Study on Hydrologic Performance Evaluation of Green Roof System with Storm Green Roof Response (SGRR) Model

Abstract

Until now, hydrological aspect of the green roof system has not been well known due to the focused attention to its aesthetic and thermal effects. However, since the limitation of the infrastructure expansion to the flood that occurred in the center of the big cities, green roof arose as an alternative solution. But, the absences of the evaluation method for the green roof systems hydrological performance as well as a clear standard from green building certification program give the difficulties to the quantifying the effect and proper application of the system.

Thus, the evaluation technique of the hydrologic performance of green roof system was developed in this research, and this technique laid the foundation of objective comparison and proposal of optimum green roof system by evaluating performance quantitatively. First, the performance evaluation factors were developed by analyzing hydrologic mass balance of green roof system. In this situation, the standards of performance evaluation are the flood mitigation effect and water resource management effect. The flood mitigation is evaluated by peak flow reduction ratio and peak flow time delay factors, and the water resource management is evaluated by total retention factor. This makes the reasonable evaluation of hydrologic performance of green roof system and the evaluation factors has reliability by the possibility of equivalent application at different climate and rainfall condition.

On the basis of Lab & Field scale experiment applied performance evaluation factor developed in this study, Analysis of experimental group performance about evaluation item and performance difference depending on natural and material conditions was investigated. From that test, Investigation about possibility of Green roof system performance evaluation depending on different type of green roof on basis of same performance evaluation factor. and then, Performance analysis about material conditions (soil, vegetation, drain board), natural conditions (rainfall, evapotranspiration) was analysed. Finally, Storm Green Roof Response (SGRR) Model simulated the runoff of green roof system was used for evaluating the performance by applying developed factors. Then it was estimated the possibility for the performance evaluating model. This model simulates runoff quantity by using Modified Pul's Method from inflow and out flow relationship equation. The material conditions like soil and plants are possible to modify easily but the evapotranspiration amount is the natural condition and difficult to get the data normally, so the model is calibrated based on the measuring evapotranspiration data from Seoul National University No. 35. This model shows that high similarity between modeling result and experimental result at performance evaluation. So It is considered that being adaptable to hydrologic performance evaluation of green roof system.