Perhitungan debit banjir rencana merupakan suatu bagian yang sangat penting dalam merencanakan bangunan air. Dengan perencanaan debit banjir yang tepat dan sesuai akan menyebabkan pembangunan sarana prasarana keairan menjadi efektif dan efisien serta dapat mengurangi resiko akan kegagalan bangunan akibat bencana alam seperti banjir. Selain pemilihan periode ulang rencana yang tepat sesuai dengan resiko yang akan dihadapi oleh suatu bangunan keairan, dalam perhitungan debit banjir rencana juga diperlukan metode yang tepat untuk dapat menggambarkan hidrograf yang sesuai dengan karakteristik suatu daerah aliran sungai (DAS) dimana suatu bangunan keairan tersebut akan dibangun. Sub DAS Konto, salah satu anak Sungai Brantas, yang merupakan sungai besar dan penting di Jawa Timur. Sehingga keberadaan debit airnya juga sangat menentukan kebermanfaatannya untuk kehidupan masyarakat sekitar. Didalam penelitian akan menggunakan metode Nakayasu dan ITB yang dibandingkan dengan hasil pengukuran debit di lapangan.

This paper presents a numerical modeling to simulate flood inundation and dam break analysis of Way Apu dam for an emergency action plan (EAP), by considering EAP guidelines for ICOLD (International Committee on Large Dam). The Way Apu dam, located in Way Apu River, Maluku, Indonesia is a multi-purpose dam constructed mainly for irrigation, hydropower, water supply, and flood control. Therefore, the dam's outflow discharge needs to be analyzed, due to the large amount of rainfall in eastern Indonesia. Thus, there is a need to analyze flood inundation mapping and dam break simulation in a bid to identify the flood mitigation risk zone and early warning system, within the downstream area of Way Apu dam. In this study, the flood inundation mapping and dam break simulation were analyzed using HEC-RAS 5.0.7. The analysis results of flood routing generate the outflow peak discharge reduction over spillway were 7.36 % (Ten years return period discharge, Q 10 ) and just 2.14% (Probable maximum flood discharge, Q PMF ), indicating the simulation results of Hec-Ras 5.0.7 model for conditions with or without dam break did not show significant difference in dam's downstream area. According to these results, 6 sub-districts are affected by the flood (Grandeng, Waeleman, Wanakarta, Waenetat, Debowae, Mako) with a maximum flood height range between 1-2.5 m (Q 10 ) and 2.9-4.2 m (Q PMF ). The simulation results of arrival time also showed the estimation of evacuation time for Q PMF ranges from 6 -12 hours.

This study presents a flood hydrograph numerical modeling of the Keser watershed for disaster risk mitigation and water resources management for an emergency action plan (EAP) on the Tugu dam. Several formulations for calculating peak discharge, which are associated with information on flood design in Indonesia are regulated in SNI 2415:2016 regarding the procedure of flood discharge calculation and design. This information is important and related to water structure dimensions, risk, costs, and reliability. The complexity of watershed conditions affects the hydrograph shape and volume. Hence, a performance analysis is needed to identify the best current hydrograph model. In this study, the performance of Nakayasu, Gamma 1, and Snyder SUH was analyzed and compared with the numerical modeling using the HEC-RAS 2D hydrodynamics precipitation on grid and HEC-HMS numerical model in the Keser watershed with one-hour rainfall height of 114.92 mm (R50). Based on the calculation results, the hydrologic numerical model flood discharge calculation using HEC-HMS method was 451.1 m 3 /s. The peak discharge values obtained using the Nakayasu, Gamma, and Snyder methods were 424.2, 410.4, and 439.4 m 3 /s, respectively. The results of the numerical model with HEC-RAS 2D v6.3 with uniform precipitation on the grid obtained a peak discharge hydrograph value of 420.98 m 3 /s. Therefore, the highest peak discharge results were obtained from the HEC-HMS method among the three SUH formulas and HEC-RAS calculations. Hence, the deviation of peak discharge value using three SUH, HEC-HMS, and HEC-RAS was obtained under 10%.

This study presents numerical modeling to simulate the rainfall-runoff model using Génie Rural à 4 paramètres Journalier (GR4J) of the Keser Watershed (East Java, Indonesia) to predict the reservoir inflow of the Tugu dam. The four independent parameters used to optimize the daily rainfall-runoff model are the maximum capacity of the production store (X1), the underground water exchange coefficient for the catchment (X2), the one-day capacity of the routing storage (X3), and the time base of the unit hydrograph (X4). The TRMM daily precipitation satellite time series is used as the rainfall input data spanning two years (2017)(2018). Furthermore, the potential evapotranspiration for the catchment was calculated using the Penman method. The rainfall-runoff transformation results of the discharge simulation were then compared with observed discharge data collected from the hydrometry gauge station. The simulation results showed that the best performances of the model obtain 7.85, 2.52, 3.93, and -1.35 for the coefficient result of the maximum capacity of the production store (X1), the underground water exchange coefficient (X2), the one-day capacity of the routing storage (X3), and time base of the unit hydrograph (X4) respectively. In addition, the Nash-Sutcliffe coefficient's deviation value obtains 0.73, which is considered a good performance model (0.65

Padi Pomahan Irrigation Area has a lack of sufficient amount of water at the downstream area in dry season. This problem is caused by some factors such as the exploitation of drinking water, climate change, land use change, and the damage of irrigation channel. The performance of irrigation channel and its facilities compared with the situation nearly 20 years later has never been evaluated and measured due to the limited of the preliminary data. With the area of 4309 hectares managed by two offices (UPT Pugeran and UPT Tangunan), the coordination become more complex to manage the irrigation water in this area. This paper aims to analyze the irrigation performance at tertiary level to measure the performance of six indicators/criterions such as physical infrastructure, plant productivity, personnel organization, operation and maintenance (OM), documentation, and institutional condition of water user associations (P3A / GP3A / IP3A). The results of its performance are expected to obtain the handling priority at the tertiary level in this irrigation system by Indonesian government. The total irrigation performance In Padi Pomahan obtains 61.0%. The result model of AHP (Analytic Hierarchy Process) obtains the result of personnel organization 28.9% (rank 1), plant productivity 20.3% (rank 2), physical infrastructures 16.8% (rank 3), operation and maintenance (OM 14.2% (rank 4), institutional condition of water user associations (P3A / GP3A / IP3A) 10.5% (rank 5) and documentation 9.3% (rank 6). The ARP model obtains CGI value 0.13 and Consistency Ratio (CR) 0.036.