【作者】 程江；

【导师】 杨凯；

【作者基本信息】 华东师范大学 ， 环境科学， 2007， 博士

【摘要】 土地利用/土地覆被变化(LUCC)研究是目前全球变化研究的前沿和热点课题。快速城市化导致城市规模不断地扩张,高强度人类活动剧烈改变城市土地利用/土地覆被类型,形成不同于自然地表的“城市第二自然格局”,对城市地表水文过程产生深刻影响。城市LUCC水文响应是体现人类活动对城市水文循环影响的理想研究对象。论文选择位于中国东部平原河网地区的上海中心城区为研究区域,从环境学、生态学及水文学的交叉视角,采用理论与实践结合、定性和定量分析相结合的方法,以城市化地区长时间尺度LUCC特征和演变过程研究为切入点,围绕LUCC导致的水量和水质效应两条主线,探讨了上海中心城区LUCC的环境水文效应,并尝试构建了基于“生态排水”理念的城市化地区土地利用/土地覆被类型的优化策略。论文主要研究结论体现在以下四个方面。(1)上海市中心城区50余年来,主导土地利用类型经历了一个从水域(包含农田)、城市住宅用地和道路广场用地逐步向城市住宅用地、工业用地和绿化用地转化的多变过程,土地利用结构逐渐向均衡状态发展,各土地利用类型的面积差别减小,土地利用结构均质性增强。对小尺度城市汇水域的案例分析表明,随着城市化过程的发展,受人类活动影响,小尺度城市汇水域的LUCC过程存在较大分异,对城市水文过程产生深刻影响。中心城区50余年来水域面积大量减少导致区域生态服务功能显著下降,经济持续发展、城市建设加速与人口增长是主要驱动力。(2)从区域河网水系演变、土壤含水率与持水能力、土壤稳定入渗速率、降雨径流过程等层面深入探讨了LUCC对上海中心城区水文过程的影响机制。研究显示:①受人类活动显著影响,50余年来中心城区LUCC导致大量河道阶段性集中被填没,使得中心城区河流水系分枝比锐减、水系结构破坏、河网水系分维数异常,河道槽蓄容量较50余年前减少超过70%,河网水系调蓄能力削弱加大了区域防洪排涝压力;②土地利用/土地覆被类型与高程对土壤含水率、土壤调蓄降雨径流能力影响显著,有覆被植物土壤含水率绝大部分超过无覆被植物的裸土,低势草坪(下凹式绿地)土壤含水率和调蓄降雨径流的能力均优于高势绿地和普通高程绿地;③土地利用方式、覆被类型和土壤表层结皮是不同类型绿地土壤稳定入渗速率存在显著差异的主要影响因素。④LUCC对中心城区降雨径流过程影响深刻,导致2000年至2003年径流系数有增加趋势。由于土地利用类型差异,在城市LUCC过程中,小尺度城市汇水域的土地利用类型变化存在显著差异,导致汇水域内降雨径流过程的存在较大差异。以绿化覆盖率分别为39.13%和27.36%的对照研究组为例,增加约10%的绿化覆盖率能对削减城市降雨径流总量和延时降雨径流洪峰产生较明显效应。⑤下凹式绿地和多功能水绿复合调蓄系统具有显著的环境水文效应。在适宜土壤稳定入渗速率(5.0×10-7～5.0×10-5m/s),修建适当下凹深度(0.1～0.3 m)、面积比例(10～30%)的下凹式绿地可以基本削减3年一遇设计暴雨重现期,连续1 h降雨产生的地表径流。结合上海市多年降雨特点、区域土壤稳定入渗速率以及城市绿化覆盖率现状的分析显示,在上海中心城区和新城市化区域新建或改建适当比例的下凹式绿地具有理论上的可行性。对设定边界条件的城市多功能水绿复合调蓄系统的雨水径流蓄渗能力计算亦表明其具有良好的环境水文效应。(3)上海中心城区不同土地利用/土地覆被类型的降雨径流非点源污染具有强烈的时空分异特性,TSS和CODCr是降雨径流中的主要污染物质。中心城区降雨径流非点源污染存在明显初期效应,是造成雨后城区地表水体遭受冲击性污染的主要原因。室内外不同土地利用/土地覆被类型削减降雨径流污染物的实验表明,城市绿地具有显著的削减降雨地表径流污染物的效应:①室内有覆被植物和无覆被植物两种条件下,土壤含水层处理系统削减降雨地表径流污染物的实验结果表明,在论文限定的实验边界条件下,高度1 m左右的土壤柱对服务面积1.09～2.75倍于绿地面积汇水域内,在设计暴雨重现期为0.5年、1年、3年和5年,连续降雨1 h条件下形成的低、中和高污染物浓度的城市降雨径流具有良好的削减效应,CODCr、NH3-N和TP总体平均削减率分别达到35.27%、60.12%和65.37%。土地覆被、污染物浓度、土层厚度以及水力停留时间是影响土壤含水层处理系统运行效率的主要因子。②室外覆被植物土地对降雨地表径流污染物的削减实验表明,CODCr、NH3-N和TP平均削减率分别达到52.21%、48.98%和47.35%,较室内有覆被植物土壤含水层处理系统CODCr削减率提高约20%,NH3-N和TP分别下降约10%和16%。由于降雨径流进入绿地后水力停留时间较短,导致CODCr、NH3-N和TP的去除机理主要是渗滤介质的机械过滤与吸附等物理作用,上述物理作用与微生物较弱的降解作用共同造成室外CODCr、NH3-N和TP的削减规律符合一级反应动力学模式,污染物进水浓度对其削减率的影响不显著。降雨强度对污染物削减效率有一定影响,具体表现为小雨和中雨的污染物削减率要高于大雨时。(4)基于德国、美国和日本等城市降雨径流利用和管理经验,从降雨径流“零增长”和径流污染物“减量化”两个角度提出了城市降雨径流“生态排水”理念,强调采取工程性与非工程管理性措施相结合的方法,尽可能增加城市降雨径流就地入渗量、削减径流污染物,以“生态排水”的方式达到维持城市水文过程良性循环的目的。基于城市“生态排水”理念,以优化城市土地利用/土地覆被类型和格局为基础,从削减水量和控制水质两个层面构建了城市“生态排水”的最佳管理措施,通过生态化、非工程强排水型措施促进城市降雨径流生态型排水。尝试构建了以法律法规政策的保障机制、经济杠杆的激励机制、技术手段的运用机制和管理制度的调控机制为主体框架的“生态排水”型城市雨水资源综合利用体系。更多还原

【Abstract】 Land use and land cover change （LUCC） research was one of advance and hot area of the global change researches. Fast development of urbanization lead to continuous expansion of city size, and high-intensity human activity changed land use and land cover type greatly. Hydrology process was changed dramaticly by the second nature setup in city which was different to nature ground surface. So hydrology response to LUCC caused by human activity became a better research subject. Baesd on the cross subjects of environmental science, ecology and hydrology, revolved around two points （hydrology effects due to LUCC and runoff pollution reduceing）, both theoretical and practical aspects related to environmental hydrology effects due to LUCC in the center urban of Shanghai were discussed, and an optimum adjustable strategy of land use and land cover type in city was rebuilt based on the conception of ecological drains. The main research conclusions of this paper were summarized as follows:（1） During rescent 50 years in center urban of Shanghai, the main land use types changed from water （include farm field）, urban residential area and road to urban residential area, industrial land and green area. The decreasing of area diffence among different land use types resulted land use structure became more equilibria. The typical case study showed that because the human activity, there were great differentiation in the process of LUCC in small urban catchment. The differentiation would cause profound effects on urban surface hydrology. The reason of ecological services failed down greatly was water area disappearing largely, which was caused by economic development, urban construction and population growth..（2） On the research viewes of river system change, soil water content and water holding capacity, soil stable infiltration rates and rainfall-runoff process, hydrology effects due to LUCC were discussed. The results were showed as follows:① In the past 50 years, a large number of rivers disappeared centrally during several phases, which was casued by human activity, that lead to river system structure destroyed greatly. High urbanization lessened the branching ratio, which resulted to an abnormal fractal dimension. The total river storage capacity reduced over 70 % compare with the storage capacity of 50 years ago, so the ability of water storage capacity was greatly weakened and flood prevention pressure was also increased in the center urban of Shanghai.② Land use and land cover type, and land elevatioin affected soil water content and water holding capacity effectively. Water content and water holding capacity of soil with vegetation cover were greater than those without cover, and sunken green space has better storage capacity than high elevatioin and general elevatioin green space.③ Land use type, land vegetation cover type and soil surface crust affected soil stable infiltration rates significantly.④ LUCC impact rainfall-runoff process deeply, fast urbanization process resulted an increasing tendency in runoff coefficient. Taking two adjacent small urban catchments as a study case, there were significant differences in the change of land use type between the two catchments in the urbanization process because of the different land use structure in small scale area, which caused the variation of runoff storage capacity between the two drainage systems. The green space had significant storage effect on city runoff. Adding 10 % green space land would result considerable effects of runoff storage and increase time-lag between precipitation and runoff flood reaching time.⑤ Sunken green space and multifunction green-water space compound system were some of the useful ecological drains facility with powerful rainwater capacity, which had good environmental hydrology effects through storing and infiltrating more rainwater. Under general case, with area ratio from 10% to 30%, sunken depth from 0.10 m to 0.30 m and soil stable infiltration rate from 5.0×10^-7 to 5.0×10^-5 m/s, sunken green space can store and infiltrate one hour continues precipitation at three years rainfall recurrence interval. Based on the analysis of the secular precipitation, soil stable infiltration rate and present urban green open space area in the center urban of Shanghai, sunked green space could be built in proper areas of center urban and developing urbanization area. Through the calculation, it was got that green-water space compound system had fine rainwater capacity.（3） There existed significant temporal and spatial variation in rainfall-runoff non-point pollution in center urban of Shanghai, TSS and COD_Cr were the main pollution of rainfall-runoff. The significant first flush phenomenon resulted in great impact deterioration of the quality of urban receiving water. The experiments of inside and outside with different land use and land cover typies showed that urban green open space had notable effect on decreasing contaminant of runoff. Inside experiment showed that a soil aquifer treatment with or without vegetation cover, the average COD_Cr、 NH₃-N and TP remove rate of low, middle and high pollutant concentrations were 35.27 %、 60.12 % and 65.37 %, respectively. Those influencing factors to pollutant remove rate were land cover, pollutant concentration, thickness of soil layer and hydraulic retention time. Outside experiment showed the average COD_Cr、 NH₃-N and TP remove rate of representative green open space were 52.21%、 48.98 % and 47.35%, respectively. Comparing to those of inside experiment, COD_Cr romove rate increased about 20%, romove rates of NH₃-N and TP decreased about 10 % and 16 %, respectively. Because of the short hydraulic retention time, the main pollutant remove mechanics was related to mechanical filtering and physical absorption by soil, and micro-biological degradation could be ignored, so the pollutant remove rate model could agree with first reaction kinetics model. Experiments also showed that pollutant remove rate decreases with increasing of rainfall intensity.（4） Depending on advanced experiences of rainwater resource utilization and management of Germany, USA and Japan, ecological drains conception was structured through two aspects, which were zero growth of rainfall-runoff and runoff pollutant decrease. In order to realize optimal urban hydrologic cycle, the ecological drains conception required increasing runoff infiltration and decreasing runoff pollutant through engineering technical facilities and non-engineering management measures. Based on optimal urban land use and land cover type, best management practices of ecological drains were formed through decreasing runoff and remove pollutand. Four inspirations of set up urban rainwater resource utilization and management system were gained. The first is to establish nationwide law and rule to guarantee rainwater resource use, the second is to support development of rainwater resource utilization technology to promoting use of rainwater resource, the third is to use establish economic adjust and control means to motivate rainwater resource use, the fourth is to establish uniform specialized functional management department to norm rainwater resource utilization.更多还原