Storm Drainage Research Articles

Nitrogen Biogeochemistry of an Urban Rooftop Farm

Intensive agriculture represents a recent extension of green roof technology. Perceived ecosystem services provided by rooftop farming include stormwater management and the production of affordable and nutritious vegetables for local consumption. However, intensive agriculture can increase nutrient loads to surface water, yet there is little empirical data from full-scale operational rooftop farms. This study reports the N balance and N management efficiency of the Brooklyn Grange Navy Yard Farm, a 0.61-ha farm atop an 11-story building in New York City USA. We monitored atmospheric N deposition, soil N concentration, N output by harvest, N leaching from soil, and drainage N output, in addition to estimating net N mineralization and the N load to sewers during the combined sewer overflows. We found that the annual drainage N output was 1100% of the atmospheric bulk N deposition, and was 540% of the estimated total atmospheric N deposition, which makes the Brooklyn Grange a net N source in the urban environment. Annual N leaching from soil was 97% of fertilizer N input, and the efficiency of N management can be lower than in conventional vegetable production. For the Brooklyn Grange to integrate stormwater management and intensive agriculture, it will be important to use soil with greater water holding capacity within the range of readily available water, and to recycle drainage. This case study shows how the intensification of agriculture on rooftops should be managed for both the yield and quality of crops and to reduce N loss to storm drains, which affects aquatic ecosystems and water quality.

Improving stormwater quality at source using catch basin inserts

Stormwater runoff transports contaminants, including gross pollutants (GPs) accumulated on surfaces to nearby receiving water bodies. These may clog storm drainage systems, seal side entry pits and increase dissolved pollutants in receiving water bodies. Best management practices (BMPs) such as oil and grit separators, grassed swales, vegetated filter strips, retention ponds, and catch basin inserts (CBIs) are implemented to reduce stormwater pollutants in urban runoff. However, the information on physicochemical characteristics of the pollutants are still few in literature but important to improve the design of BMPs, considering qualitative aspects, and their operation. CBIs are devices used to remove GPs at source without requiring any extra land use because they are typically mounted within a catch basin (e.g. side entry pit) or existing drain. In this study, improvement of stormwater quality was investigated at two different sites (Subiaco, a residential area and Hillarys Boat Harbour, a commercial-marine-recreational area; Western Australia) where a new CBI made of non-woven polypropylene geotextile was installed in side entry pits to capture GPs at source. Influent and effluent water from the CBIs was collected and analyzed for BOD, COD, TSS and PO4-P with maximum improvements in water quality of 90%, 88%, 88% and 26% respectively. The heavy metals in influent and effluent water were found very low and below the guideline values. Analysis of particle size distribution, specific surface area of solids, SEM images and heavy metal content (Cu, Fe, Ni, Pb, Zn, Cd) in solids showed that the residential area contained more finer particles than the commercial area but that solids in the commercial area contained greater concentrations of heavy metals than those from the residential area. The specific surface area was found to be higher in the residential area and particles were thought to be largely sourced from traffic. However, these characteristics may be monitored for longer term for more CBIs installed in different locations.

Sedimentation Characteristics and Pollutant Content Distribution of Storm Drainage Sediments

To determine the characteristics of precipitation and pollutant content in storm drainage sediments, samples of sediment from building areas (including residential areas), roads, and green spaces in Wuhan were collected and analyzed. The settling velocity results show that particles with high settling velocity weight occupied a larger proportion in the sediment; the settling velocity distribution of sediments in building areas and roads was more stable than that in green spaces; and the proportion of particles with settling velocity over 3.00 cm·s-1 in building areas, roads, and green spaces decreased in turn. The particle size distribution indicated sediment size had a wide variation range, with most particles concentrated in the range 13-628 μm, and that the particle size distribution in sediment from the same land type could differ greatly. Each sample was divided into seven groups according to settling velocity. The contents of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) were tested. The results indicate that pollutant contents in groups containing particles with settling velocity over 3.00 cm·s-1 or below 0.025 cm·s-1 were lower than those in other groups. Most pollutants were concentrated in particles with high settling velocity.The COD concentration declined in green spaces, roads, and building areas, in turn, for most cases. The nitrogen content in the drainage sediment of roads was lower than those in the two other kinds of land, whereas the phosphorus content in the drainage sediment of building areas was higher than those in the two other kinds of land. In the storm drainage sediment, the ratio of COD:TN was between (51-89):1 and that of COD:TP was between (102-186):1.

Identification of sewage markers to indicate sources of contamination: Low cost options for misconnected non-stormwater source tracking in stormwater systems

There has been increasing research focusing on the detection and occurrence of wastewater contamination in urban water systems. To find suitable markers to indicate industrial and domestic sewage flows inappropriately entering storm drains, this study investigated the occurrence and fate of 52 chemical markers through wastewater treatment facilities of manufacturers of agricultural and sideline products, beverage products, and pharmaceutical products, which are also consumed in our daily life. Of the 52 candidate markers, sodium, chloride, potassium, isomalto-oligosaccharide, acesulfame, theanine, glycerol, and clarithromycin were found to be conservative markers, with an average change in concentrations through the wastewater treatment processes of <30%. These markers are useful in identifying industrial and domestic sewage flow contamination in urban sewers. Specially, sodium, chloride, potassium, isomalto-oligosaccharide, acesulfame, and clarithromycin exhibited higher concentrations in blackwater than in greywater, with detected average concentrations of 43.8 mg/L, 189 mg/L, 37.3 mg/L, 123 μg/L, 37.2 μg/L, and 0.99 μg/L in blackwater, respectively. In contrast, theanine and glycerol were observed with higher concentrations in greywater than in blackwater (average 10.1 μg/L and 19.5 μg/L in greywater, respectively). The benchmark concentrations to discriminate between industrial and domestic sewage were also presented. A study in a storm drainage system of downstream Taihu catchment, China demonstrated the usefulness of the markers as low-cost options to trace and quantify misconnected wastewater entries into storm drains, while denoting priority areas for misconnected entries correction.

Re]covering Jeddah’s Wadis – Building the City’s Resilience through Green Infrastructure

Jeddah, Saudi Arabia’s largest coastal city, is positioned between two prominent natural features: the mountain range on its eastern side and the Red Sea on its west. The city faces many challenges central to which is storm water drainage. The natural drainage of the city through its pre-existing wadis, bringing down the rain water from the steep mountain ranges through the low inclining coastal plane and into the sea, has been interrupted in the last few decades by massive road infrastructural projects cutting through the city and interrupting the natural flow. The outcome of these interventions has been excessive flooding calamities, of which the ones in 2009 and 2011 were the most extreme, causing severe damage to infrastructure, property and lives.In light of climate change the intensity of flash floods is expected to increase, placing enormous stress on the city. To control the floods the city has pushed forward heavily engineered solutions, canalizing the rich network of wadis, almost 80 in number, into 4 major concrete channels that discharge the rain water accumulated in the mountains directly into the sea. This solution, which has been prohibitive in cost, has robbed the city of any potential of utilizing the precious supply of rain water. This paper explores the potential of recovering Jeddah’s wadis and creating green corridors across the city. As opposed to engineered solutions which address singular problematics, green infrastructures could provide numerous benefits to the city and the region as a whole.

Tracking the Sources of Antibiotic Resistance Genes in an Urban Stream during Wet Weather using Shotgun Metagenomic Analyses.

Stormwater runoff has been known to cause increases in bacterial loadings in urban streams. However, little is known about its impacts on antibiotic resistance genes (ARGs) in urban watersheds. This study was performed to characterize the ARG composition of various environmental compartments of an urban watershed and to quantify their contributions of microbes and ARGs to an urban stream under wet weather conditions. Shotgun metagenomic results showed that the ARG abundance in wet weather flow was significantly higher than in base flow. Multidrug resistance genes were the most common ARG type across environmental samples. Vancomycin resistance genes were abundant in embankment soil and street sweeping samples. Analyses using SourceTracker estimated storm drain outfall water to be the biggest contributor of microbes (54-57%) and ARGs (82-88%) in the urban stream during wet weather flows. Furthermore, results on street sweepings showed that wash-off from streets was the biggest known contributor of microbes (41-45%) and ARGs (92-96%) in storm drain outfall water. Pantoea and Pseudomonas were associated with the highest numbers of ARGs and were most abundant in stormwater-related samples. Results from this study can advance our knowledge about ARGs in urban streams, an important medium linking environmental ARGs to the general public.

Anthropogenic calling sites boost the sound amplitude of advertisement calls produced by a tropical cricket

Acoustic signals are widely used as sexual displays to attract mates. The choice of display site can strongly influence the male call characteristics and their attractiveness to females. Males can improve the conspicuousness of their signals by increasing sound amplitude and expanding their broadcast area thereby reaching more potential mating partners and influencing female choice. Insects possess a rather limited degree of signal plasticity. To increase the intensity of their calls, insects have been known to manipulate and engineer their display locations. Mole crickets, for example, build burrows that are shaped like horns, designing the burrow such that its resonance closely matches that of their call frequency, thereby boosting sound amplitude. Tree crickets manipulate plant leaves, using them as baffles for optimal sound radiation. In this study, we show for the first time that an insect species can enhance its advertisement calls by using novel, anthropogenic environments as singing sites. During this study, the tropical cricket Anurogryllus muticus was frequently found singing beside the walls of houses, on concrete stairs or in storm drains. These locations significantly increased the sound amplitude of its calls, by an average of 13 and 7 dB SPL, respectively, as measured above and in front of the singing animals compared to the sound amplitude measured in their natural grassland habitat. To evaluate the effect of calling site choice on the male's life span, we conducted a 35-day population survey using the mark and recapture method. Our results revealed that those males that called in grassland habitat without occupying burrows had the shortest minimum life spans.

Wastewater sludge disposal in the claydite construction product

In environmental concern this paper relates to waste management, that is becoming a global challenge. The raw base municipal wastewater sludge (WSS) is submitted by crude types: excess activated sludge (EAS), deposit allocated precipitation at mechanical treatment stage, or also dehydrated mixture of the listed kinds of deposits. Claydite is an effective and rather popular material in the construction industry. The choice of sub-standard clay raw material of an overburden bench of Kalinovo- Dashkovskiy deposit, closely to the city of Serpukhov is provided by a location of opencast on close distance from wastewater treatment plant. As the additive to the specified raw material was chosen small-dispersed WWS with sludge from surface storm drains (SSD), which is poorly investigated. This allowed to specified traditional technology and to improve production light porous claydite, ecologically pure product. Claydite application is possible in production of light concrete on porous aggregate (filler) of the marks up to 600-700 with reduced thermal conductivity up to 0.175 W/m°C. Such a claydite-concrete manages to be received specially working with granulometry of aggregate, utilizing claydite-sand or wastage of dust-ablation. The design for real conditions with productivity 135 thousand M3/year showed the economical substantiation of mentioned claydite production based the identification of power reduction on 25.8% and specific fuel reduction on 25.7 – 38.0% in comparison with traditional values of claydite production.

Precipitation influences pathogenic bacteria and antibiotic resistance gene abundance in storm drain outfalls in coastal sub-tropical waters

Stormwater contamination can threaten the health of aquatic ecosystems and human exposed to runoff via nutrient and pathogen influxes. In this study, the concentrations of 11 bacterial pathogens and 47 antibiotic resistance genes (ARGs) were determined by using high-throughput microfluidic qPCR (MFQPCR) in several storm drain outfalls (SDOs) during dry and wet weather in Tampa Bay, Florida, USA. Data generated in this study were also compared with the levels of fecal indicator bacteria (FIB) and sewage-associated molecular markers (i.e., Bacteroides HF183 and crAssphage markers) in same SDOs collected in a recent study (Ahmed et al., 2018). Concentration of FIB, sewage-associated markers, bacterial pathogens and many ARGs in water samples were relatively high and SDOs may be potentially hotspots for microbial contamination in Tampa Bay. Mean concentrations of culturable E. coli and Enterococcus spp. were tenfold higher in wet compared to dry weather. The majority of microbiological contaminants followed this trend. E. coli eaeA, encoding the virulence factor intimin, was correlated with levels of 20 ARGs, and was more frequently detected in wet weather than dry weather samples. The blaKPC gene associated with carbapenem resistant Enterobacteriaceae and the beta-lactam resistant gene (blaNPS) were only detected in wet weather samples. Frequency of integron genes Intl2 and Intl3 detection increased by 42% in wet weather samples. Culturable E. coli and Enterococcus spp. significantly correlated with 19 of 47 (40%) ARG tested. Sewage-associated markers crAssphage and HF183 significantly correlated (p < 0.05) with the following ARGs: intl1, sul1, tet(M), ampC, mexB, and tet(W). The presence of sewage-associated marker genes along with ARGs associated with sewage suggested that aging sewage infrastructure contributed to contaminant loading in the Bay. Further research should focus on collecting spatial and temporal data on the microbiological contaminants especially viruses in SDOs.

Aquatic exposures of chemical mixtures in urban environments: Approaches to impact assessment.

Urban regions of the world are expanding rapidly, placing additional stress on water resources. Urban water bodies serve many purposes, from washing and sources of drinking water to transport and conduits for storm drainage and effluent discharge. These water bodies receive chemical emissions arising from either single or multiple point sources, diffuse sources which can be continuous, intermittent, or seasonal. Thus, aquatic organisms in these water bodies are exposed to temporally and compositionally variable mixtures. We have delineated source-specific signatures of these mixtures for diffuse urban runoff and urban point source exposure scenarios to support risk assessment and management of these mixtures. The first step in a tiered approach to assessing chemical exposure has been developed based on the event mean concentration concept, with chemical concentrations in runoff defined by volumes of water leaving each surface and the chemical exposure mixture profiles for different urban scenarios. Although generalizations can be made about the chemical composition of urban sources and event mean exposure predictions for initial prioritization, such modeling needs to be complemented with biological monitoring data. It is highly unlikely that the current paradigm of routine regulatory chemical monitoring alone will provide a realistic appraisal of urban aquatic chemical mixture exposures. Future consideration is also needed of the role of nonchemical stressors in such highly modified urban water bodies. Environ Toxicol Chem 2018;37:703-714. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Green roof research towards enhancing urban biodiversity, storm-water retention and air pollution abatement.

Abstract Green roofs provide multiple environmental benefits. These include storm-water retention, water purification, insulation of the building, air quality and carbon sequestration and biodiversity enhancement. Green roofs can be classified as sustainable extensive green roofs (no additional fertilizer, no gardening, no irrigation and shallow growing substrate) or as intensive green roofs (additional fertilizer, gardening, irrigation and deeper growing substrate). In this review, we concentrate on multi-disciplinary benefits of green roofs - i.e. biodiversity enhancement (i.e. reconciliation ecology), storm-water retention and air-pollution abatement as these benefits highly support sustainable buildings. We have found that under conditions of very fine-scale heterogeneity, species diversity (both plants and arthropods) is unlikely to increase, particularly if there is no irrigation. Under large-scale heterogeneity (such as different types of green roofs), the regional diversity can increase. Some plants compete with each other and others can create facilitation. Under conditions of irrigation in the hot, arid conditions of the Middle East, photovoltaic panels may likely produce more electricity and the heterogeneity in solar radiation and moisture can result in greater biodiversity. Rainwater can also be deterred from storm drainage by using gray water irrigation for specific plant assemblages. Green roofs can help mitigate the negative effects of air pollution and CO 2 emissions - in particular, by absorbing pollutants and sequestering carbon dioxide.

Proposing water balance method for water availability estimation in Indonesian regional spatial planning

The water availability (WA) of a region is one of important consideration in both the formulation of spatial plans and the evaluation of the effectiveness of actual land use in providing sustainable water resources. Information on land-water needs vis-a-vis their availability in a region determines the state of the surplus or deficit to inform effective land use utilization. How to calculate water availability have been described in the Guideline in Determining the Carrying Capacity of the Environment in Regional Spatial Planning. However, the method of determining the supply and demand of water on these guidelines is debatable since the determination of WA in this guideline used a rational method. The rational method is developed the basis for storm drain design practice and it is essentially a peak discharge method peak discharge calculation method. This paper review the literature in methods of water availability estimation which is described descriptively, and present arguments to claim that water balance method is a more fundamental and appropriate tool in water availability estimation. A better water availability estimation method would serve to improve the practice in preparing formulations of Regional Spatial Plan (RSP) as well as evaluating land use capacity in providing sustainable water resources.

Simulating Flood Urban Drainage Networks through 1D/2D Model Analysis

Storm drainage design aims to provide safe travel for vehicles and pedestrians as well as to protect properties from damage during storms. The design process m…

Stormwater quality modeling in urbanized areas

Stormwater quality modeling with the use of Stormwater Management Model (SWMM) is presented. The model has been calibrated on the basis of measurements of flow and stormwater quality performed on a real catchment in Łódź, Poland. Calibrated model parameters and the correlations between the quality indexes are given. This will allow application of the model to other urban catchments equipped with storm drainage systems.

Adapting to urban challenges in the Amazon: flood risk and infrastructure deficiencies in Belém, Brazil

Sustainable urban infrastructure transition is perhaps the biggest challenge confronting cities in the global south in a time of climate change. Fast-growing cities are increasingly faced with deficiencies in the provisioning of public infrastructures, such as delivering water and sewage treatment and mitigating the risk of flooding to large segments of the population. Problems such as flooding encapsulate both structural and individual dimensions of adaptation. In this paper, we present a conceptual framework to analyze urban adaptation to increasing flood risk in the capital city of Belem in the Brazilian Amazon. Our analysis focuses on two domains of adaptive capacity to floods: generic capacity (provisioning of basic infrastructure and services) and specific capacity (effective flooding response, proactive strategies for risk reduction). We combined data from census sector and household semi-structured interviews, focus group discussions, observational and archival data, and photo documentation to analyze both capacities in the city of Belem. Our findings indicated deficiency and intra-urban variability of both generic (water supply, sanitation, waste management, and adequate storm drainage) and specific capacities (specific individual and community and political actions for flood mitigation). However, significant inequalities exist across sectors of the population. Poorest urban sectors present higher deficits of generic adaptive capacity related to infrastructure. The expansion of vast areas of informal settlements, lack of basic infrastructure, and failed projects to reduce flood risk also challenge the specific adaptive capacity of households. A perception of corruption associated with public projects and high levels of violence also prevent cooperation and collective action among residents affected by flooding.

Evaluation of the novel crAssphage marker for sewage pollution tracking in storm drain outfalls in Tampa, Florida

CrAssphage are recently-discovered DNA bacteriophages that are prevalent and abundant in human feces and sewage. We assessed the performance characteristics of a crAssphage quantitative PCR (qPCR) assay for quantifying sewage impacts in stormwater and surface water in subtropical Tampa, Florida. The mean concentrations of crAssphage in untreated sewage ranged from 9.08 to 9.98 log10 gene copies/L. Specificity was 0.927 against 83 non-human fecal reference samples and the sensitivity was 1.0. Cross-reactivity was observed in DNA extracted from soiled poultry litter but the concentrations were substantially lower than untreated sewage. The presence of the crAssphage marker was monitored in water samples from storm drain outfalls during dry and wet weather conditions in Tampa, Florida. In dry weather conditions, 41.6% of storm drain outfalls samples were positive for the crAssphage marker and the concentrations ranged from 3.60 to 4.65 log10 gene copies/L of water. After a significant rain event, 66.6% of stormwater outlet samples were positive for the crAssphage marker and the concentration ranged from 3.62 to 4.91 log10 gene copies/L of water. The presence of the most commonly used Bacteroides HF183 marker in storm drain outfalls was also tested along with the crAssphage. Thirteen samples (55%) were either positive (i.e., both markers were present) or negative (i.e., both markers were absent) for both the markers. Due to the observed cross-reactivity of this marker with DNA extracted from poultry litter samples, it is recommended that this marker should be used in conjunction with additional markers such as HF183. Our data indicate that the crAssphage marker is highly sensitive to sewage, is adequately specific, and will be a valuable addition to the MST toolbox.

Evaluation of Two Entomopathogenic Fungi for Control of Culex quinquefasciatus (Diptera: Culicidae) in Underground Storm Drains in the Coachella Valley, California, United States.

Commercially available formulations of two entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Clavicipitaceae) and Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae), were assessed for control of Culex quinquefasciatus Say (Diptera: Culicidae) in underground storm drain systems (USDS) in the Coachella Valley of southern California. Each of three treatments, the two fungi or a water control, was applied to 1 m2 of vertical wall at eight USDS sites in spring and autumn of 2015. Fungal infectivity and lethality were assessed at 1 d and 1, 2, and 4 wk post-application. Overnight bioassays using adult lab-reared female mosquitoes were carried out on the treated USDS wall areas and then mosquitoes were held in the laboratory for up to 21 d to allow fungal infections to be expressed. Postmortem fungal sporulation was assessed up to 2 wk at 100% humidity. Mosquito-fungal interactions also were assessed in bioassays of the three treatments on filter paper exposed to USDS conditions during autumn. Metarhizium anisopliae killed mosquitoes faster than B. bassiana; nevertheless, both freshly applied formulations caused greater than 80% mortality. Fungal persistence declined significantly after 1 wk under USDS conditions, but some infectivity persisted for more than 4 wk. Beauveria bassiana was more effective against Cx. qinquefasciatus in the spring, while M. anisopliae was more effective in the cooler conditions during autumn. USDS environmental conditions (e.g., temperature, relative humidity, standing water) influenced fungal-related mortality and infection of Cx. quinquefasciatus. The utility of these fungal formulations for mosquito abatement in the Coachella Valley and implications for fungal control agents in USDS environments are discussed.

Oxidation of iron sulfide and surface-bound iron to regenerate granular ferric hydroxide for in-situ hydrogen sulfide control by persulfate, chlorine and peroxide

Hydrogen sulfide emission from sediments in storm drainage networks, estuaries and marine seafloor is a nuisance. The regeneration of the GFH for reuse is crucial to make dosing granular ferric hydroxide (GFH) an effective, long-lasting solution than doing liquid oxidants to the control of sedimentary hydrogen sulfide. This paper investigated the oxidation of iron sulfide and surface-bound iron compounds to regenerate GHF using persulfate, chlorine and peroxide for the in-situ control of hydrogen sulfide. The hydrogen sulfide removal capacities of virgin, persulfate-, chlorine- and peroxide-regenerated GFH were 68.34, 77.49, 67.87 and 57.59 mg S/g, respectively. The recovery of the capacities was mainly attributed to the oxidation of iron sulfide, surface-bound Fe(II) and released Fe2+ to amorphous ferric hydroxides. Iron sulfide was mainly oxidized to sulfate (SO42−) (97.8%) by persulfate, and to elemental sulfur (S(0)) (5.8 and 25%), thiosulfate (S2O32−) (27.7 and 11.3%) and SO42− (66.5 and 63.7%) by chlorine and peroxide, respectively. In addition to the oxidation by persulfate, the reaction between persulfate and the surface Fe(II) compounds also generated sulfate radicals and hydroxyl radicals, which enhanced the oxidation of the iron sulfide and surface-bound iron compounds on the GFH surface and regenerated GFH more completely.

Urban Flood Simulation Using Synthetic Storm Drain Networks

Recent developments in urban drainage modelling allow for a more realistic coupling of the two-dimensional (2D) surface and one-dimensional (1D) sub-surface drainage domain exchanging water through storm drain inlets instead of a sub-catchment approach based on manholes. Experience has shown, however, that comprehensive records of storm drain inlet locations are often missing or incomplete, preventing users accessing the full benefit of these modelling capabilities. Therefore, this study developed a GIS routine to generate synthetic storm drain inlet locations for the purpose of urban flood modelling. Hydrodynamic model results for a synthetically generated and surveyed storm drain inlet network were obtained using the CityCAT 1D/2D system. On a catchment scale the flow field (surface and flow captured by inlets) simulated by the network of synthetic storm drainage inlets shows satisfactory results when compared with that simulated using the actual network. The results also highlight the sensitivity of the inflows to relatively small changes in terms of the location of storm drain inlets and the effectiveness of storm drain inlets in ponding areas.

Characterization of Rainwater Drainage Infrastructure in the City of Lomé (Togo, West Africa)

Despite Togo government’s efforts to maintain and expand its storm drainage networks, urban flood disasters remain recurrent. Beyond Shallow zones occupation for construction and climatic causes, it is essential to circumscribe the determinants linked to infrastructure. Based on the inventory and characterization of rainwater drainage infrastructure, this study is a contribution to the reduction of flood risk in the city of Lome in Togo. Surveys were conducted on rainwater drainage works of the 172 paved roads in Lome. A sample of each network group is selected by considering the areas of recurring hazards and broadest catchment areas in the city for the evaluation of their structural and functional states according to the readapted VIZIR method. The relationship between these two states was computed using multiple correspondence analysis (MCA). This study reveals notable insufficiencies in rainwater drainage management in the city, expressed by the existence of roads built without drains, gutters without outlets, and open gutters and makeshift trenches built by the population. Functionally and structurally, almost all the structures are constructed of reinforced concrete. The most cracked are the mainly open pit (92.02%) works of the lagoon complex. The retention basin network includes 36 retention ponds 18 of which are interconnected, 11 drained by gravity and 4 by pumping. The latter are inherently hazardous insofar as pumping energy is not guaranteed. The MCA has shown that the network of piping related to the retention ponds are in similar conditions, and that generally, the closed gutters are not cracked while the open gutters are cracked.