Evaluation of the effect of super adsorbent and vegetation on green roof in cold dry climate

Urbanization in the world is increasing and the world's urban population is becoming denser in cities. One of the effects of urbanization is to increase the percentage of impermeable surfaces in these areas. Today, many important cities in the world, to reduce the effects of their city development on the quality and quantity of runoff, pay attention to the concept of sustainable development and use modern green management technologies, including the Best Management Practices (BMP) and Low Impact Development (LID) methods. Green roof is a multi-layer system that covers the roof and balcony of a building with vegetation and absorbs and retains part of the rain, and affects the processes of evapotranspiration, treatment, volume and intensity of runoff peak runoff. Reduces the dimensions of the downstream drainage system and improves the quality of the climate, preserves the beauty of the city and prevents wastage of building energy.

This study was conducted as a field experiment in the Faculty of Agriculture, University of Zanjan. The test period was from April to August 2018. In this study, the effect of using superabsorbent (zeolite) on water uptake and retention, maximum and minimum runoff volume, drainage volume, sedimentation and runoff time of rainfall at rainfall intensities of 35, 45, 55, 65 and 75 mm/hr on a green roof with a slope of 5% has been studied in cold dry climates.

Accordingly, with increasing rainfall intensity, runoff volume also increases and runoff volume in barren soil is more than other treatments and its downward trend is soil containing 1% zeolite, soil containing 3% zeolite and cultivated soil, respectively. Also, the volume of drainage increased with increasing rainfall intensity and the highest amount of drainage volume belongs to barren soil. Sediment measured in runoff also increases with increasing rainfall intensity in treatments other than grass treatment.

Barren soil has a very high runoff volume due to the closure of its surface layers and clogged pores. Addition of zeolite to the soil significantly reduced runoff volume and retained more water than barren soil. The rate of soil erosion was high in 1% zeolite and the lowest rate of erosion was in grass. In barren soils, infiltration is low, and runoff flows rapidly, but with the addition of zeolite to the soil, runoff start time is 3 % longer.