Computational Engineering and Physical Modeling 3-3 (2020) 01-11 How to cite this article: Romero R, Romero N, Romero F, Cronico JC. Assessing Flood Occurrence and Modeling Impact of Urban Drainage Structure. Comput Eng Phys Model 2020;3(3):1–11. https://doi.org/10.22115/cepm.2020.221035.1090 2588-6959/ © 2020 The Authors. Published by Pouyan Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Contents lists available at CEPM Computational Engineering and Physical Modeling Journal homepage: www.jcepm.com Assessing Flood Occurrence and Modeling Impact of Urban Drainage Structure R.V. Romero * , N.V. Romero , F.B. Romero , J.C. Cronico Partido State University, Goa, Camarines Sur, Philippines Corresponding author: munding25@yahoo.com.ph https://doi.org/10.22115/CEPM.2020.221035.1090 ARTICLE INFO ABSTRACT Article history: Received: 23 February 2020 Revised: 10 April 2020 Accepted: 10 April 2020 This study evaluated the catchment and flood prone area by applying physical and numerical modeling. This described rainfall data and presented evidences of flooding based from extreme precipitation events. Mathematical models were derived using the definition of discharge and Manning’s formula which finally were used to estimate the sufficiency of the river canal cross sectional area to transport great amount of water flow. Mt. Isarog, mountain ranges of Lagonoy and the low land area are the sources of flood water in Lagonoy River. The amount of daily precipitation is always insufficient to induce flooding except for a terrifying event that the area was heavily affected. The river canal cross sectional area is sufficient to accommodate flood water flow but the position of the moon which is indicating differences on river depth during full/new moon and first/third quartermoon, high tide and low tide, and with heavy and non-heavy rainfall.causes the flood while others are due to river bends, insufficient design of spillway and obstruction of irrigation waterway. Keywords: Flood; Drainage structure; Modeling impact; Extreme precipitation. 1. Introduction Climate in the Philippines is influenced by complex interaction of various factors such as geography and topography. More extreme weather events are coming with more people affected by typhoon related hazards. Duration and intensity of rainfall events have changed