ARTICLE | doi:10.20944/preprints201807.0075.v1
Subject: Engineering, Civil Engineering Keywords: ANCOVA; Blockage; Clogging; Efficient; Green infrastructure; Infiltration bed; Orifice; Perforation; Performance; Philadelphia; Pipe; Stormwater
Online: 4 July 2018 (15:18:14 CEST)
Performance of flow through orifices on a perforated distribution pipe between periods with and without partial clogging (submersion of part of the distribution pipe) was compared. The distribution pipe directly receives runoff and delivers it to an underground infiltration bed. Partial clogging appeared in winter but reduced in summer. Performance was defined as flow rate divided by l_eff (h_(d,mean)^0.5) where h_(d,mean) is the mean pressure head that drives flow and l_eff is the effective pipe length (length of water column with pipe water volume and the pipe cross-sectional area). ANCOVA (ANalysis of COVAriance) was adopted to examine the clogging effects with flow rate plotted against l_eff (h_(d,mean)^0.5) . Partial clogging had a significant effect on pipe performance during periods of low or no rainfall. However, if only data during larger storms was considered, little evidence showed that partial clogging had effects on pipe delivery performance. Partial clogging might be caused by leaves accumulated in the lower section of the pipe in winter, and its effect was insignificant when water level rose in the pipe, utilizing significantly more orifices on the distribution pipe, thus the effect from the clogged portion had negligible impact on system performance. Larger storms might also provide the required flow rate to move the debris block thus exposing the orifices. Partial clogging did not increase the tendency of overflow; therefore, current maintenance schedule was sufficient to keep the distribution pipe at satisfactory performance even though partial clogging can exist.
ARTICLE | doi:10.20944/preprints201710.0108.v1
Subject: Earth Sciences, Environmental Sciences Keywords: Variance Inflation Factor; VIF; multiple regression; Landsat; Austin; Lady Bird Lake; water quality; environmental factor; energy flux; urban runoff
Online: 17 October 2017 (03:38:28 CEST)
A simple approach to enable water-management agencies employing free data to achieve the goal of using a single set of predictive equations for water-quality retrievals with satisfactory accuracy is proposed. Multiple regression-derived equations based on surface reflectance, band ratios, and environmental factors as predictor variables for concentrations of Total Suspended Solids (TSS), Total Nitrogen (TN), and Total Phosphorus (TP) were derived using a hybrid forward-selection method that considers Variance Inflation Factor (VIF) in the forward-selection process. Landsat TM, ETM+, and OLI/TIRS images were jointly utilized with environmental factors, such as wind speed and water surface temperature, to derive the single set of equations. The coefficients of determination of the best-fitting resultant equations varied from 0.62 to 0.79. Among all chosen predictor variables, ratio of reflectance of visible red (Band 3 for Landsat TM and ETM+, or Band 4 for Landsat OLI/TIRS) to visible blue (Band 1 for Landsat TM and ETM+, or Band 2 for Landsat OLI/TIRS) has a strong influence on the predictive power for TSS retrieval. Environmental factors including wind speed, remote sensing-derived water surface temperature, solar altitude, and time difference (in days) between the image acquisition and water sampling were found important in water-quality parameter estimation.
ARTICLE | doi:10.20944/preprints201909.0083.v2
Subject: Engineering, Civil Engineering Keywords: evapotranspiration; green infrastructure; HYDRUS; leaf water potential; low impact development; optimization; overdesign; stomatal conductance; simulated runoff test; static sizing; stormwater control measure; tree trench
Online: 15 January 2020 (07:28:40 CET)
Green infrastructure systems are often overdesigned. This may be a byproduct of static sizing (e.g., accounting for a design storm’s runoff volume but not exfiltration rates) or may be deliberate (e.g., buffering against performance loss through time). Regardless, overdesign may compromise plants’ access to water in systems where soil pits are embedded in infiltration beds. It could raise the storm size required for water to reach soil pits, reducing water availability between storms, which could ultimately induce plant physiological stress. This study investigated the hydrological dynamics and water relations of a tree trench system suspected to have been overbuilt and identified factors contributing to, compounding, and mitigating the risk of plant stress. Results provided strong evidence that the abovementioned processes played out. Water in the infiltration bed reached soil pits only once in three years, with that event occurring during a hydrant release. Moreover, minimal water was retained in the soil pit during the event due to the hydraulic properties of the soil media. Through a growing season, one of the two tree types frequently experienced water stress, while the other did so only rarely. These contrasting responses can likely be attributed to roots either being largely confined to the soil pits or reaching a deeper water source. Implications of these results for green infrastructure design are considered.