The rain gardens at Bryggen in Bergen, Western Norway, is designed to collect, retain, and infiltrate surface rainfall runoff water, recharge the groundwater, and replenish soil moisture. The hydraulic infiltration capacity of the Sustainable Drainage System (SuDS), here rain gardens, has been tested with small-scale and full-scale infiltration tests. Results show that infiltration capacity meets the requirement and is more than sufficient for infiltration in a cold climate. The results from small-scale test, 245–404 mm/h, shows lower infiltration rates than the full-scale infiltration test, with 510–1600 mm/h. As predicted, an immediate response of the full-scale infiltration test is shown on the groundwater monitoring in the wells located closest to the infiltration point (<30 m), with a ca. 2 days delayed response in the wells further away (75–100 m). Results show that there is sufficient capacity for a larger drainage area to be connected to the infiltration systems. This study contributes to the understanding of the dynamics of infiltration systems such as how a rain garden interacts with local, urban water cycle, both in the hydrological and hydrogeological aspects. The results from this study show that infiltration systems help to protect and preserve the organic rich cultural layers below, as well as help with testing and evaluating of the efficiency, i.e., SuDS may have multiple functions, not only storm water retention. The functionality is tested with water volumes of 40 m3 (600 L/min for 2 h and 10 min), comparable to a flash flood, which give an evaluation of the infiltration capacity of the system.
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Permeable pavements are a type of SUDS that are becoming more common to allow infiltration, to minimize runoff volumes and to treat urban water stormwater by soil filtration. However, urban stormwater runoff contains significant concentrations of suspended sediments that can cause clogging and reduce the infiltration capacity and effectiveness of permeable pavements. This study used a full-scale infiltration test procedure to evaluate the infiltration performance of 20 permeable pavements that have been in service for over 2 to 9 years in the Netherlands. The observed infiltration capacities range between 20 and 342 mm/h.
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Over the past decades, various types of permeable pavements have been implemented in different municipalities in the Netherlands in order to improve infiltration capacity in urban areas and therewith being able to better treat stormwater runoff. With initial promising results, this adaptation measure seemed to be the solution for urban flooding due to extreme precipitation.However, in practice, foreseen infiltration capacities were usually not met, often due to unknown reasons. To better understand the functioning of permeable pavements in practice, we have studied - as part of the project Infiltrating Cities - over 100 existing permeable pavement installations in the Netherlands. At each location, infiltration capacity was tested through a full-scale infiltration testing procedure (flooded area about 40 m2) while conditional on-site factors were collected (location, age, type of permeable pavement, street-type, traffic density, vicinity of urban green, regular maintenance regime, etc.). By coupling this information we analyzed how these factors influence the infiltration capacity of permeable pavements in practice, e.g. through accelerated deterioration of infiltration capacity through time. In addition, we evaluated for a selected number of installations, how various types of maintenance may counteract this deterioration, hence improving the infiltration capacity of permeable pavements.
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