Marjo Valtanen

A high resolution application of a stormwater management model (SWMM) using genetic parameter optimization

Low Impact Development (LID) tools and green infrastructure approaches have been developed and applied to mitigate the urbanization impacts on increasing runoff and pollutant washoff. The present work is the first part of a larger effort to simulate LID scenarios for a large scale urban catchment through up-scaling of high-resolution study catchments using the Stormwater Management Model (SWMM). In this study we present the setup, calibration, validation, and the results of a parameter sensitivity analysis of a high-resolution SWMM model for a highly urbanized small catchment located in Southern Finland. The homogenous subcatchments and associated narrow parameter boundaries, which are allowed by the high spatial resolution, result in insensitivity of SWMM to the fraction of impervious cover. The model optimization, using only the two identified key parameters “depression storage” and “Mannings roughness n for conduit flow”, yielded good performance statistics for both calibration and validation of the model.

Spatio-temporal patterns of major ions in urban stormwater under cold climate

Department of Geosciences and Geography, University of Helsinki, Helsinki, Finland Department of Built Environment, Aalto University, Espoo, Finland Department of Environmental Sciences, University of Helsinki, Helsinki, Finland Correspondence Maija Taka, Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, FI‐00014 Helsinki, Finland. Email: maija.taka@helsinki.fi Funding information European Union Life + programthe Academy of Finland, Grant/Award Number: 263335. 263320. 263308.

Large-scale Urban Hydrological Modelling At High Spatial Resolution: Requirements And Applications

Urbanization and associated increase of imperviousness alters the hydrological cycle of urbanizing catchments. Low Impact Development (LID) tools have been developed and applied to mitigate these hydrological impacts. Hydrological models are one way to evaluate the performance of LID tools before their implementation. As these tools represent small-scale hydrological processes, hydrological models used in assessment require a high spatial and temporal resolution in their process descriptions. Both flow and rainfall data at high recording frequencies (e.g. 1 min) are usually not available for large urban catchments and detail in spatial data for surface description has to be complemented through on-site observations. Thus, the assessment of LID performance for large urban areas has to overcome these constraints. Previous studies provide suggestions to overcome the lack of flow data for model calibration through parameter regionalization. Recently presented methods for reductions in spatial resolution while maintaining a detailed surface description provide a feasible way to characterize large urban catchments for LID performance assessment. However, rainfall data at high temporal and spatial resolution remains a key element for hydrological model applications in urban areas. The authors evaluated the impact of spatial and temporal rainfall variability on model performance using the Stormwater Management Model (SWMM) and high-resolution parameterizations of three urban catchments in combination with two rain gauges. While the distance between rain station and catchment did not affect model parameters the authors found a reduction in model efficiency with an increasing rain station distance from the catchment.