Deyvid Wavel Barreto Rosa

Standardized design criteria and performance assessment of parcel-level on-site stormwater detention (OSD) remain limited. This study evaluates the hydrological impact of OSD — designed per Belo Horizonte’s (Minas Gerais, Brazil) municipal guidelines — at both parcel and catchment scales using hydrological modeling in a highly impervious, flood-prone subcatchment. Results indicate that while existing guidelines are generally effective, volume sizing could be optimized. OSD implemented across 31.8% of the catchment significantly reduced peak flows, though effectiveness varied by spatial scale. At the parcel level, outflows decreased by 72.3% for 2-year and 50.7% for 100-year return period rainfalls, with delay in peak times of 41.7%. At the catchment level, peak flow reductions reached 24.6% (2-year) and 26.4% (100-year). Flow routing at the catchment outlet revealed reductions in channel overflow volumes and maximum water heights by 75.5%, 54%, and 49% for 2-, 10-, and 50-year events, respectively.

This paper aims to evaluate the hydrologic impacts of urban expansion in a peri-urban catchment that drains into a reservoir of the drinking water supply system of Belo Horizonte Metropolitan Region in Brazil. Despite the metropolitan interest and efforts in protecting the catchment, a recent change in zoning ordinances allowed urban expansion in the area. To evaluate the potential hydrological impacts of this land use regulation change, scenarios of urban expansion were conceived and simulated in the model Dinamica EGO. The Storm Water Management Model (SWMM) was employed to assess potential hydrological impacts of land use change projections. Observed precipitation and water level data of the reservoir were used to calibrate and validate the hydrological model. Results confirm the impacts on several catchment hydrological processes following the progressive urban expansion in the area, particularly on volumes of infiltration, groundwater flow and runoff, increasing peak flows and flooding downstream the reservoir.

Green and blue infrastructure (GBI) is an urban planning approach that can reduce and mitigate the impacts of urbanization in the water cycle. This study evaluates the hydrologic impacts of a possible deployment of GBI in a peri-urban catchment under pressure from urban development. Considering cost-effectiveness, the best combinations of GBI techniques were simulated and compared with a scenario with urban expansion. A hydrological model in SWMM was applied to simulate impacts of GBI in runoff and a Hec-RAS model to assess the impact on flood. A combination of lot areas treated by rooftop disconnection and roads treated by vegetative swales achieved the lowest cost and one of the highest effectiveness in runoff reduction. Despite the growth of impervious area by almost 100% from urban expansion, the GBI scenario would bring the hydrological conditions and total flooded area downstream closer to the current scenario ones.

Intense urbanization results in greater soil sealing and a consequent increase in surface runoff. When high soil sealing rates and high slopes are encountered in small catchments, high volume and short duration precipitation events increase the probability of flash floods. This study evaluates the hydrological response of an urban catchment with regard to rainfall-runoff events in the following scenarios: current land use, without a detention basin which has been part of the system since the 1970s, with the maximum soil sealing allowed by legislation, and with green infrastructure implantation in 100%, 50% and 10% of the suitable area. Hydrological modelling was performed using the Storm Water Management Model (SWMM). Six level gauges installed along the length of the stream provided the data used in model calibration and validation. The model calibration process provided adequate results: the average Nash-Sutcliffe coefficient was 0.72, the mean error of peak flow was 11% and the mean error of the runoff volume was 12%. Rainfall based on 2-, 10-, 50- and 100-year events were simulated for each scenario, as well as two observed events. In the scenario without the detention basin, an average elevation of 10% in the peak flow was observed in the catchment outlet. In the scenario with maximum soil sealing, the catchment outlet peak flow increased by 30% on average. On the other hand, in the scenario with green infrastructure implementation in 100%, 50% and 10% of the available areas, the outlet peak flow was reduced by 60%, 30% and 5%, respectively. Results indicated the efficiency of the detention basin to reduce flooding, the importance of green area preservation to reduce peak flows, as well as the catchment potential of green infrastructure implementation and the hydrological benefits that they can provide, increasing infiltration and reducing runoff volume and peak flow.