Journal of Civil Engineering Research 2014, 4(3A): 233-236 DOI: 10.5923/c.jce.201402.40 Drainage Systems for Flood Control in Medan Selayang, Indonesia, Based on Rainfall Intensity and Drainage Evaluation Rumilla Harahap 1,* , Kemala Jeumpa 2 , Bambang Hadibroto 3 Universitas Negeri Medan, Medan, Indonesia Abstract One of the causes of drainage conditions in some places does not work anymore is due to the smaller capacity of the existing discharge, lack of care or the drainage systems and disposal that is no longer compatible with the environment, thus resulting in flooded every year. This study aim to investigate the intensity of the rain and drainage capacity in the city of Medan, North Sumatra, especially Medan Selayang area, to evaluate the regulation of drainage system in Medan city in order to reduce excess water. The evaluation of drainage in the analysis through the Rasional method. The results shows that the peak of flood discharge obtained in the catchment area of the drainage network system for 10 year return period is 29.697 m 3 /s. Keywords Medan Selayang, Drainage system, Rational Method 1. Introduction Physically city of Medan region shows a relatively small height difference, surplus water from upstream areas greater than downstream areas, the ability of the soil to absorb water into the city has decreased because of the less open land [1]. The changes in land use becomes vacant housing will increase the flow of water through drainage systems and rivers [2], also the flood due to changes in weather/climate contributed significantly contribute to flooding the city of Medan. The goal of this research is to analyze and evaluate the intensity of the rain drainage channels in the city of Medan and to predict technically the periodic flood discharge using the Rational method as a reference in the drainage discharge. 2. Literature Study Each activity is involving objects, such as housing, offices, and industries must consider the flow of rain water. Each activity is involving objects, such as housing, offices, and industries must consider the flow of rain water. The development of land is usually followed by the addition of water-resistant coating that results in an increase in the rate * Corresponding author: rumi_harahap@yahoo.com (Rumilla Harahap) Published online at http://journal.sapub.org/jce Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved and volume of runoff. Hydrological analysis is a field that is very complicated and complex. This is due to uncertainty in hydrology, the limitations of the theory and data recording, as well as economic limitations. The rain is unpredictable events. That is, we can not predict with certainty how much rain will occur over a period of time. 2.1. Hydrology Analysis Understanding of hydrological processes important in the conservation of water and soil to determine between water availability and water demand in the surrounding watershed to the sea. hydrological cycle [3]. Inside the a watershed, natural resource characteristics can be identified in detail with regard to topography, soil, geology, geomorphology, vegetation, land use, hydrology and human. As known characteristics of the watershed such as Fig.1, you will get a general overview of the nature and condition of drainage characteristics that are useful for the preparation and analysis of drainage. 2.2. Frequency Analysis Frequency analysis is the procedure of estimating the frequency of an event in the past or future. The procedure can be used determine the design rainfall in different time based on the theoretical distribution of rainfall with rainfall distribution empirically. Rain this design is used to determine the intensity of rain is required in estimating the peak flow rate (flood discharge).