Investigation of the Effect of River-Valleys on the Surrounding Thermal Condition on a Micro-climate Scale; Case Study: Darakeh River-Valley, Tehran

Natural structures in a city guarantee ecological quality and have serious impacts on urban issues like urban development, urban climate and etc. one of most important structures in Tehran are the river-valleys, which in recent decades due to unbalanced urban developments, some are in unpleasant conditions. Simultaneously, Tehran has faced various climatic problems, air pollution and relevant consequences, which can be partly due to urban ecosystems deteriorations. Therefore, this study intends to examine the relationship between river-valleys and their surrounding micro-climate through literature review and then, as a case study, this is examined in Darakeh River-Valley by simulating and analyzing its micro-climate using ENVI-met model. During this process, the influence of climatic elements such as waterbodies, vegetation, valley configuration (Topography) and airflow is evaluated by parameters such as Potential Air Temperature, Mean Radiant Temperature, Wind Speed and Relative Humidity. The simulation results show a limited cooling effect of waterbodies (Due to lack of required extent), cooling of surrounding air up to 0.5 degrees by vegetation. Furthermore, parameters such as Relative Humidity due to correlation with wind speed, air temperature and solar radiation (up to 6%); Mean Radiant Temperature with exposure condition to solar radiation as-well-as surface temperature, regarding vegetation and its shading (Up to 22.5 degrees); and Wind Speed with altitude and obstructive role of vegetation and valley configuration (Topography) (Up to 2 m/s) are variable, but the range of potential air temperature variation is low as heat exchanges between site points over whole site area (Up to 2 degrees).