This paper describes the Santa Susana Field Laboratory and historical site activities, agency-approved interim contaminated soil and material removal, and stormwater management and resulting runoff quality that occurred before the California Department of Toxic Substances Control final clean-up guidance becomes available. This is a unique case study with stormwater samples collected during every runoff event and analyzed for a very broad analytical suite over a period of about twenty-five years at regulated stormwater outfalls, and less frequently at many additional locations within the site, combined with an independent surface water expert panel to support constructive discharger-regulator-public communication and science-based decision making. The use of a variety of allowed interim contaminated soil and material removal actions, in addition to active stormwater treatment, plus distributed passive stormwater controls, were complemented with pollutant source investigations and a statistical spatial screening approach to prioritize critical drainage areas for stormwater treatment. Public involvement included participation in discharge permit hearings, reviews of regulatory agency planned clean-up goals, and attendance at informational meetings, in addition to other activities. This paper is part one of a two-part set. The second paper describes the significant improvements in stormwater quality from the site as these controls have been implemented.
Soil and Water Assessment Tool (SWAT) and SWAT-CUP are semi-distributed, process-oriented models that accurately replicate the hydrological cycle in large and complex watersheds and calibrate the results. The objective of this study is to assess the effectiveness of the SWAT model and SWAT-CUP software for hydrological analysis, evaluate the uncertainty associated with the SWAT model, and analyse runoff. This model delineates the basin into five sub-basins and 200 hydrological response units. The model calibration and validation were performed with the SUFI-2 algorithm for the periods 2012 to 2017 and 2018 to 2020 respectively, incorporating a two-year warm-up phase. The sensitivity analysis indicates that, ESCO, ALPHA_BF, SOL_BD, SFTMP, CN2, and SOL_AWC are the six parameters affecting the hydrological process. This aspect is essential in assessing output runoff. Among these characteristics, SCS-CN and ALPHA_BF were identified as the most sensitive variables. The calibration results from 2012 to 2017 provide exceptional outcomes, with R2, PBIAS and NS values of 0.94, 0.89, 14.9 and 0.93, respectively. The validation phase from 2018 to 2020 demonstrates commendable results for the same model, producing values of 0.92, 0.86, 19.4 and 0.91, respectively. Twelve parameters were established during calibration, which are essential for runoff modeling in the designated region. A thorough comprehension of hydrological processes and the identification of pertinent parameters are crucial for developing a simulation model. SWAT and SWAT-CUP were chosen over alternative models primarily due to their superior capability in uncertainty assessment, which enhances the reliability of hydrological simulations and informs future decision-making in the selected watersheds.
Flow hydraulics and sediment transport influence the overall stability and sustainability of rivers. This work reports the flow hydraulics and water quality parameters of Damercherla and Wadapally, the two gauging stations on the Musi River, Hyderabad, India. The trend analysis of the flow rate of these two gauging stations was carried out using the Mann-Kendall test (MKT) and a revised innovative trend analysis (RITA) by considering parameters such as flow rate, total alkalinity, total hardness, electrical conductivity, chlorine, potassium, sulphate, and pH for the period of 1987–2018. Data was segregated to develop a monthly time series for each parameter. Apart from conductivity and hardness, the average value of all other water quality parameters at these two gauging sites were within the permissible limit of the Bureau of Indian Standards (BIS). The average conductivity value was 882 and 560 µS cm-1, respectively, at the Damercherla and Wadapally gauging stations. The hardness of water at Damercherla and Wadapally was noted to be 239 and 156 mg L-1, respectively, which was greater than the permissible limit of BIS, whereas the average value of alkalinity at Damercherla and Wadapally was 193 and 128 mg L-1, respectively. RITA shows an insignificant discharge trend at Damercherla and a significant discharge trend at Wadapally. Similar trend results were observed for the MKT, too. The rate of decline of discharge is around 33 m3/s at Wadapally during the month of August. The changes observed in discharge at the studied sites on the Musi River may be due to unplanned urbanization and climate change, apart from other contributing factors.
This study investigates the hydrodynamics and sediment transport processes around an isolated submerged non-uniform flexible vegetation (FV) element in an open-channel flow using FLOW-3D HYDRO. The observed reconfigured FV shape is represented using a hybrid solid–porous configuration with a height-varying frontal area and porosity. Numerical simulations incorporate the RNG k–ε turbulence model, the saturated Forchheimer porous-media formulation, and Nielsen’s bedload transport formulation, and are validated against laboratory measurements of velocity profiles and bed elevation changes. Results show that FV induces a distinct three-layer flow structure, with a velocity deficit within the canopy and an accelerated shear layer at the canopy–water interface. Flow vectors reveal wake formation and coherent vortices that promote sediment mobilization, while turbulent kinetic energy (TKE) peaks above the canopy due to shear-layer instabilities. A C-shaped scour hole develops at the FV base, followed by downstream deposition, consistent with experimental observations. Although computational fluid dynamics (CFD) slightly underpredicts the maximum scour and deposition magnitudes, it effectively reproduces the centerline bed-elevation trends (R2 = 0.92) and key morphodynamic patterns with satisfactory agreement. The proposed robust and computationally efficient CFD framework demonstrates the capability of reproducing complex flow–vegetation–sediment interactions in vegetated channel systems and is applicable to river restoration, sediment management, and ecohydraulic design.
Sewer infrastructure is essential to urban functionality but vulnerable to blockages that compromise hydraulic performance and increase maintenance costs. Traditional sewer asset management focuses on structural deterioration, neglecting operational problems such as wipe buildup, a growing source of blockage due to poor disintegration. This research develops a novel algorithm that simulates the formation, growth, and effect of wipe-caused blockages, enhancing urban drainage models by accounting for their hydraulic implications. Capacity loss in sewers due to wipe accumulation was quantified and shown to increase with greater population densities. Results showed the need to adopt structural and operational factors in sewer management. By addressing wipe-caused blockages, this research gives insights into the deterioration of sewer performance that requires better mitigation measures. An improved blockage modeling strategy can be used to enhance asset management, maintain sewer functionality, and provide sustainable urban drainage systems.
