Various problems such as urban flood inundation and water shortage occurred in China during the rapid urbanization in the last several decades. An urban water management program called Sponge City (SPC) is put forward in China in 2014 in order to relieve the flood inundation and water shortage situation. The SPC program implements not only the concept and practices of low impact development but also various comprehensive urban water management strategies. The SPC development promotes water security, water environmental protection, and water ecological restoration. The background information and general principles of the SPC program are introduced in this paper as well as the experience and achievement obtained in developing SPC so far. Sixteen cities have been selected by Chinese government as SPC’s pilot cities in March, 2015. The Chinese government will provide special subsidy and financial support for the development of SPC in the next three years. The geographic, hydrologic, economical characteristics of the sixteen cities vary from each other, therefore, the SPC plan and implementation will be different in 16 cities. A new investment and financial supporting mode based on public-private partnership concept is employed to handle the SPC construction and operation cost. Chinese central and local government agencies and engineers are exploring various innovative methods to handle the problems caused by rapid urbanization as well as seek sustainable financial support and investment approaches for urban infrastructure construction related to SPC development.

The particle tracking method (PTM) module was added into the open source Full Shallow-Water equations for Overland Flow in a two-dimensional (FullSWOF_2D) program, which has coupled rainfall–runoff and infiltration modules to determine the time of concentration (T_c) for impervious (T_ci) and pervious (T_cp) surfaces. The updated program FullSWOF-PTM was tested using observed rainfall events with Nash–Sutcliffe efficiencies ranging from 0.60 to 0.95 (average of 0.75) for simulated runoff hydrographs. More than 400 impervious modeling cases with different surface slope (S₀), roughness coefficient (n), length (L), and rainfall intensity (i) combinations were developed and simulated to obtain the T_ci for developing the regression equation of T_ci as a function of the four input parameters. More than 700 pervious modeling cases with different combinations of S₀, n, L, i, and infiltration parameters including the saturated hydraulic conductivity, suction head, and moisture deficit were simulated to estimate the T_cp based on the travel time of 85% of particles arriving at the outlet and the ponding time. The regression equation of T_cp was developed as the sum of T_ci and additional travel time as a function of infiltration parameters and i. The T_cp equation can be applied to wide ranges of input parameters in comparison to Akan’s equation.

Source facilities can manage stormwater runoff pollutants while also limiting runoff volume in China’s sponge city construction. However, there is no apparent link between source volume control and runoff pollution reduction. This research uses SWMM to develop a model based on the basic data of a city’s catchment zone in northern China in order to statistically examine the response relationship between the initial runoff volume capture of sponge city construction and the reduction effect of stormwater runoff pollution. Based on the dimensionless constant of the runoff pollution control curve, we suggested a novel approach for evaluating runoff pollution control effectiveness. This method was used to examine the response relationship between runoff volume control and runoff pollution control in three typical initial runoff volume capture facilities in the study area, namely bioretention, permeable pavement, rain barrels, and terminal storage tanks, under various design rainfall conditions. The dimensionless constant (Dc) has good practical application value and can quantitatively quantify the control effect of various facilities on stormwater runoff pollution. The Dc value of the source facilities is higher than that of the terminal control facilities, indicating that the source facilities have a higher ability to reduce rainwater runoff pollution than the terminal facilities, particularly the infiltration facilities. The research ideas and evaluation methods proposed in this paper provide an alternative approach for selecting and optimizing facilities during the planning and designing stages of sponge city construction, which can also be used in the monitoring and evaluation stage after completion to carry out a more effective evaluation of sponge facilities’ effects.