Development of rainfall hyetographs for the North Coastal Area of Central Java

Abstract Temporal distribution of hyetograph is a significant data used by engineers for designing hydraulic structures and urban drainage systems. It is used to estimate peak flood discharge and flood volume. The design storm hyetograph need to be determined accurately before taking any hydrologic analyses. The North Coast of Central Java-Indonesia has been severely affected by flooding during the last two decades. So far, engineers have predicted flood discharge using hyetographs from elsewhere, even though the storm’s characteristics are local. The developed hyetograph in a certain region may not necessarily be adopted in different places. Therefore, it is necessary to develop local hyetographs. This article is aimed to develop hyetographs for the North Coast of Central Java-Indonesia. Analytical statistic approach to historical data is applied to develop the storm hyetographs. The results reveal that there was a difference between the Alternating Block Method (ABM) hyetograph, which tended to be symmetrical, and the hyetograph developed tended to skew to the left (positive skewness), with lower peak storm. It is recommended to evaluate the use of the ABM method in other locations in Indonesia by developing hyetographs based on historical rainfall data.