型。成果有利于为基于低影响开发的城市高密度区域海绵城市建设、土壤地下水重金属污染的预测和修复及水资源综合管理提供理论依据和技术支撑。