Key Takeaways & Executive Findings
- •• • Under a 5-year return period storm, 47 manholes overflowed and 31.29% of stormwater pipes operated at full capacity, identifying 12 waterlogging-prone points, of which 8 were due to insufficient pipe capacity and 5 due to river backflow. • • Enlarging pipe diameters reduced overflowing manholes by 32 (from 47 to 15) and full-flow pipe length by 20%, significantly decreasing surface ponding area. • • Implementing LID measures reduced overflowing manholes by only 4 and full-flow pipe length by 1.5%, but decreased maximum flooding depth by nearly 1 m, indicating its role in reducing runoff and easing drainage burden. • • River backflow, a critical factor in coastal waterlogging, was observed at 5 of 12 waterlogging points, emphasizing the need to incorporate tidal and storm surge effects in drainage system design.
Abstract
Urban waterlogging, exacerbated by climate change and rapid urbanization, poses increasing risks, particularly in coastal low-lying areas with dense river networks. This study simulated waterlogging in the Shajing River drainage area of the Maozhou River basin, Shenzhen, using the SOBEK hydrodynamic model. Under a 5-year return period rainfall, 47 manholes overflowed and 31.29% of stormwater pipes operated at full capacity. Twelve waterlogging-prone points were identified: eight due to insufficient drainage capacity and five due to river backflow from low elevation. Two optimization schemes were compared: enlarging pipe diameters and implementing Low Impact Development (LID) measures. Pipe enlargement reduced overflowing manholes by 32 and full-flow pipe length by 20%, effectively decreasing surface ponding. LID measures reduced overflowing manholes by only 4 and full-flow pipe length by 1.5%, but decreased maximum flooding depth by nearly 1 m, alleviating drainage system burden. The study highlights the complex causes of coastal urban waterlogging, especially river backflow under tidal influence, and recommends considering sea-level rise and storm surge in drainage design. The findings provide valuable references for attributing waterlogging causes and planning drainage network upgrades in coastal cities.
1. Introduction
Coastal urban waterlogging is a growing threat as climate change intensifies extreme rainfall and urbanization expands impervious surfaces. Unlike inland cities, coastal areas face compound flooding from river discharge, storm surges, and tides, which can obstruct drainage and amplify flood impacts. Traditional drainage systems, designed for historical rainfall patterns, are increasingly inadequate, leading to frequent inundation in low-lying districts. Existing optimization approaches often focus solely on pipe capacity expansion, neglecting the complex interactions with coastal hydrology, such as backwater effects from high river stages.
This study addresses this bottleneck by employing the SOBEK hydrodynamic model to simulate waterlogging in a representative coastal catchment in Shenzhen. The model integrates rainfall, pipe network, and river stage dynamics, enabling attribution of waterlogging to either insufficient pipe capacity or river backflow. By comparing pipe enlargement and LID measures, the research provides a quantitative framework for optimizing drainage systems in coastal settings, explicitly considering the role of tidal and storm surge influences. This approach offers a more robust basis for engineering decisions than conventional methods that ignore coastal-specific failure mechanisms.
Loading authentic research manuscript (Pages 1–5)...
YU Ziwei, LYU Jiajie, TIAN Zhan, YE Qinghua, WANG Yanlong, LIU Qiaodan, TANG Yingdong (2026). Coastal Urban Waterlogging Simulation and Drainage System Optimization: A Case Study of the Shajing River Drainage Area in Shenzhen. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202408057
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What are the primary causes of waterlogging in the Shajing River drainage area, and how were they quantified?
Waterlogging was attributed to two main causes: insufficient pipe drainage capacity (8 of 12 points) and river backflow due to low elevation (5 of 12 points). Quantification was based on SOBEK model simulations under a 5-year return period rainfall, which showed 47 manholes overflowing and 31.29% of pipes at full capacity. The model explicitly simulated river stage interactions, identifying backflow-prone locations.
How does the performance of pipe diameter enlargement compare with LID measures in reducing waterlogging risk?
Pipe enlargement was more effective in reducing manhole overflows (32 fewer) and full-flow pipe length (20% reduction), directly increasing drainage capacity. LID measures reduced overflows by only 4 manholes and full-flow pipe length by 1.5%, but decreased maximum flooding depth by nearly 1 m, indicating that LID reduces surface runoff and eases system burden without rapidly draining water. The choice depends on whether the goal is to eliminate overflows or mitigate flood depth.
What role does river backflow play in coastal waterlogging, and how should drainage design account for it?
River backflow was responsible for 5 of 12 waterlogging points, occurring when high river stages (due to tides or storm surges) prevent stormwater discharge. This is a critical factor often overlooked in inland designs. The study recommends incorporating sea-level rise and storm surge projections into pipe design, possibly using flap gates or pumps to prevent backflow, and considering the dynamic interaction between sewer and river systems.
What are the limitations of the SOBEK model in simulating coastal urban waterlogging, and how were they addressed?
The SOBEK model requires high-resolution input data (pipe networks, topography, rainfall) and may not fully capture localized effects like debris blockage or transient flow. In this study, the model was calibrated against observed waterlogging points, achieving good performance. However, the model assumes steady-state conditions for some parameters, which may underestimate rapid changes during extreme events. Future work could integrate real-time data and ensemble simulations to improve accuracy.
How transferable are these findings to other coastal cities with different drainage and tidal characteristics?
The methodology is transferable, but specific results depend on local conditions. The study provides a framework for attributing waterlogging to pipe capacity vs. backflow, which can be applied elsewhere. However, the relative importance of backflow will vary with tidal range, river slope, and pipe network design. Cities with microtidal ranges may see less backflow, while those with high tidal ranges or low-lying topography should prioritize backflow mitigation. The quantitative thresholds (e.g., 31.29% full-flow) are site-specific and require recalibration.
Related Chinese Research & Cross-Citations
Analysis of National and Local Policies for Medical Waste Treatment and Disposal in China
The escalating generation of medical waste, driven by healthcare expansion and frequent medical activities, poses significant environmental and public health risks. Under the framework of ecological civilization, China is developing a comprehensive policy system for medical waste treatment and disposal, yet the current framework remains nascent and exhibits inconsistencies between national and local policies. This study systematically analyzes the status of national and local policies from 2003 to 2024, collecting 413 policy documents (166 from national ministries and 247 from provincial governments). The analysis examines temporal evolution, regional distribution, and policy focus, alongside the influence of medical waste output, treatment technologies, facility infrastructure, and major epidemic responses. Findings reveal distinct policy phases: initial self-disposal, exploratory management, foundational system building, and rapid development. Regional disparities are pronounced, with eastern coastal areas showing more advanced policies due to greater technical and financial resources. The surge in medical waste, particularly during the COVID-19 pandemic, underscores the need for enhanced regulatory guidance. Non-incineration technologies are gaining traction for their environmental and cost benefits, and facility coverage has improved but remains uneven. The study proposes five policy principles to foster technological innovation and industrial upgrading, ensuring safe medical waste management and environmental protection.
Kinetic Analysis and Simulation of Pollutant Removal in Sewage Networks
This study investigates pollutant removal characteristics and kinetic behaviors in sewage networks, and analyzes their impact on the carbon-to-nitrogen ratio (C/N, as COD/TN) of influent to wastewater treatment plants. Source water quality sampling at drainage outlets revealed spatial and temporal variations in C/N, with domestic sewage exhibiting higher C/N than industrial sewage, and diurnal peaks reaching 6.92 versus 4.71 during off-peak hours. Using a pilot-scale adjustable sewage network system in Kunshan, experiments were conducted under high (0.491 m·s−1) and low (0.089 m·s−1) flow velocities, monitoring pollutant removal over 144 hours. Pseudo-first-order kinetics were applied to model COD and TN removal. Results showed that COD (including SCOD and PCOD), BOD5, and SS achieved approximately 80% removal within 144 h, with higher removal at low flow velocity. TN, NH3-N, and TP exhibited lower overall removal rates. Kinetic fitting revealed that COD removal rate constants (kCOD) were significantly higher than those for TN (kTN), and both decreased with increasing flow velocity: at low velocity, kCOD=0.0167 h−1 and kTN=0.0029 h−1; at high velocity, kCOD=0.0127 h−1 and kTN=0.0020 h−1. Simulations based on actual source pollutant concentrations indicated that the time for C/N to drop to the denitrification critical value of 4.50 was 12.24 h at high velocity, but shortened to 9.49 h at low velocity. These findings demonstrate that increasing flow velocity effectively retards the decline of C/N. Therefore, regulating network flow velocity to reduce hydraulic retention time is a key strategy for maintaining adequate C/N at the terminal and ensuring denitrification efficiency in wastewater treatment plants.
Preparation of Trimetallic-Carbon Composite Catalysts and Their Application in Catalytic Ozonation of Industrial Wastewater
Advanced oxidation processes (AOPs) are promising for degrading organic pollutants in water treatment. Heterogeneous catalytic ozonation (HCO) has gained attention due to its high oxidation efficiency, strong interference resistance, and low secondary pollution. In this study, a series of trimetallic-carbon composite ozone catalysts were prepared via an organic precursor calcination method using γ-Al2O3 as support. This method enhanced catalytic activity and mechanical strength while overcoming the limitations of carbon materials (low mechanical strength) and metal-based materials (poor mass transfer). The optimized catalyst, CA-FeCoCu, comprising Fe, Co, Cu, carbon, and alumina, exhibited excellent performance in phenol degradation and real industrial wastewater treatment. Characterization revealed that the synergistic effect of trimetals and the introduction of multiple carbon types increased specific surface area and hydroxyl radical (·OH) generation. In a pilot-scale fixed-bed reactor, the CA-FeCoCu/O3 system reduced COD from 120 mg·L−1 to below 40 mg·L−1, with an O3 consumption ratio (O/C) of less than 1, effectively lowering operational costs. This work provides a new strategy for developing efficient and stable heterogeneous O3 catalysts and offers a reference for the practical application of HCO in industrial wastewater treatment.
Differentiated Characteristics of Suspended Particulate Matter and Their Effects on Water Quality in the Middle and East Routes of the South-to-North Water Diversion Project
This study investigates the spatiotemporal differentiation of suspended particulate matter (SPM) characteristics, sources, and their impacts on water quality between the Middle Route (closed artificial channel) and East Route (open natural water system) of the South-to-North Water Diversion Project. Thirty sampling sites (13 on the Middle Route, 17 on the East Route) were established, and samples were collected during dry and wet seasons. Water quality parameters and SPM characteristics were analyzed, including particle size distribution, total suspended solids (TSS), chlorophyll a, and stable carbon and nitrogen isotopes. Results show that the Middle Route maintains good and stable water quality, with SPM dominated by coarse particles (>63 μm, 61.43%–94.68%), total phosphorus (TP) <0.01 mg·L−1, and a significant positive correlation between chlorophyll a and coarse particles (r=0.60), indicating algal aggregation dominates particle formation. In contrast, the East Route exhibits high and fluctuating nitrogen and phosphorus concentrations, with SPM dominated by fine particles (<20 μm, 51.26%–88.61%), TP ranging from 0.03 to 1.11 mg·L−1, and a positive correlation with fine particles, suggesting significant external inputs. Carbon and nitrogen isotope analysis reveals that Middle Route SPM primarily originates from autochthonous algae (contribution >46.75%), while East Route SPM is influenced by both terrestrial C3 plants and algae. The distinct engineering and management approaches of the two routes lead to significant differences in SPM characteristics and sources, thereby affecting water quality dynamics. The Middle Route requires an 'algal reduction and hydrodynamic optimization' strategy to control algal-derived coarse particle deposition, whereas the East Route benefits from 'retention-sedimentation and wetland purification' to reduce external fine particles and pollutant inputs. This research provides theoretical support and practical guidance for differentiated SPM management in long-distance water diversion systems.
Combined Ozone Micro-Nano Bubble Oxidation and Powdered Activated Carbon Adsorption for Removal of Taste and Odor Compounds from Drinking Water
Algal-derived taste and odor compounds (2-methylisoborneol, 2-MIB, and geosmin, GSM) in drinking water sources are poorly removed by conventional treatment. This study systematically evaluated the standalone and combined performance of ozone micro-nano bubbles (O3-MNBs) oxidation and powdered activated carbon (PAC) adsorption for removing 2-MIB, GSM, and algal cells from source water. Results showed that O3-MNBs pre-oxidation achieved >97.5% removal of odorants at 400 ng·L−1 and 67.2% algal cell removal within 30 min. When applied as a deep treatment stage, the degradation rate constant (k) was 10.1%–25.6% higher than in pre-oxidation due to lower background matrix interference. Both pre-oxidation and deep treatment reduced effluent concentrations of 2-MIB and GSM to below 10 ng·L−1, with oxidation kinetics fitting pseudo-first-order models (R²>0.95). PAC adsorption of both compounds followed pseudo-second-order kinetics (R²>0.99), with GSM equilibrium adsorption capacity approximately 20.0% higher than that of 2-MIB. In pure water, adsorption capacity increased by >10.0% compared to raw water. Based on kinetic models, a quantitative prediction method was established for O3-MNBs oxidation and PAC adsorption processes, aiming to achieve efficient odorant removal and cost optimization, providing theoretical support for advanced drinking water purification and smart water plant construction.
Pulsed Electric Field Enhancement of Nitrogen Removal Performance and Microbial Community Structure Response in Anammox Granular Sludge
This study investigated the effects of a ring-shaped pulsed electric field (PEF) (1.5 V, 4 h on-time per cycle) on nitrogen removal performance and microbial community structure of anammox granular sludge (AnGS). Two anaerobic sequencing batch reactors (R1 control, R2 with PEF) were operated under stepwise increasing nitrogen loading rates (NLR). At NLR below 1,155 mg·(L·d)−1, R2 exhibited total nitrogen removal efficiency (TRE) 7.5%–17.0% higher than R1, with biomass, specific anammox activity (SAA), and extracellular polymeric substances (EPS) increased by 5%–7%, 21%–71%, and 54%–77%, respectively. However, at NLR above 1,320 mg·(L·d)−1, the toxic effect of nitrite dominated, and PEF enhancement diminished or even reversed to inhibition. Microbial community analysis revealed that at low-to-moderate NLR, PEF increased the relative abundance of Planctomycetes and key anammox bacteria (Candidatus Brocadia and Candidatus Jettenia), along with enhanced community richness (Chao1) and diversity (Shannon/Simpson indices). At high NLR, PEF decreased microbial richness compared to R1. Principal component analysis and redundancy analysis indicated that PEF was the key factor driving community differences at low-to-moderate NLR, whereas nitrite concentration became the dominant factor at high NLR. This study provides theoretical support for enhancing the resilience and engineering application of anammox processes.