Abstract
Development of Intensity-Duration-Frequency (IDF) Curves is important for the design of various hydraulic structures such as culverts, dams, and stormwater drainage systems. In this paper, rainfall analyses are conducted to evaluate the effect of using rainfall records from different rain gauge types on IDF Curves construction. Rainfall data are collected from two recording rain gauges at Namman catchment in western Saudi Arabia. Using the available 13 years rainfall data of the two gauges, annual maxima rainfall series values are extracted and used for IDF curves computations. The rainfall gauge which is equipped with a siphon produced IDF curves with higher precipitation intensities in comparison with the other gauge. This indicates that the siphon mechanism plays an important role in decreasing the under-catchment amount of the tipping bucket gauges during heavy rainfall storms. The current study shows that the under-catchment amount of tipping-bucket rain gauges can have a significant impact on the IDF curves and the characteristics of the design storm. A correction relationship to adjust rain intensity data sets of recording rain gauges that are not furnished with siphons is proposed in this paper. The adjusted rainfall intensity values are utilized to construct reliable IDF curves.