Influence of <i>In-situ</i> Soil and Groundwater Level on Hydrological Effect of Bioretention

Abstract

Bioretention is an important technology for ecological control of runoff. The purpose of this study was to investigate the coupling effect of in-situ soil and groundwater level on the hydrological performance of bioretention. VADOSE/W was used to simulate the water transport processes during bioretention under a single rainfall event. The effects of four in-situ soil types and two groundwater levels on the surface ponding, underdrain outflow, exfiltration, and runoff regulation effects of bioretention were studied. Under eight geological situations and the rainfall of 0.17 mm/h (6.0 h), the ponding duration and overflow volume of bioretention were 556-649 min and 24.71-39.61 mm/m 2 , respectively; the underdrain outflow peak value and duration were 0.549-0.804 mm/min and 380-730 min, respectively; the exfiltration volume per unit area from the bottom and lateral of bioretention were 106.79-396.10 mm/m 2 and 50.60-147.45 mm/m 2 , respectively; and the runoff reduction rate, runoff peak reduction rate, and runoff delay time of bioretention were 53.46%-96.19%, 18.43%-68.08%, and 288-318 min, respectively. These results suggest that bioretention without an underdrain and with a relatively smaller K s (saturated permeability coefficient) of in-situ soil might result in longer ponding times and larger overflow volumes. With an increase in K s of in-situ soil, the underdrain outflow weakens, the exfiltration volume increases, and the runoff control effects improve. Although the groundwater level has little effect on surface ponding, it can cause a stronger underdrain outflow. The shallower groundwater level leads to a larger exfiltration volume when the K s of in-soil is much smaller than that of the planting layer and leads to a reduced runoff regulation effect for bioretention without an underdrain. Therefore, when locating and designing bioretention systems, the in-situ soil type and groundwater level should be comprehensively considered to ensure that the runoff control target is achieved.

The Carbon Emission Intensity of Rainwater Bioretention Facilities

“…Higher initial PCs can slow this process, and the runoff control effect improves. This is similar to the findings of Pan et al [55]. The life cycle carbon emissions of the BF ranged from −886.6840 kg CO 2 to −676.5319 kg CO 2 under soil PCs of 50 mm/h to 150 mm/h.…”

Assessment of Runoff Control Effect with Improved Stepped Bioretention System (ISBS) under Various Rainwater Conditions

“…This would lead to the gradual decrease of the soil permeability coefficient and finally reach a stable value, so the soil layer is no longer the main factor affecting infiltration, and thus reducing the advantages of ISBS in runoff control [29]. The above experimental phenomena are similar to the research of Pan et al, which shows that with the increase of the saturated permeability coefficient of in-situ soil, the underdrain outflow weakens, the exfiltration volume increases and the runoff control effects improve [30]. By comparing the rainfall data on June 29 and August 8, with the increase of rainfall, the runoff rainwater stored in the aquifer cannot penetrate in time, resulting in a large amount of overflow Compared with OSBS, the runoff rainwater stored in the ISBS aquifer can directly overflow to the top of the filling layer, which can effectively avoid the adverse impact of the permeability coefficient of the soil layer.…”

Evaluating the Effectiveness of Bioretention Cells for Urban Stormwater Management: A Systematic Review

“…More specifically, bioretention acts as a buffer to runoff peak flow by producing ponds on the surface, keeping runoff within the media and slowly releasing it [60]. BRCs may continue to gradually release water downstream through the underdrain for several days after precipitation events [55,60,65]. Concerning the capture, the term "Bioretention Abstraction Volume" (BAV) was developed in [63] to represent the volume captured by BRCs.…”