Urban Runoff Management Research Articles

Application of Bio-pore Infiltration Hole as an Urban Runoff Management

The application of bio-pore infiltration holes (BIH) can be one solution for urban runoff management by reducing surface runoff to the ground. But, the difference in soil types and characteristics could affect the runoff reduction that can be achieved by BIH. This research aims to determine the runoff reduction can be achieved by bio-pore infiltration hole (BIH) from different soil types and conditions. The methods in this study mainly focus on hydraulic conductivity calculations using Porchet method and the implementation of Minister of Environment Regulation Numb. 12/2009 for the BIH installations. Based on the implementation of Minister of Environment Regulation Numb. 12/2009, the required BIHs for the area of 500 m2 are 1,000, both for silt and clay soils. The runoff reductions that can be achieved with the application of BIHs are 38.98 - 95.73% for silt soils and 20.67 - 54.28% for clay soils, depends on the soil conditions

The Role of Constructed Wetlands as Green Infrastructure for Sustainable Urban Water Management

Nowadays, it is better understood that the benefits of green infrastructure include a series of ecosystem services, such as cooling, water storage and management, recreation and landscaping, among others. Green technologies are still developing to provide sustainable solutions to the problems that modern cities and peri-urban areas face at an ever-increasing rate and intensity. Constructed wetlands technology is an established green multi-purpose option for water management and wastewater treatment, with numerous effectively proven applications around the world and multiple environmental and economic advantages. These systems can function as water treatment plants, habitat creation sites, urban wildlife refuges, recreational or educational facilities, landscape engineering and ecological art areas. The aim of this article is to highlight the synergies between this green technology and urban areas in order to reconnect cities with nature, to promote circularity in the urban context and to apply innovative wetland designs as landscape infrastructure and water treatment solutions. This approach could be a step further in the effort to mitigate the current degradation process of the urban landscape. Following the concept of green infrastructure, the article presents and suggests ways to integrate wetland technology in the urban environment, namely: (i) stormwater and urban runoff management (storage and treatment of water during storm events) to provide protection from flood incidents, especially considering climate change, (ii) innovative low-impact infrastructure and design solutions for urban wastewater treatment, and (iii) wetland technology for habitat creation and ecosystem services provision.

Multi-objective decision-making for green infrastructure planning (LID-BMPs) in urban storm water management under uncertainty

Sustainable urban surface runoff management is receiving increased attention due to environmental and ecological consequences related to urbanization. This study presents a useful new framework for green infrastructure (GI) planning for the management of urban runoff quality and quantity. The proposed framework considers physical, technical, economic, and multi-stakeholder aspects related to urban runoff management while simultaneously addressing the uncertainties of the decision-making process and model parameters. The methodology is applied to regionally locating and sizing low impact development-best management practices (LID-BMPs) while considering the hydrologic and hydraulic impacts. A decision-making multi-objective optimization framework is developed by integrating: 1) a Multi-Layer Perceptron neural network founded on a Storm Water Management Model (SWMM-MLP meta-model), 2) NSGA-II multi-objective optimization, 3) fuzzy α-cut technique, and 4) a decision-making support model based on social choice theory to elicit trade-offs among system cost and LID-BMP performance indicators. The decision-making model, based on Fuzzy Social Choice (FSC) theory, is applied to simulate consensus between stakeholders for a partially cooperative group decision-making problem. The proposed methodology is explored in a catchment located in the northeastern part of Tehran, Iran. Results showed that the SWMM could be effectively replaced with a MLP-based meta-model in simulation-optimization problems for urban runoff management. In the application of FSC methods, the optimal scenarios were effective in reducing the volume of urban runoff and contamination loads while maintaining the optimality of the operation costs. Considering the optimal LID scenario, a reduction of more than 99% in runoff volume and biochemical oxygen demand (BOD), and a decrease of more than 92% of total suspended solids (TSS), occurred for the lower bound of uncertainty (lower (left) end of the α-cut = 0.3). For the upper bound of uncertainty (upper (right) end of the α-cut level = 0.3), a maximum reduction of 57% was obtained. In applying FSC methods through the decision-making process, the Borda Counting method considered the preferences of all stakeholders best. Moreover, the proposed framework allows decision-makers to decide on the acceptability and reliability of the optimal management scenarios considering their preferences and uncertainties.

Effect of photocatalytic Fe2O3 nanoparticles on urban runoff pollutant removal by permeable concrete

Permeable pavements are an efficient urban runoff (UR) management solution that also improve water quality. In this work, a photocatalytic layer of Fe2O3 nanoparticles (NP) was incorporated into permeable concrete to evaluate its impact on the removal of several microbiological (Escherichia coli, Pseudomonas aeruginosa, Aeromonas hydrophila, and Enterococcus faecalis) and physicochemical (N-NH4+, N-NO3-, phenol, PO43−, Fe, Mn, and Pb) pollutants. First, permeable concrete samples were created with sufficient compressive strength and hydraulic conductivity for light traffic. The test samples were then coated with a mixture containing either 3% or 5% Fe2O3 NP by cement weight. Control samples were prepared without NP. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy analyses showed that the nanoparticles remained unaltered on the concrete's surface. Synthetic URs simulating the microbiological or physicochemical composition of real UR were applied to the samples to evaluate their pollutant removal efficiencies. The depollution performances of the test (with 3% and 5% Fe2O3 NP) and control samples were statistically compared. The test samples (3% NP, 5% NP, and the controls) significantly modified (p < 0.05) most of the measured variables (i.e., the concentrations of E. coli, A. hydrophila, PO43−, Fe, Mn, and Pb) in the synthetic URs. Unexpectedly, the test samples (with 3% or 5% Fe2O3 NP) did not significantly remove (p > 0.05) some pollutants prone to oxidation, such as phenol or ammonium. However, the 5% NP sample significantly enhanced Mn removal. In general, the decontamination performances of the concrete samples with Fe2O3 NP were not influenced by the nanoparticles; thus, they did not appear to add value to the generated permeable concrete. Nevertheless, our results indicate the considerable benefits of implementing permeable concrete to improve the quality of UR.

Occurrence of microcystin-LR in vegetated lagoons used for urban runoff management

Phytoremediation with aquatic macrophyte has been considered as an eco-friendly technique for controlling harmful cyanobacteria outbreak and proven to be effective. The conventional water quality parameters are frequently measured to evaluate the effectiveness of phytoremediation. However, the concentration of microcystin-leucine-arginine (MC-LR) in different vegetated water still remains uncertain. In this study, the contents of MC-LR in four macrophyte-vegetated lagoons were determined by solid phase extraction and ultra-high-performance liquid chromatography with tandem mass spectrometry technology. Results indicated that MC-LR was found in Nymphaea tetragona lagoon (lagoon-S), Vallisneria spiralis lagoon (lagoon-B) and another Vallisneria spiralis lagoon (lagoon-J). Only in lagoon dominated by Pistia stratiotes L. (lagoon-D), MC-LR concentration was undiscovered regardless of seasonal variation. The levels of MC-LR varied seasonally and were affected by the different vegetated aquatic macrophytes. The results suggest that in addition to conventional physicochemical parameters and indicators of water quality, MC-LR levels should be taken into consideration when the effectiveness of phytoremediation is assessed.

Assessment of stormwater pollutant loads and source area contributions with storm water management model (SWMM)

Decentralized urban runoff management requires detailed information about pollutant sources and pathways. However, scarce data of local water quality compel simplified approaches in water quality modelling. This study investigated the use of constant source concentrations in modelling pollutant loads. The source area contributions of total suspended solids, total phosphorus, total nitrogen, lead, copper and zinc were modelled with SWMM based on literature event mean concentrations (EMCs) for different land cover types and on-site rainfall and discharge data for a residential area in southern Finland. The simulated pollutant loads were compared with loads measured at the catchment outlet. Large differences were evident in the modelled catchment-scale and land cover specific loads, depending on the EMC data source. The simulated loads exceeded the measured loads especially during wet conditions, which was explained by the dilution effect of large stormwater volumes on measured EMCs. In addition, the mismatch was explained by the lack of local data for the source area EMCs and by the unaccountability of the mechanisms affecting loads along the pollutant pathways from source areas to sewer outlet. The spatial simulation of stormwater pollutant loads enabled the assessment of source area contributions at the catchment scale, as well as the pollutant pathways and the total diffuse pollution load. For a single pollutant, one or two important pollutant sources contributed the majority of the catchment load, which provides useful information for stormwater management. However, for a group of pollutants, no single land cover type dominated the pollutant loads, reflecting the challenges in decentralized water quality management in the scale of a residential area. Overall, the results emphasize that the widely used stormwater quality modelling with constant EMCs is uncertain even when on-site water quality and rainfall-runoff data from a catchment outlet are available.

Site-Scale LID-BMPs Planning and Optimization in Residential Areas

Low-impact development best management practices (LID-BMPs) are a representative and effective approach in urban runoff management. In a planning process, it is important to optimally design and place LID-BMPs to maximize cost-effectiveness, and equally important to fully evaluate the planning’s control effects. This paper presents a case study of LID-BMPs planning and optimization in a residential community in China using SUSTAIN as the modeling tool. The LID-BMPs facilities are designed individually and placed at specific locations. Runoff volume and quality are simulated for predevelopment, basic, and planning scenarios. Optimization is conducted to reveal cost-effective schemes and to determine an optimal scheme that meets the control target. This optimization scheme achieves a 75.2% control rate with a cost of USD 1 million. In addition to the commonly used annual rainfall data, designed storm events are also input to further examine the control effects of the optimization scheme for rainfalls of different return periods. Results show that optimized site-scale LID-BMPs can provide benefits for a range of rainfall intensities, but are especially effective for short-return-period rainfall.

Water Quality and Three-Dimensional Fluorescence of Stormwater Runoff from Lined Bioretention Field Cells

Bioretention cells have become one of the most popular devices in urban stormwater runoff management for their high efficiency in reducing runoff volume and pollution loads. However, bioretention cells are unstable in nutrient pollutant removal, as is verified by many cases, especially at low temperatures. Dissolved organic matters (DOMs) plays an important role in denitrification, but the three-dimensional fluorescence characteristics of stormwater runoff in bioretention field cells are poorly understood, so to improve the performance of bioretention cells in nutrient pollutants control, the authors determined that it was necessary to clarify the characteristics of three-dimensional fluorescence of stormwater runoff from bioretention cells and explain their relationship to water quality. To be applicable to urban landuse in mountainous cities, two field lined bioretention cells were constructed, and, from March to April in 2017, while temperatures were still low, water quality and three-dimensional fluorescence of stormwater runoff were analyzed during low rainfall intensity precipitation events. Analysis results showed that the effluent pollutant concentrations had low fluctuation after purification by the bioretention cells, and both cells showed relatively stable removal rates for NH4+-N and total phosphorus (TP; i. e., 78.38%-95.03% and 72.04%-76.04%, respectively). Analysis of fluorescence spectra showed that the DOMs in the runoff from the two cells was mostly made up of protein and humic substances, mainly of biological origin or aquatic bacterial metabolites. Both cells performed well in the removal of protein at I, protein at Ⅱ and fulvic acid (i. e., the removal rates could reach 57.33%-61.30%, 29.82%-31.28%, and 35.55%-43.16% respectively). Correlation analyses between water quality and DOM showed that total Nitrogen (TN), TP and total organic carbon (TOC) were positively correlated with the protein content in runoff from the biorentention cells, while NO3--N and NH4+-N were negatively correlated with protein content. Meanwhile, TN was negatively correlated with DOMs in regions Ⅳ and Ⅴ of the cells.

Technological Review of Permeable Pavement Systems for Applications in Small Island Developing States

This paper presents a technological review of permeable pavement systems (PPS) for applications in urban areas of small island developing states (SIDS). This review includes a literature survey of PPS, challenges and opportunities of climate change and urban development in SIDS, and key aspects worth considering for widespread acceptance and use of PPS in SIDS. SIDS is comprised of several nations located across the Atlantic, Pacific, and Indian Oceans, as well as the Caribbean, Mediterranean, and South China seas. They are particularly susceptible to the effects of climate change and increasing urbanization. Urban stormwater management and flooding are often serious challenges faced by authorities in most SIDS. PPS are resilient infrastructure which can assist in mitigating flooding by reducing runoff and peak flows and improving the landscape perviousness. PPS can further improve stormwater runoff quality to receiving natural waters by reducing pollutant loadings of suspended solids, heavy metals, and hydrocarbons. Unlike most territorial states, the geographical and geologically confined nature of most SIDS present unique parameters for consideration when designing permeable pavements for SIDS. This literature survey found that some of the most important parameters include traffic loads, cost, construction aggregate choice, and availability, permeability of existing soil at the intended location, depth of water table, potential for groundwater contamination, slope of the pavement, stormwater reuse option, clogging, maintenance, and support from policy makers. Continued practical research into the use of permeable pavements for urban runoff management in SIDS is on‐going with the expectation of PPS being utilized in many SIDS.

Correction to: Influence of Biochar from Slow Pyrolysis on Dissolved Organic Carbon and Total Dissolved Nitrogen Levels of Urban Storm-Water Runoff

Biochar as a filtering media has been attracted increasing attention for applications in urban storm-water runoff (USWR) management. Up-flow percolation tests were conducted with pine bark (PB) and biochars from PB (BCPB) for evaluating changes in dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations varying with pyrolysis temperatures (i.e., 300, 450, and 700 °C) and types of USWR (i.e., roof and pathway USWR). The most suitable pyrolysis temperature for limiting DOC leaching from BCPB depends on the types of USWR. For all the adopted pyrolysis temperature, BCPB released cumulative amount of DOC up to 0.01% of the TC content in the up-flow percolation tests with pathway USWR. High-temperature (i.e., 700 °C) BCPB released lower cumulative amount of DOC (up to 0.02% of the TC content) compared to the low-temperature (< 450 °C) BCPB in the roof USWR up-flow percolation tests. As for BCPB effectiveness in carbon sequestration, the amount of carbon that is not retained in BCPB because of leaching (DOC less than 0.1% of the TC content) may be considered negligible. Of the tested BCPB, only high-temperature BCPB removed TDN for both the types of USWR with cumulative removed quantities up to 0.006 g/kg dry weight, thus representing a better option for reducing N loads to receiving water basins.

Use of rainwater in urban areas and storm warter run-off quality management: environmental and economic aspects

The paper considers the reasons for deepening current problems of the surface waters and control of surface wastewater quality in the cities of Europe and the world; the analysis of climatic and other natural factors affecting the assessment of the feasibility of rainwater management projects in a particular city (by the case of Kharkiv) is carried out; the results of the study on the pressure on water bodies brought by the surface waters within the urban landscape geo-system are provided; ecological assessment of the water body is made. The analysis of long-term statistical data and review of the current literature on the subject indicates that there is a trend towards the increase in precipitation in European cities with a moderate climate and in some cities with a tropical one. Over the last 10 years extreme erratic intensity of rainfall, both in terms of monthly precipitation in the warm half-year (May–October), and in the total monthly and seasonal number of rainy days has become typical for Kharkiv. Moreover, there is a change in the precipitation patterns – a decrease in the number of moderate rains and an increase of thunderstorms, showers and hail. Applying modern methods, the amount of surface water in the city is estimated, taking into account the percentage of the city’s territory densely covered with water. The quality of surface waters is determined by means of chemical analysis; the pressure on water bodies through unorganized surface run-off surface runoff from the urban territory is determined and assessed. The article presents an overview of successful urban projects of rainwater harvesting, its retention and practical usage, taking into account the sources of financing and offers measures and recommendations on implementing blue economy projects in the conditions of some particular city.

Monetary value of urban green space as an ecosystem service provider: A case study of urban runoff management in Finland

The predicted increase in the number of urban flood events can result in substantial monetary losses to society. These costs may be alleviated by preserving ecosystem services, such as urban runoff management. We studied the monetary value of this ecosystem service by applying the replacement cost method in six catchments with varying land-use intensities in two cities in Finland. The economic analysis was based on metric data of urban runoff generation, provided by automatic monitoring stations in the catchments. A hydrological model was applied to estimate evaporation from impervious surfaces, and to simulate runoff in the catchments. Our results suggest that leaving green space unconstructed results in significant monetary savings. The cost of managing runoff correlated with land-use intensity. The ecosystem service value (ESV) was generally higher in catchments with high land-use intensity, low proportion of green space, and high costs of runoff management. Depending on the degree of imperviousness, the ESV ranged from 90,000–270,000€ha−1. Further, our results suggest that estimates of runoff generation and evaporation are key hydrological factors for assessing ESV. Our study demonstrates how the combination of field data and hydrological and monetary analyses can support regional planning in cold climates.

Lykilþættir í innleiðingu blágrænna ofanvatnslausna á Íslandi

Existing urban drainage structures that collect stormwater in underground piping networks face increased pressure with urban densification and increased rainfall intensity with global warming. Urban flooding may become more frequent in the future posing economic, environmental and health risks. Sustainable Drainage Solutions (SuDS) are increasingly being considered as a natural and economical approach to surface water management. Ponds, vegetated swales, rain gardens and green roofs slow down the surface water flow and break down pollutants stemming from traffic, asphalt wear and roof materials. SuDS has been designed for one neighbourhood in Iceland, Urriðaholt. The Icelandic Planning Act and National Planning Strategy have set the base for the implementation of SuDS. Iceland, however, lacks a comprehensive strategy to obtain the benefits of SuDS. This article presents the key success factors for implementing SuDS in Iceland, based on a review of Sweden's and England ́s decadal experience, and current legal, planning, knowledge and data environment in Iceland. Firstly, it is important to clarify the strategic goals of urban runoff management in governmental policy documents. Secondly, the implementation of SuDS needs to be intertwined with the planning process both in municipal and detailed planning phases. A collaborative effort must be undertaken between sewer specialists, planners and other professionals to develop novel surface water collection approaches with respect to local conditions. Collaboration, roles and responsibilities must be clear and identified throughout the SuDS life cycle, from strategy, planning and design, to construction, operation and maintenance. More interdisciplinary research needs to be conducted with regards to SuDS, and communicated to local stakeholders to improve their general knowledge on SuDS.

Determining the robust optimal set of BMPs for urban runoff management in data-poor catchments

Mismanagement of urban runoff can result in inundation which causes serious problems in providing urban services. Best management practices (BMPs) are used for urban runoff management. In this study, a method is proposed to determine the robust optimal set of BMPs for runoff management in data-poor catchments in urban areas. This method includes five main steps: (1) Sensitivity analysis to determine effective parameters in rainfall-runoff simulation model, (2) Calibration of the rainfall-runoff model based on selected effective parameters, (3) Developing a multi-objective optimization model to obtain the optimal sets of BMPs, (4) Selecting the final solutions using the Nash approach for ranking, (5) Evaluation of the robustness of the selected solution using the Management Option Rank Equivalence method. The proposed method is examined in an urban basin located in the north of Tehran, Iran. The results show that the proposed approach provides reliable results for urban runoff management in data-poor areas.

A multi-stakeholder framework for urban runoff quality management: Application of social choice and bargaining techniques

In this paper, an integrated framework is proposed for urban runoff management. To control and improve runoff quality and quantity, Low Impact Development (LID) practices are utilized. In order to determine the LIDs' areas and locations, the Non-dominated Sorting Genetic Algorithm-II (NSGA-II), which considers three objective functions of minimizing runoff volume, runoff pollution and implementation cost of LIDs, is utilized. In this framework, the Storm Water Management Model (SWMM) is used for stream flow simulation. The non-dominated solutions provided by the NSGA-II are considered as management scenarios. To select the most preferred scenario, interactions among the main stakeholders in the study area with conflicting utilities are incorporated by utilizing bargaining models including a non-cooperative game, Nash model and social choice procedures of Borda count and approval voting. Moreover, a new social choice procedure, named pairwise voting method, is proposed and applied. Based on each conflict resolution approach, a scenario is identified as the ideal solution providing the LIDs' areas, locations and implementation cost. The proposed framework is applied for urban water quality and quantity management in the northern part of Tehran metropolitan city, Iran. Results show that the proposed pairwise voting method tends to select a scenario with a higher percentage of reduction in TSS (Total Suspended Solid) load and runoff volume, in comparison with the Borda count and approval voting methods. Besides, the Nash method presents a management scenario with the highest cost for LIDs' implementation and the maximum values for percentage of runoff volume reduction and TSS removal. The results also signify that selection of an appropriate management scenario by stakeholders in the study area depends on the available financial resources and the relative importance of runoff quality improvement in comparison with reducing the runoff volume.

Protocols for Studying Wet Weather Impacts and Urbanization Patterns

This research study explores the relationship of urbanization to ecology in the wadeable streams of developing watersheds and describes a protocol, which urban stormwater management agencies can apply in their jurisdiction, to prevent the severe ecologic deterioration that presently occurs in urban streams as a watershed develops. The protocol comprises an 8-step process that involves data collection and analysis integrated with mathematical modeling of runoff from existing and proposed urban development to determine how biologic health indices such as the benthic index of biotic integrity (B-IBI) or Ephemeroptera, Plecoptera, Trichoptera (EPT) richness responds to urbanization of a watershed. Stormwater managers can apply this protocol in their areas of jurisdiction to assist them in developing urban runoff management rules and design criteria with some assurance that the resulting development will minimize negative impacts on the ecology of receiving streams. In addition to the full protocol, a simple protocol is also provided for municipal agencies to use that does not require extensive data collection. This title belongs to WERF Research Report Series ISBN: 9781780403663 (eBook) ISBN: 9781843397878 (Print)

Mathematical Model for Sediment Wash-Off from Urban Impervious Surfaces

AbstractMathematical models are significant tools for urban runoff management. A rational account of sediment-limited and energy-limited situations in developing a mathematical model may facilitate the improved simulation of total suspended solid (TSS) wash-off in urban impervious surfaces. In this study, a differential equation called the P/r model is proposed to improve the simulation of the sediment discharge process. In this equation, rainfall intensity and the ratio of sediment mass per unit catchment area to rainfall intensity are considered the main variables. The rationality behind the P/r model is analyzed. TSS wash-off from six rainfall events is investigated using the P/r model. Uncertainty analyses are performed to determine the best-fit parameters for the model, with the maximum Nash–Sutcliffe efficiency (NSE) criterion being 0.53 and the minimum normalized objective function being 0.40. The observation percentage within prediction bands is 75%, and the average relative interval length is 1.0...

Developing a stochastic conflict resolution model for urban runoff quality management: Application of info-gap and bargaining theories

Summary In this paper, two deterministic and stochastic multilateral, multi-issue, non-cooperative bargaining methodologies are proposed for urban runoff quality management. In the proposed methodologies, a calibrated Storm Water Management Model (SWMM) is used to simulate stormwater runoff quantity and quality for different urban stormwater runoff management scenarios, which have been defined considering several Low Impact Development (LID) techniques. In the deterministic methodology, the best management scenario, representing location and area of LID controls, is identified using the bargaining model. In the stochastic methodology, uncertainties of some key parameters of SWMM are analyzed using the info-gap theory. For each water quality management scenario, robustness and opportuneness criteria are determined based on utility functions of different stakeholders. Then, to find the best solution, the bargaining model is performed considering a combination of robustness and opportuneness criteria for each scenario based on utility function of each stakeholder. The results of applying the proposed methodology in the Velenjak urban watershed located in the northeastern part of Tehran, the capital city of Iran, illustrate its practical utility for conflict resolution in urban water quantity and quality management. It is shown that the solution obtained using the deterministic model cannot outperform the result of the stochastic model considering the robustness and opportuneness criteria. Therefore, it can be concluded that the stochastic model, which incorporates the main uncertainties, could provide more reliable results.

Hydrologic Performance of a Transitioned Infiltration Basin Managing Highway Runoff

AbstractInfiltration basins are widely used stormwater control measures (SCMs) for urban stormwater runoff management. However, these SCMs can experience progressive failure to hydrologically perform as originally designed (i.e., primarily infiltration-based runoff control) and the functionality of such failed infiltration basins in managing stormwater runoff is unknown. In this field-scale research study, the hydrologic performance of a failed stormwater infiltration basin was investigated over 3 years. Visual indications of wet pond/wetland like conditions on-site suggested that the infiltration basin had evolved or transitioned to an alternate type of SCM. The transitioned infiltration basin mitigated runoff flows by providing dynamic flow attenuation, total volume and peak flow reductions, and reduced discharge durations. Performance of the transitioned basin can be classified into the following three hydrologic regimes: 100% volume reduction due to complete capture for small storm events; variable vo...

Impacts of urban development on runoff event characteristics and unit hydrographs across warm and cold seasons in high latitudes

Summary The impacts of urbanization on catchment hydrology are widely studied by comparing how different urban catchments respond to storm events, but rarely by realizing long-term observations of hydrological changes during the construction process at urbanizing small catchments. In this study, the changes occurring in runoff generation were monitored in a developing catchment under construction and in two urban control catchments. As the imperviousness of the developing catchment increased from 1.5% to 37%, significant increases were observed in event runoff depths and peak flows during rainfall–runoff events. At the same time, the only statistically significant changes that were observed for the cold period runoff events were the shorter duration and smaller runoff depths. The effect of urbanization on event runoff dynamics was studied in terms of changes in the instantaneous unit hydrographs (IUH). Negative trends were detected in the gamma parameters of IUHs, which became more consistent across events and produced a sharper shape of the hydrograph as the construction works progressed. Because urban development caused the greatest relative changes in runoff during frequently occurring minor rainfall events, the study results underlined the importance of small storms in urban runoff management for maintaining the predevelopment water balance. During infrequent major rainfall events and the cold period snowmelt events the impacts of urbanization were less pronounced. The impact of urbanization on runoff was best detected based on peak flow rates, volumetric runoff coefficients, or mean runoff intensities. Control catchments were essential to distinguish the hydrological impact caused by catchment characteristics from those caused by changes in the meteorological conditions or season.