Many people are living in Purwokerto. A new residential area is built as a result of this density. We must consider the significance of drainage canals when developing settlements. One of the settlements is Bukit Sidabowa Asri, located on Jalan Bukit, Karanggede, Sidabowa, Patikraja, Banyumas Regency, Central Java. High rainfalls frequently result in inundation, especially the one that was especially intense in 2012. As a result, it causes road users to experience interference. This study aims to analyze drainage capacity with a rational method in the Bukit Sidabowa Asri housing estate. According to the results of the hydraulics analysis, the drainage capacity that is currently in place can still handle rainwater runoff because the existing Q channel (0.5229144 m/s) is faster than the Q channel from block A (0.0043), block B (0.0011), block C (0.0028), block D (0.0045), block E (0.0027), block F (0.0031), block G (0.0036), block H (0.00401), block I (0.0028), block J (0.0054), until block K (0.0049), (0.0012). Due to several damaged road conditions brought on by the landfill project for the second phase of development in the Sidabowa Asri hill housing, which was related to the occurrence of inundation at the time, rainwater may not have been able to flow properly and maximally due to the amount of clogged garbage.