Exploring the effects of geotextiles in the performance of highway filter drains

Highway Filter Drains (HFD) are one of the most utilised drainage systems for roads, being considered as an environmental solution for sustainable drainage in transport infrastructures. However, little research has been done to understand their performance, representing a significant knowledge gap. This article therefore determines the hydraulic and clogging response of 3 different HFD designs in the laboratory; one standard design with British Standard Type B aggregate, and 2 new designs including a geotextile located at 50 mm and 500 mm depth from the surface of the HFD structure in order to assess the effect of the geotextile. The laboratory models were initially subjected to 9 rainfall scenarios with 3 rainfall intensities (2.5, 5 and 10 mm/h) and 3 storm durations (5, 10 and 15 min). Subsequently, the equivalent of 2-years' worth of pollutants were added to test possible clogging issues under the highest intensity rainfall event, corresponding to a 1 in 1 year return period for the West Midlands, UK. No clogging issues were found in any of the models although the majority of the sediments were concentrated in the first 50 mm of the HFD profile, with higher percentages (>90% of the sediment added) in those models with an upper geotextile. Location of the geotextile significantly influenced (p-value = 0.05) the hydraulic performance of the HFD.