Overflow Discharge Research Articles

Stepped chute energy dissipation structure downstream of a low-level river crossing for embankment protection

A low-level river crossing is an economic means of providing access for lower-order roads during high-frequency flood events. Conventionally, culverts are employed to enable the flow to traverse the road, albeit with allowance for overtopping. This overtopping flow from the approach roads, however, possesses the potential to cause erosion of the downstream embankment, thereby jeopardising the foundational integrity of the structure. A physical modelling study was undertaken to investigate the hydraulic performance of stepped chutes in terms of flow patterns, air-water flow properties, and energy dissipation. Various types of stepped chutes were investigated, namely horizontal steps with a chute wall, horizontal steps without a chute wall but with riprap placed directly downstream of each chute, step-inclined steps (backward sloping), steps with pooled cascades, and steps with baffle blocks. Notably, chutes with horizontal steps were the most efficient configuration in terms of relative energy dissipation. Furthermore, this research culminated in the formulation of a new regression formula to establish a quantifiable relationship between the required step length and the overflow depth and discharge, thereby offering a valuable tool for design purposes.

Unraveling the synergistic mechanisms of coagulation combined with oxidation for the treatment of sewer overflow: The interaction between iron species and NaClO

During wet weather, sewer overflow pollution can pose a serious threat to surface water. In order to reduce the impact of overflow discharge on receiving waters, ferric chloride (Fe(Ⅲ))/potassium ferrate (Fe(Ⅵ))/polyacrylamide (PAM) coagulation (Fe(Ⅲ)/Fe(Ⅵ)/PAM) combined with sodium hypochlorite (NaClO) oxidation was proposed. Different combinations were constructed, including pre-oxidation coagulation (NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM), pre-coagulation oxidation (Fe(Ⅲ)/Fe(Ⅵ)/PAM-NaClO), and synchronous coagulation oxidation (NaClO+Fe(Ⅲ)/Fe(Ⅵ)/PAM). The combined processes achieved efficient removal of conventional contaminants, and the produced byproducts were controlled, especially in the NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM. The obvious discrepancy in the sulfamethoxazole (SMX) removal was observed in different processes. NaClO affected the distribution of hydrolyzed iron species, and the proportion of active iron in the NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM significantly increased. More complexation sites were generated in the NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM, which can complex with the coagulant and then effectively transfer to the flocs. The composition of the flocs further confirmed the differences in coagulation characteristics. The generated·OH played a crucial role in SMX removal in the NaClO+Fe(Ⅲ)/Fe(Ⅵ)/PAM, and ClO·was responsible for partial removal of ammonia nitrogen (NH4+-N). The contribution of high-valent iron species was confirmed, and the introduction of NaClO promoted the generation of iron species. This study may provide an ideal for overflow treatment to improve the urban water environment.

Plastic Analysis with a Plasmonic Nano-Gold Sensor Coated with Plastic-Binding Peptides.

Contamination with plastics of small dimensions (<1 µm) represents a health concern for many terrestrial and aquatic organisms. This study examined the use of plastic-binding peptides as a coating probe to detect various types of plastic using a plasmon nano-gold sensor. Plastic-binding peptides were selected for polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS) based on the reported literature. Using nAu with each of these peptides to test the target plastics revealed high signal, at 525/630 nm, suggesting that the target plastic limited HCl-induced nAu aggregation. Testing with other plastics revealed some lack of specificity but the signal was always lower than that of the target plastic. This suggests that these peptides, although reacting mainly with their target plastic, show partial reactivity with the other target plastics. By using a multiple regression model, the relative levels of a given plastic could be corrected by the presence of other plastics. This approach was tested in freshwater mussels caged for 3 months at sites suspected to release plastic materials: in rainfall overflow discharges, downstream a largely populated city, and in a municipal effluent dispersion plume. The data revealed that the digestive glands of the mussels contained higher levels of PP, PE, and PET plastic particles at the rainfall overflow and downstream city sites compared to the treated municipal effluent site. This corroborated earlier findings that wastewater treatment could remove nanoparticles, at least in part. A quick and inexpensive screening test for plastic nanoparticles in biological samples with plasmonic nAu-peptides is proposed.

Significant UK Environmental Law Cases 2023–24

Abstract This case law overview comments on significant UK environmental law cases for the period 1 April 2023–31 March 2024 (with one exception where a High Court decision within that period was overturned on appeal just after it). It begins with an overarching introduction, which draws some general themes from our selection of cases, focussing on the breadth of environmental law and issues of public concern in public and private law disputes. It then addresses 12 significant cases concerning the accrual of causes of action in private nuisance, whether there is power to vary abatement notices in respect of statutory nuisances, climate change, habitats, flooding, cumulative environmental impact assessment, river basin management plans, storm overflow discharge reduction plans, Regulators’ Codes, and public rights on Dartmoor Commons. It ends with some final thoughts on this year’s cases and the year ahead.

Flood Mapping Using HEC-RAS and HEC-HMS: A Case Study of Upper Citarum River at Dayeuhkolot District, Bandung Regency, West Java

Dayeuhkolot district is an area within Citarum River watershed that often experiences flood during the rainy season due to overflow discharge. This research identifies the flood area by using hydrodynamic modeling in Dayeuhkolot district. The model utilized satellite rainfall data. The hydrodynamic modeling of HEC-RAS 5.0.5 and HEC-HMS simulate the flow regimes and the hydrological characteristics in the study area, respectively. The results reveal that the increase in water level in two river tributaries within Citarum River watershed had caused the flooding at Dayeuhkolot district. Furthermore, the percentage of flood areas with low, medium, and high flood risk is 34.7%, 34.5%, and 30.8%, respectively. The flood map developed in this study could support the establishment of a strategy for managing the floodplain area and flood-affected areas.

Water availability of Akelamo River, Obi Island, South Halmahera

The nickel mining industry’s activities are not spared from the high quantity of water demand, such as those of Harita Nickel Indonesia, a company located in Obi Island, South Halmahera. As one of the largest nickel mining companies that uphold environmental conservation, Harita Nickel Indonesia conducted this study to identify and analyze water availability to ensure the company’s and local residents’ water needs. One of the water resources in this study is Akelamo River, which has a 254.99 Km2 catchment area (covering the catchment area of Karo Lake upstream). Referring to SNI 6738:2015, water availability can be indicated by the amount of dependable flow based on an 80% probability of occurrence. This calculation is carried out using F.J. Mock method that heavily relies on six (6) defining variables: Reflection coefficient (r), Exposed surface (m;%), Soil moisture capacity (ISMC), Infiltration coefficient (if), Flow recession constant (k), and Percentage factor (PF). Based on the method and conditions of this location, it is calculated that the dependable flow Q80 of the Akelamo River is 6.2 m3/sec. It should be noted that this figure only represents overflow discharge and does not include the amount of water currently stored in the water body. This availability study can be continued with a water balance analysis according to the planned water demand or even as a consideration in hydrological infrastructure planning such as dams.

Improving the interpretability of deep reinforcement learning in urban drainage system operation

Deep reinforcement learning (DRL) has been increasingly used as an adaptive and efficient solution for real-time control (RTC) of the urban drainage system (UDS). Despite the promising potential of DRL, it is a black-box model whose control logic and control consequences are difficult to be understood and evaluated. This leads to issues of interpretability and poses risks in practical applications. This study develops an evaluation framework to analyze and improve the interpretability of DRL-based UDS operation. The framework includes three analysis methods: Sobol sensitivity analysis, tree-based surrogate modelling, and conditional probability analysis. It is validated using two different DRL approaches, i.e., deep Q-learning network (DQN) and proximal policy optimization (PPO), which are trained to reduce combined sewer overflow (CSO) discharges and flooding in a real-world UDS. According to the results, the two DRLs have been shown to perform better than a rule-based control system that is currently being used. Sobol sensitivity analysis indicates that DQN is particularly sensitive to the flow of links and rainfall, while PPO is sensitive to all the states. Tree-based surrogate models effectively reveal the control logic behind the DRLs and indicate that PPO is more comprehensible but DQN is more forward-looking. Conditional probability analysis demonstrates the potential control consequences of the DRLs and identifies three situations where the DRLs are ineffective: a) the storage of UDS is fully utilized; b) peak flows have already passed through actuators; c) a substantial amount of water enters one location simultaneously. The proposed evaluation framework enhances the interpretability of DRL in UDS operations, fostering trust and confidence from operators, stakeholders, and regulators.

Discharge coefficients formulae of grate inlets of complicated conditions for urban floods simulation and urban drainage systems design

With the acceleration of climate change and urbanization, all over the world is widely facing serious urban flooding problems. Grate inlets are key elements for the discharge exchange of surface flows and underground sewer flows in urban floods, so the accurate calculation of the overflow discharges of the grate inlets is related to the accurate simulation of the urban flood evolution process, which also plays an important role in the design of sustainable urban drainage systems. This study investigated the discharge coefficients of six types of grate inlets under different approaching discharges, transverse and longitudinal road slopes through 285 indoor 1:1 tests, mainly focusing on the supercritical flow conditions with less attention before. The experimental results show that: (1) With all other parameters being equal, as the interception discharge Q increases, the discharge coefficient increases. When the approaching Froude number increases, the discharge coefficient also decreases. The performance of parallel grate inlets in terms of discharge coefficients is not significantly different from that of vertical grate inlets. (2) Using Buckingham’s theorem of dimensional analysis, 12 groups of accurate grate inlets discharge coefficient calculation formulae were creatively proposed. The average relative errors of the 12 groups of formulae are 0.37% ∼ 5.41%, indicating that the calculated values of the formulae and the measured values are in good agreement. (3) The discharge coefficients of grate inlets were found to show a strong dependence on the Froude number of the approaching discharge, being in agreement with previous study result. But the relative error of individual data in this method is large, so the use of equations with more influencing parameters is recommended. A novel and effective method was also proposed to calculate the interception discharge of the grate inlets by iteration. This study can provide important references for the design and selection of grate inlets for urban drainage systems and also provide support for accurate simulation of urban floods.

Global resilience analysis of combined sewer systems under continuous hydrologic simulation

Managing and reducing combined sewer overflow (CSO) discharges is crucial for enhancing the resilience of combined sewer systems (CSS). However, the absence of a standardised resilience analysis approach poses challenges in developing effective discharge reduction strategies. To address this, our study presents a top-down method that expands the existing Global Resilience Analysis to quantify resilience performance in CSS. This approach establishes a link between threats (e.g., rainfall) and impacts (e.g., CSOs) through continuous and long-term simulation, accommodating various rainfall patterns, including extreme events. We assess CSO discharge impacts from a resilience perspective by introducing eight new metrics. We conducted a case study in Fehraltorf, Switzerland, analysing the performance of three green infrastructure (GI) types (bioretention cells, green roofs, and permeable pavements) over 38 years. The results demonstrated that GI enhanced all resilience indices, with variations observed in individual CSO performance metrics and their system locations. Notably, in Fehraltorf, green roofs emerged as the most effective GI type for improving resilience, while the downstream outfall displayed the highest resilience enhancement. Overall, our proposed method enables a shift from event-based to continuous simulation analysis, providing a standardised approach for resilience assessment. This approach informs the development of strategies for CSO discharge reduction and the enhancement of CSS resilience.

Denitrification Potential of Surface Soils of Constructed Wetlands in Newtown Creek, an Urban Superfund Site.

Denitrification, the anaerobic microbial conversion of nitrate (NO3 - ), a common water pollutant, to nitrogen (N) gases, is often high in the soil of natural wetlands. In areas where natural wetlands have been degraded or destroyed, constructed and restored wetlands have been used to restore ecosystem services like denitrification. Thus, denitrification in restored and constructed wetlands could play an important role in treating anthropogenic N sources such as combined sewer overflow (CSO) discharges which can be high in NO3 - . In this study, we measured denitrification potential using an anaerobic slurry assay and made a suite of ancillary measurements (soil moisture content, microbial biomass carbon (C) and N content, potential net N mineralization and nitrification, soil inorganic N pools and soil respiration) in four constructed salt marsh wetlands, and a series of wetland habitat basins in Newtown Creek, NY, an urban superfund site. Samples were also taken from natural salt marshes located at Paerdegat Basin, Jamaica Bay, NY. Our results show that constructed Spartina alterniflora marshes in ultra-urban Newtown Creek support denitrification potential equivalent to rates of natural marshes in Jamaica Bay and reference marshes in other urban estuaries. There were significant positive correlations between microbial biomass C and N content and organic matter content and denitrification potential. Results suggest that constructed wetlandscan support wetland vegetation, soils, and microbial life and contribute to N removal under ultra-urban conditions. This article is protected by copyright. All rights reserved.

Microplastics discharged from urban drainage system: Prominent contribution of sewer overflow pollution

Urban drainage system is an important channel for terrigenous microplastics (<5 mm in size) to migrate to urban water bodies, especially the input load caused by overflow pollution in wet weather. Investigating how they transport and discharge is essential to better understand the occurrence and variability of microplastics in different water ecosystems. This study evaluated the abundance and distribution characteristics of microplastics in the drainage systems of typical coastal cities in China. The impacts of meteorological conditions and land use were explored. In particular, the prominent contribution of drainage sewer overflow pollution during storm events were investigated. The results showed that the microplastics abundance in daily sewage discharge from different drainage plots ranged between 13.6 and 30.8 items/L, with fibers as the dominant type of microplastics. Sewer overflow discharge can greatly aggravate microplastic abundance to 83.1 ± 40.2 items/L. Road runoff and sewer sediment scouring were the main pollution sources. Systematic estimates based on detailed data showed that the average microplastics emitted per capita per day in household wastewater was 3461.5 items. A quantitative estimation method was proposed to show that the annual emissions load of microplastics via urban drainage system in this research area was 5.83×1010 items/km2, of which the proportion of emissions in wet weather accounted for about 60%. This research provides the first full-process of assessment and source apportionment of the microplastic distribution characteristics in old drainage system. The occurrence of storm events is an important marker of increased microplastic abundance in urban rivers, with a view to urgent need for interception of surface runoff and purification of sewer overflow pollution.

Hydrodynamics of tidal bore overflow on the spur dike and its influence on the local scour

In estuaries with strong tidal bore, the scour behind the spur dike induced by tidal bore overflow has significant influence on the dike safety. In this study, an experiment study of the local scour induced by tidal bore overflow behind the spur dike was carried out in a physical flume. In addition, the process of the tidal bore overflow on the dike was numerically simulated with the boundary generation method. The stable overflow water depth on the spur dike (hts), unit overflow discharge (qts) and the scour hole characteristics were analyzed based on the experimental and numerical results. It is found that the relative stable overflow water depth (hts/h1) increases with the increase of the Froude number after bore (Fr1) and decreases with the increase of relative dike height (hd/h1). While the relative stable unit overflow discharge (qts/q1) is mainly affected by the relative dike height. Additionally, the results of scour pit behind the spur dike show that the scour depth (s/h1) is directly proportional to the relative current intensity (u1/uc) and the dike height (hd/h1), but inversely proportional to the water depth before bore (h0/h1). An empirical equation for predicting relative maximum scour depth is obtained by fitting the experimental results and the field measured data, and the prediction accuracy is within 30%. The conclusions of this paper can provide technical support for the engineering design and operation evaluation of spur dikes in estuaries with the strong tidal bore.

Performance of Storm Overflows Impacting on Shellfish Waters in England

Storm overflow (SO) discharges to shellfish growing waters are a concern for shellfish growers and may pose a health risk to consumers. We investigated the performance of permitted SOs with a shellfish water spill monitoring requirement against the design criterion of 10 spills per year (averaged over 10 years) used in England. Performance against this criterion over the period 2019–2021 differed between the five water companies whose data was analysed. Across all companies, over half of SOs spilled more frequently than this criterion (percentage greater than 10 spills: 52%, 55% and 57% for 2019, 2020 and 2021, respectively). The number of SOs with the monitoring requirement also differed considerably between the water companies and consequently some companies deal with a significantly higher ‘burden’ than others. The number of SOs spilling more than 100 times in a year also differed between water companies, from 0% (Wessex Water) to 16% (United Utilities). Discharges from SOs can lead to short-term reductions in water quality that may be missed by routine monitoring programmes using faecal indicator bacteria such as E. coli. Such discharges can lead to a higher incidence of norovirus in shellfish and thus potential illness in consumers. We conclude that site-specific impact assessments, supported by spill event-based monitoring, are required given the increased demands on sewerage networks from urban growth and climate change and the need to improve shellfish production area classifications.

Overflow Tests on Grass-Covered Embankments at the Living Lab Hedwige-Prosperpolder: An Overview

In regions with a temperate climate, a well-maintained grass sod on a clay layer is considered a reliable protection for dams and dikes. In the Living Lab Hedwige-Prosperpolder, on the left bank of the Scheldt river straddling the border between Belgium and the Netherlands, a series of 27 overflow tests with a purpose-built overflow generator has been executed to determine the strength of the protective layer against erosion at various conditions. The goal of this paper is to inform on the executed test program and the initial results. From the results, it was concluded that in general, a high-quality grass cover on the landside dike slope can withstand high overflow discharges well for 12 to 30 h, without severe erosion damage. Anomalies, such as the presence of animal burrows, reed vegetation, and already present deformations can strongly reduce the resistance of the cover layer and may lead to failure within a couple of hours.

Application of Head Loss Coefficient for Surcharge Straight Path Manhole to Improve the Accuracy of Urban Inundation Analysis

Currently, adopted runoff analysis models focus on the characteristic factors of watersheds and neglect the analysis of the flow in conduits. Additionally, the usually employed XP-SWMM modeling package generally underestimates the flood area because it considers manholes as nodes and does not consider local head losses according to the shape and size of the nodes. Therefore, it is a necessity to consider the loss coefficient in surcharge manholes to improve inundation and runoff analysis methods. This study aims at improving the accuracy of discharge analysis before analyzing the storage and runoff reduction effects of storage facilities. Hydraulic experiments were conducted according to the changes in discharge and manhole shapes. We show that the flood area increases as the overflow discharge at manhole increases due to the application of the head loss coefficient. We demonstrate a concordance rate ≥95% between results and observed flood area when accurate input data (from the parameters of the target watershed) and the head loss coefficient (from hydraulic experiments) are applied. Therefore, we demonstrate that the result of our 2D inundation analysis, considering the head loss coefficient in surcharge manhole, can be used as basic data for accurately identifying urban flood risk areas.

Penanganan Banjir Sub-DAS Posindo Kota Balikpapan dengan Optimalisasi Penyediaan Infrastruktur Hijau

The Posindo sub-basin, emptying into the Ampal river, is experiencing floods, yet the city government has regularly normalized and cleaned the river. Therefore, this problem cannot be handled conventionally and generically. The research was conducted to formulate optimal flood management scenarios through a green infrastructure approach as an alternative for sustainable flood management. Two analytical methods were used to overcome the research question: the Gumbel Type I distribution to calculate rainfall return periods and HEC-HMS and HEC-RAS modeling software to simulate hydrological and hydraulic conditions. Result analysis showed an overflow discharge above the embankment along the Posindo sub-basin secondary channel by 0.38 – 1.64 m3/s. Alternative’s simulation shows that providing green open space (GOS) is crucial for maintaining water balance in the study area. The combined management scenario by maintaining a minimum GOS of 10%, storage ponds establishment, and increasing the drainage capacity adequate to reduce the overflow height.

Modeling Coastal Freak Wave Occurrence

Fishermen frequently suffer accidents and may even drown when they are swept into the sea by coastal freak waves near the shore of northeastern Taiwan. To accurately predict the deformation of free surfaces when waves violently strike coastal structures, the smoothed particle hydrodynamics (SPH) model with a nonlinear and mesh-free numerical approach was adopted in this study. Eight cases based on an actual coastal freak wave accident were simulated. The results show that the maximum splash height of the coastal freak wave in the breakwater was dependent not only on the incident wave but also on the existence of armor blocks. The armor block installation reduces the overflow discharge but enhances the horizontal throw speed of the coastal freak wave by more than five times.

Erosion Resistance Performance of Surface-Reinforced Levees Using Novel Biopolymers Investigated via Real-Scale Overtopping Experiments

This study evaluates a novel biopolymer-based material reinforcement method. A real-scale experiment minimizing flood disasters and economic losses incurred by the collapse of river levees due to overtopping was conducted. At the Andong River Experiment Center, lateral overflow was reproduced to induce levee collapse using sand, reinforced novel materials, and vegetation levees represented as cases 1, 2, and 3, respectively. The flow in the upstream and downstream areas was measured, and fluctuations in the lateral overflow discharge were calculated using an acoustic Doppler current profiler. To quantitatively verify the performance of this method, the collapse delay effect based on the surface loss rate of the levee slope was analyzed using image pixel analysis and three-dimensional point cloud modeling. Comparing the collapse delay effect of the new-material levee with that of the non-reinforced levees, we found a time delay of approximately 2.7–7 times from the occurrence of overtopping via the lateral flow to the end of the test. These results indicate that we can secure time for emergency repairs and operations by reinforcing the levee surface using the material proposed in this study. These research findings are expected to provide the basis for the proper design and construction of river levees.

Effects of surface roughness on overflow discharge of embankment weirs

Effects of surface roughness on overflow discharge of embankment weirs

Mechanistic modeling and simulation of grinding iron ore pellet feed in pilot and industrial-scale ball mills

Various approaches have been used over the years to describe quantitatively ball milling, with different levels of success. The present work presents the application and validation of a mechanistic model to describe ball milling of iron ore pellet feed. The approach started by estimating selected parameters describing the ore characteristics by back-calculation from batch grinding tests, followed by validation of the model in batch grinding as well as continuous open-circuit ball milling at a pilot-scale operating at a variety of solids concentrations, both with overflow and grate discharge. An industrial ball mill was then laser scanned and surveyed, including measurements of residence time distribution. Simulations using the discrete element method were then conducted and the model was applied to simulate closed-circuit operation, resulting in good agreement between measured and predicted size distributions and circulating load ratio.