Alleviating Heat Island Effect of Urban Artificial Rivers in Shijiazhuang, Hebei Province

As the urban heat island (UHI) effect has been intensified, cooling effect of urban artificial rivers has gradually gained more attention. Based on the remote sensing image of Shijiazhuang City on August 31, 2016, the cooling effect of the artificial Minxin River in the third ring road of Shijiazhuang City was evaluated by using buffer analysis method. The results show that: (1) The range of urban thermal field variation index (UTFVI) within the third ring road of Shijiazhuang City was -0.23-0.37. The high values of UTFVI represent the urban construction land, while the low values of UTFVI represent the water bodies and green spaces. The average surface temperature of Minxin River was 35.82℃, and its average UTFVI was lower than 0.02, leading to a strip-shaped " cold zone" in the urban region with high-temperature area. (2) The average cooling distance across the Minxin River was 165 m. Within the buffer zone on both sides of the river, the average surface temperature raised rapidly with the increasing buffer distance and then basically remained unchanged. (3) The average UTFVI values in the whole region of Minxin River were lower than 0.05. The cooling effect of east line of Minxin River was the best, the cooling distance reached to 210 m, and the cooling amplitude was 1.59℃. The cooling effect of the second Minxin River is the worst, and the cooling distance was only 60 m, and the cooling amplitude was about 0.19℃. The cooling distances of the west, south, north and middle lines of Minxin River were 150, 120, 180 and 270 m, respectively, and the corrsponding cooling amplitudes were 0.65, 0.40, 1.60 and 1.39℃, respectively. (4) Within 60 m of the minimum cooling distance of the Minxin River, a cold island effect occured when the proportion of green space was higher than 50%, the proportion of urban construction land was lower than 48%, and the average UTFVI of the urban water body was lower than zero. At that time, the comprehensive cooling effect of green space and the Minxin River was the largest. The research will provide guidance for construction of urban artificial rivers and the rational layout of shoreside landscape structures.