Development of Seepage-Type Detention Facilities for the Control of Urban Runoff

本文阐明了入渗型截留设施在城市水文中的作用。在此基础上，提出了考虑多层地下结构组合的城市径流定量控制措施。基于孔隙中水柱的流体力学，建立了非饱和渗流的理论模型。建立了均匀管和变截面管的毛细管模型，推导出了渗透率随含水率的函数和渗透率与压力势的关系。理论估计与现有的观测结果或经验公式相当吻合。综合分析了由河道、拦阻设施和透水管网组成的水网通过改善地下结构进行防洪的措施。结果表明，通过管网和明渠的蓄能效应实现了峰值流量和峰值时间的减小。当我们在远离河道的地方建造入渗区或补给区时，地下水径流量没有明显增加。研究还发现，在高原地区建设快干基质对减少地表径流和地下水径流的峰值流量都是有效的。通过现场观测，估算了沟渠和透水路面的入渗能力。数学模拟与观测结果吻合得很好。

In the present study the role of infiltration-type detention facilities in urban hydrology was clarified. Furthermore, a quantitative and controlling measure was derived for urban runoff considering a combination of multi-layer subsurface structures.A theoretical model for the mechanics of unsaturated infiltration was developed based on hydrodynamics of water column in pores. A capillary model of uniform tube or varying-section tube was formulated which resulted in a theoretical derivation of permeability as a function of moisture content and a relationship between permeability and pressure potential. Theoretical estimation agreed quite well with existing observed results or empirical formulae.Flood control measures by the improvement of subsurface structures were comprehensively analyzed for a network which included channels, detention facilities, and pervious pipe networks. It is shown that the reduction of peak discharge and time to peak is accomplished by the storage effect in pipe network and open channels. When we construct infiltration area or recharge area away from river channels, no appreciable increase was observed in groundwater runoff. It is also found out that the construction of fast drying substrata in a plateau area is effective to reduce thepeak discharge both in surface runoff and groundwater runoff.Capacity of infiltration was estimated for a trench and a pervious pavement through field observation. A mathematical simulation reproduced good agreement with observed results.