Binod Baniya^1,, Kua-anan Techato², Sharvan Kumar Ghimire³, Gyan Chhipi-Shrestha⁴

Urban temperature has been escalating less greenery and high built up areas. More than half of the total population is residing in urban area so that the urban environment is highly vulnerable. Restoration of urban forestry is very expensive and almost not possible as they have already used the massive land for development purpose. In this context, green roofs technology has rapidly emerged. It has multifaceted environment, aesthetic and social benefits. It absorbs atmospheric carbon, mitigate urban heat and cool the surface temperature which reduces the energy demand and cost. Because of these several environmental benefits, green roofs can be practiced in Kathmandu. The Kathmandu, one of the fastest growing city in south Asia faces several and catastrophic environmental problems related to urban heat. In this study, we reviewed the urban heat island, green roofs techniques and use of remote sensing and GIS extension model to study urban greenery and temperature. The MODIS NDVI, CRU climate and monthly temperature data from 8 meteorological stations during 2000-2016 were used. Mann Kendell test statistic and Sen’s slope were used for the analysis of temperature changes in Kathmandu valley. Beside it, the land use land cover data of 2010 were used and the previous literatures related on Kathmandu valley were reviewed. The air surface temperature has significantly increased at the rate of 0.04°C yr^-1 with a maximum temperature trend of 0.06°C. The average annual air surface temperature of Kathmandu valley is 18.06°C with maximum 24.15°C during 2000-2016. In contrary, average annual land surface temperature has ranges from 15.84°C-39.17°C in 2000 and 16°C to 33.98°C in 2014. At the same time, urban area has dramatically increased; averaged LST has more than air surface temperature, Normalized Difference Vegetation Index values has low but normalized difference built up index has high in core urban area. These all environmental consequences are the main factors of urban heat Island in Kathmandu valley. Therefore, green roofs could be an effective mitigation tool to combat environment problems and urban heat island. Though, detail investigation is required to practice green roofs in Kathmandu valley.

green roofs, urban heat island, environment, Kathmandu valley, Nepal