Performance assessment of extensive green roof runoff flow and quality control capacity based on pilot experiments

Yongwei Gong; Dingkun Yin; Junqi Li; Xianwei Zhang; Wenhai Wang; Xing Fang; Honghong Shi; Qi Wang

doi:10.1016/j.scitotenv.2019.06.100

Performance assessment of extensive green roof runoff flow and quality control capacity based on pilot experiments

Sci Total Environ. 2019 Oct 15:687:505-515. doi: 10.1016/j.scitotenv.2019.06.100. Epub 2019 Jun 11.

Authors

Yongwei Gong¹, Dingkun Yin², Junqi Li³, Xianwei Zhang², Wenhai Wang², Xing Fang⁴, Honghong Shi², Qi Wang⁵

Affiliations

¹ Key Laboratory of Urban Stormwater System and Water Environment, Ministry of Education, Beijing University of Civil Engineering and Architecture, Beijing 100044, China; Beijing Advanced Innovation Center of Urban Design for Future Cities, Beijing 100044, China.
² Key Laboratory of Urban Stormwater System and Water Environment, Ministry of Education, Beijing University of Civil Engineering and Architecture, Beijing 100044, China.
³ Key Laboratory of Urban Stormwater System and Water Environment, Ministry of Education, Beijing University of Civil Engineering and Architecture, Beijing 100044, China; Beijing Advanced Innovation Center of Urban Design for Future Cities, Beijing 100044, China. Electronic address: lijunqi@bucea.edu.cn.
⁴ Department of Civil Engineering, Auburn University, Auburn, AL 36849-5337, USA.
⁵ China Urban Construction Design Research Institute CO.LTD., Beijing 100120, China.

PMID: 31212159
DOI: 10.1016/j.scitotenv.2019.06.100

Abstract

Green roof is an important measure in "Sponge Cities" to reduce the runoff and improve the runoff quality. The runoff quantity and quality control capacity of five types of extensive green roofs (EGRs) were analyzed in Beijing for 51 nature rainfall events and 6 simulated events from July 2017 to October 2018. Different module scales (sizes) and substrate depths were examined to study their correlation to runoff retention, peak flow reduction, pollutant event mean concentration (EMC) and load reduction performance of EGRs. In general, both the single-field rainfall events and the long-term monitoring showed that as the module scale and substrate thickness increased, the retention capacity of the EGRs increased. As the module scale increased, the peak flow reduction rate (P_frr) of the EGR modules increased, while the thickness of the substrate appeared to have less of an effect on P_frr. When water quality effect was considered, compared with module scale, the substrate thickness had a more obvious effect on the average EMC of different pollutants. As the substrate thickness increased, the EMC of pollutants decreased. Under six simulated design rainfalls, EMC reduction rate of suspended solid (SS) of all types of EGRs ranged from 64.3%-73.1% while no reduction was found in the EMC of chemical oxygen demand (COD). The EMC trends of ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), total nitrogen (TN) and total phosphorus (TP) were almost the same, and their EMCs decreased with increasing total rainfall depth. When the pollutant load was considered, the EGRs in this study were a sink of NH₄⁺-N, NO₃^--N, TN, and TP but a source of COD.

Keywords: Event mean concentration; Extensive green roof; Peak flow reduction; Performance assessment; Pollutant load; Runoff retention.