Monitoring and Evaluating Rainfall-Runoff Control Effects of a LID
System in the Future Science Park of Beijing
Abstract
The actual rainfall–runoff control effects of a low-impact development
(LID) system comprising multiple facilities within a large-scale area
need to be monitored and examined, including not only the rainfall
volume capture effect but also the rainfall control mode, which is
influenced by the confluence relationship. The confluence relationship
between an impervious surface and LID facilities can be manifest as a
series or parallel system. For individual rainfall events smaller than
the designed rainfall, rainfall control operates in event-capture mode
for a series system and in partial-capture mode for a parallel system.
Although the rainfall volume capture ratios of series and parallel
systems might be equivalent, a series system is more suitable for water
quality improvement and peak flow reduction. This study considered the
Future Science Park of Beijing as a case study site. Monitoring
indicated that the rainfall volume capture effect is acceptable because
the average runoff coefficient is approximately 0.10; however, rainfall
control operates in partial-capture mode. Investigation and analysis
showed that runoff is generated by three mechanisms: impermeable road
surfaces, infiltration excess, and pipe storage-water emission. When
rainfall volume is less than the designed rainfall, the little runoff
that occurs is generated mainly by the impermeable road network. The
rainwater infiltration capacity of permeable facilities might reach 44
mm. In future, to improve rainfall–runoff control effects, impermeable
roads and green belt areas alongside the roads should realize series
confluence.