ObjectiveDue to the limitations of existing buildings, pipes and elevation difference and other basic conditions, the sponge transformation of urban built-up areas is a difficult point, especially in urban residential areas in alpine areas, which faces many practical problems and technical difficulties. Taking the Antaihuating Community in Xining City as an example, this paper introduces the sponge transformation design in detail, and verifies the effectiveness of the implementation, so as to provide case basis for the sponge city construction in such areas.

MethodBased on the analysis of site conditions, LID facility selection and layout, two SWMM models (before and after the sponge transformation) were established to simulate the runoff under 2 hours rainfall in different return periods (2, 5, 10, 20 and 50 years). At the same time, using the observed rainfall data to verify the validation of the model simulation.

Result(1) According to the current situation of the site, five kinds of LID facilities were introduced, namely rain garden, grassed swale, permeable pavement, roof garden and rainwater storage tank. (2) Comparing with the two SWMM models, the simulation data showed that under the conditions of 10, 20 and 50 years recurrence interval, in outlet C1, the peak discharge decreased by 83.45%, 79.31% and 57.39%, respectively. The peak flow time was delayed by 82 minutes, 40 minutes and 30 minutes. In outlet C3, the peak discharge decreased by 65.96%, 34.04% and 22.34%, respectively, the peak flow time was delayed by 65 minutes, 50 minutes and 62 minutes. After rebuilding, the discharge of drainage outlet in the recurrence interval of 50 years was lower than that of 2 years before the reconstruction. The flood control and drainage capacity of the community had been improved. (3) By comparing with the three actual rainfall and runoff data, it was found that the simulation data can match the actual monitoring data well, which shows that the parameter calibration of the SWMM model is reasonable and the simulation conclusion has a high credibility.

ConclusionRelative to the unimproved area, the production peak runoff discharge of the reconstructed area is greatly reduced, which fully illustrates that the implementation of LID design effectively reduces the discharge and achieves the comprehensive objectives of peak cutting, delay and decontamination.