Uncertainty of Optimal Rain Gauge Coastal Region: Case Study Makassar

Abstract

The quality of rainfall data is very important in disaster or hazard analysis and water resource management. However, the accuracy and density of rainfall gauges are increasing, especially if related to the increasing amount of rainfall due to extreme events, such as floods that occurred in Makassar City in 2019. The purpose of this study is to analyze the scenario of optimal rainfall measurement measures in Makassar City. Determination number of the optimal rainfall equipment acquired by calculation of the coefficient of variation or relative standard deviation and error level based on the latest rainfall data in several locations in Makassar City. The results showed that the change of the number of optimal rain gauges varies with the level of error schemes. If the rainfall measurement wants to be improved, the number of rain gauges must be added. Moreover, increasing rainfall accumulation requires an additional rain gauge. By comparing the monthly rainfall data obtained from the rain station in Makassar, it takes 10 rain stations so that the error level is 5%. Nevertheless, using a longer rainfall duration causes the number of the optimal rain gauge to increase. The optimal rain gauge for annual rainfall data at an error level of 5% is 55 units, while if the error level is increased to 10% then 14 units and 6 units for error levels of 15%. Based on the calculation of the relative standard deviation (RSD) from 5 locations that measuring rainfall in Makassar, the biggest city in west coast Sulawesi Island obtained the level of error level is 10%. The scenario with combined among the five existing rain gauges showed that needs to be added to the rainfall gauge between Panaikang or Biring Romang and Sudiang. It is also important to add equipment on-site between Paotere and Barombong.