Journal of the Civil Engineering Forum, September 2023, 9(3):329-342 DOI 10.22146/jcef.7087 Available Online at https://jurnal.ugm.ac.id/v3/jcef/issue/archive Coastal and River Embankment Performance at Cengkareng Drain Estuary Under Compound Hazards Conditions Using HEC-RAS 2D Athena Hastomo 1,* , Evi Anggraheni 1 , Adi Prasetyo 2 , Dwita Sutjiningsih 1 , Mochamad Adhiraga Pratama 1 , Atina Umi Kalsum 3 1 Department of Civil and Environmental Engineering, Universitas Indonesia, Depok, INDONESIA 2 Coastal Engineering Agency, Directorate General of Water Resources, INDONESIA 3 Water Resources Engineering, Vrije Universiteit Brussel, BELGIUM *Corresponding author: athena.hastomo@ui.ac.id SUBMITTED 06 March 2023 REVISED 10 May 2023 ACCEPTED 17 June 2023 ABSTRACT Jakarta is prone to pluvial, fluvial, and coastal flooding due to its geographical location and topography. In response to this problem, the Indonesian government has implemented several master plans, including the National Capital Integrated Coastal Development (NCICD). This ongoing program encompasses the construction of coastal and river embankment that stretch all over the coast of Jakarta. Since many coastal areas in Jakarta are residential or industrial, evaluating this performance of embankment has become crucial for effective flood management. The findings of this research can also support the development of other locations where NCICD embankment plan and enhance coastal resilience. Therefore, this research assessed the effectiveness of coastal and river embankment at Cengkareng Drain, a vital floodway in Jakarta, during extreme events that occur simultaneously. To simulate flooding events, two-dimensional HEC-RAS features were used to numerically calculate the area and depth of inundation. The simulation required geometry, terrain, land cover, and unsteady flow data. For the flow boundary conditions, a 100-year design rainfall, HHWL (Highest High-Water Level), and 100-year design wave were considered to represent estuary conditions accurately. The simulation result showed that the maximum water level influenced by these factors was +3.145 mMSL, while the planned embankment top elevation was +3.40 mMSL. Furthermore, without the NCICD embankment, the simulation showed an inundation area of 1212.37 ha, which was reduced to 1111.22 ha after their implementation, leading to a decrease of 101.15 ha. This reduction significantly decreases potential damage to property and infrastructure, particularly in densely populated areas. The simulation also showed a reduction of 86.49 hectares or 66.22% in the inundation area with a depth exceeding 1 meter. These findings demonstrate the effectiveness of embankment in reducing the inundation area without any overtopping incidents. KEYWORDS Flood Management; Estuary Protection; Embankment; Hydrodynamic; HEC-RAS 2D © The Author(s) 2023. This article is distributed under a Creative Commons Attribution-ShareAlike 4.0 International license. 1 INTRODUCTION Jakarta has always experienced significant chal- lenges in terms of flood management due to its di- rect adjacency to the sea. The topography and hy- drological characteristics of the coastal area make it susceptible to three types of flooding, namely pluvial, fluvial, and coastal flooding. In response, the Indonesian government has implemented var- ious master plans since early 1973, in collabo- ration with the Netherlands Engineering Consul- tant (Nedeco), to address flooding issue in Jakarta. Therefore, the most recent and comprehensive flood management master plan is the National Capital Integrated Coastal Development (NCICD) project. The NCICD project entails a series of ini- tiatives to manage flood in Jakarta effectively. It involves the construction of a 36-kilometre-long seawall along the coast of Jakarta, as well as the implementation of river embankment spanning a total length of 100 kilometres. Among the strate- gically planned locations for intervention is estu- ary of Cengkareng Drain. Similar to most of the Jakarta Coast, Cengkareng Drain estuary consists of settlement and industrial areas. Therefore, the damage caused by flooding will result in huge losses. A previous research by Purnama et al. (2015) conducted in Penjaringan Sub-District showed that economic losses from coastal flooding alone ranged from 424 billion to 329