Research On Precipitation Trend Analysis And Design Storm Of Tianjin City

Global warming and rapid urbanization change the status of hydrological cycle in different degrees, which leads to the increment of storm intensity and frequency of hydrological extreme value and heavy precipitation. Design storm is the basic for drainage system design and other construction designs. Its reliability provides basis for the municipality’s safety. As the continuous development of economy, economic losses induced by the storm water damage are increasing. Under the background of climate change, it is important and necessary to analyze the trend of precipitation and update the design storm, as well as to improve the methodology for design storm.This thesis utilized the 56 years long historical data collected and provided by Tianjin Climate Centre to conduct a trend analysis by employing Mann-Kendall nonparametric Method. It concludes the followings:The annual precipitation is in the trend of decreasing.A few sampling methods and extreme value distributions were adopted to study these history data. A new IDF curve was developed by employing Gauss-Newton method. The following findings were concluded:the existing IDF curve was smaller, than the newly developed one, thus revising the storm intensity formula was suggested; single recurrence period revising IDF curve was suggested; a single return period formula is much more precise than the multiple return period formula, thus the single return period formula should be adopted instead of the general formula; there was little difference between the results evaluated by annual sampling method and revised annual maximum value method. If there was not sufficient storm records, revised annual maximum value method could be considered.The design rainfall distribution for Tianjin city was derivated by Huff rainfall method based on long time historical rainfall data. Rainfall distribution was proposed and the result was more accurate. Area deduction ratio for Tianjin city was developed. The control area of each rain gauge was determined by Thiesson polygon method for total of 28 automatic rain gauges. A computer program was developed for this purpose.