Reduce Flood Losses Of Kali Tanggul Using Spatial Based Technical Approaches

Flood disasters frequently occurred in Jember Regency, East Java. It is usually caused by the overflow of the Tanggul River in the rainy season, especially in the downstream area. Flood control could be done by building dams, embankments, shortcuts, and other technical flood protections. Meanwhile, mitigation efforts such as developing thematic maps of flood inundation need to be done to minimize losses caused by the flood. This study aims to design a flood mitigation strategy technically. The flood control structure was proposed by designing a shortcut in Kali Tanggul. Its performance was analyzed to reduce flood inundation in the Tanggul watershed. The flood inundation modeling was carried out using spatial analysis using ArcGIS 10.1 and hydraulic analysis using HECRAS 5.0.3. Flood inundation results were compared with the Tanggul watershed flood map developed by UPT PUSDA Lumajang. Based on modeling results, flood control using shortcuts is considered an effective strategy for flood mitigation. It was indicated by the reduction of flood inundation distributions, flood inundation height, and flood-affected areas. The results show that the flood height decrease 0.47 up to 0.56 m

Integrating GIS and Analytical Hierarchy Process to Determine Flood Vulnerability Level in Surabaya, Indonesia

Flood is one of the hydrometeorological disasters that occur in Surabaya, especially during the rainy season. The occurrence of floods brings a huge impact on the economy, the environment, and humans’ losses. Based on the National Disaster Management Agency in Indonesia (BNPB) records, the flood inundation height in Surabaya reach about 10 -70 cm for 6 hours. Some anticipation efforts are required to minimize the impact. Therefore, this study aims to provide a flood vulnerability level assessment using the GIS and Analytical Hierarchy Process (AHP) method as a priority recommendation in increasing capacity. This research uses 4 criteria in the assessment including social, economic, physical, and environmental. Each criterion is divided into several classes with adjusted scoring values. The results of the AHP rank the social criteria as the highest weighted value of 0.42322. Furthermore, the results of the flood vulnerability assessment yield some areas that have the highest vulnerability value including Trengilismejoyo District, Wonocolo District, Dukuhpakis District, Sukolilo District, Krembangan District, Semampir District, and Benowo District.

Dam Break Analysis of Gembong Dam Using Zhong Xing HY21

Dams are a form of effort to conserve or protect water resources. The function of the Dam as a reservoir for water, irrigation, power generation, and flood control. However, in addition to its huge benefits, dam construction also can endanger the community’s safety, namely in the form of dam breaks. The main causes of dam break are overtopping and piping. So that analysis is needed related to dam break to minimize the impact. Based on the Zhong Xing HY21 software, the most severe impact of the break of the Gembong Dam was due to overtopping using the QInflow PMF design flood of 724.142 m3/s. It resulted in an inundation area of 54.682 km2 with a maximum inundation height of 5.129 m. As a result of the break of the Gembong Dam, 37 villages downstream of the Gembong Dam were flooded. There are 80.819 people affected by this risk. It is stated that all affected villages are at the 4th hazard classification level or very high hazard.

Kajian Lokasi Rawan Bencana Banjir Pada Daerah Aliran Sungai (DAS) Walanae Kecamatan Dua Boccoe Kabupaten Bone

Bencana Banjir yang sering melanda Kabupaten Bone khususnya Kecamatan Dua Boccoe bukan hal baru. Dalam 20 tahun terakhir, Kecamatan ini sudah identik dengan kawasan banjir yang di sebabkan oleh curah hujan yang tinggi sehingga DAS Walanae meluap. Penelitian yang dilakukan bersifat deskriptif kualitatif atau penelitian terapan. Penelitian kualitatif merupakan penelitian non matematis dengan proses menghasilkan data-data dari hasil temuan berupa Observasi Lapangan. Analisis yang digunakan dalam penelitian yaitu analisis deskriptif kualitatif dengan menggunakan pendekatan Overlay (Superimpose). Dari hasil analisis data diketahui yang sangat berpotensi banjir ada 8 kelurahan/desa, yang meliputi Kelurahan Unyi, Desa Uloe, Desa Pekkasalo, Desa Kampoti, Desa Tocina, Desa Tawaroe, Desa Solo, dan Desa Matajang. Dengan seluas 131 km2, dan tinggi genangan eksisting ± 100-200 cm den periode genangan 10 jam menyebabkan Kecamatan Dua Boccoe sangat berpotensi terkena banjir. Floods is one of disaster that often hit Bone Regency, especially Dua Boccoe Subdistrict. In the last 20 years, flood that happened in this sub-district caused by high rainfall so that the Walanae watershed overflows. The research conducted is descriptive qualitative or applied research. Qualitative research is a non-mathematical research with the process of generating data from the findings in the form of field observations. The analysis used in this research is qualitative descriptive analysis using the Overlay (Superimpose) approach. From the results of data analysis, it is known that there are 8 sub-districts/villages with high potential for flooding, which include Unyi Village, Uloe Village, Pekkasalo Village, Kampoti Village, Tocina Village, Tawaroe Village, Solo Village, and Matajang Village. With an area of 131 km2, and an existing inundation height of ± 100-200 cm with an inundation period of 10 hours, Dua Boccoe District is very potentially affected by flooding

KAJIAN PENANGANAN BANJIR DENGAN SISTEM POMPA DI SUNGAI BENDUNG PALEMBANG

Floods around the Bendung River in Palembang City have caused material and non-material losses. One of the reasons was the decreasing river capacity and backwater during the Musi River flood season, which is the Bendung River's outlet. This paper discusses the impact of adding a pump system to reduce flood impact. 1-dimensional and 2-dimensional numerical model using MIKE 11 and MIKE FLOOD were made to analyze the best measures. Various alternative scenarios were implemented in the model. Based on the modeling results, using the most optimal alternative, alternative 4 with 6 pumps of 36 m3/s and normalization of the Bendung River channel by 1 meter. The inundation area was reduced by 0.74 km2. Also, the maximum inundation height for the flood decreased by 0.6 meters, and the inundation duration was reduced by 8.5 hours. These modeling results can be a reference for managers and policymakers in managing flood events.Keywords: River channel normalization, pump system, numerical model, flood control, Bendung river

Sequential Simulations of Steel Frame Buildings Under Multi-Phase Hazardous Loads During Earthquake and Tsunami

Based on the experience of the 2011 Great East Japan Earthquake and the following tsunami, this study aims to develop effective analytical tools that can comprehensively be applied to buildings under multi-phase hazardous loads such as seismic motion, fluid force, and debris impact. Simulations by two kinds of analytical tools were conducted. First, a structural collapse analysis of a steel frame building under successive applications of varying loads was performed using the ASI (Adaptively Shifted Integration)-Gauss code, which simulates behaviors of structures by simple modeling. The steel frame building model was first excited under an acceleration record observed in Kesennuma-shi during the earthquake, and fluid forces due to a tsunami wave were applied. Then, the collapse behavior of the building was investigated by implementing a sophisticated contact algorithm in the numerical code to express a collision between debris and a building. It became evident that the damage to the building intensifies if a head-on collision occurs under a tsunami flow with a lower inundation height, and the damage to the building becomes larger if sideway collisions occur under a tsunami flow with a higher inundation height and higher velocity. The second simulation was conducted by using the stabilized finite element method based on the volume of fluid method, to estimate a drag coefficient of an actual tsunami evacuation building with openings. The practicability of an estimated wave force using the drag coefficient was confirmed by comparing with the wave force obtained from the fluid analysis. Finally, a sequential structural analysis, with a debris collision phase at the end, was conducted using the ASI-Gauss code to simulate the washout behavior of the building.

Spatial Analysis on Tsunami Predictions in Pandeglang Regency

Pandeglang Regency is an area that has the potentiel to be hit by tsunamis. The plate subduction paths of Indo-Australia and Anak Krakatau Volcano make Pandeglang Regency a region with a high tsunami potential. One step that can be taken to overcome and minimize losses is to do spatial planning to protect it against potential tsunami damage. This research aimed to evaluate the spatial area of Pandeglang Regency based on the identification of potential tsunami hazards. The concept of modelling the tsunami inundation height developed by Berryman and based on Head Regulation No.4 of 2012 of the Indonesian National Board for Disaster Management has been used to identify potential tsunami hazards. The modelling was carried out by calculating the potential distribution of tsunami wave heights in coastal areas. Three scenarios were used to estimate the distribution. The results showed that the first scenario predicted a maximum tsunami height of 7.5 meters above sea level with the furthest tsunami inundation reaching 1,700.12 meters. Second scenario predicted maximum height of 15 meters, with the furthest tsunami inundation reaching 3,384.62 meters. Meanwhile, the last scenario was able to predict a height of 20 meters and showed the furthest tsunami inundation reaching 5.155,11 meters. These results proved that in all scenarios, the widest inundation would occur in Panimbang Regency. This is due to the relatively small variations in roughness and slope of the surface. The same condition also occurs in the last two scenarios, in which Sumur District was the area most ffected. Therefore, the spatial plan of Pandeglang Regency needs to be evaluated and the function of residential area changed to reduce and prevent large losses.

Experimental Study on Dam-Break-Like Tsunami Surge Impacts on Small Balls Climbing on Different Slopes

An experimental study was carried out to investigate the tsunami surge impacts on small balls climbing on different slopes. Dam-break flows were generated in a flume to simulate tsunami surge. The water surface profiles at the sluice gate were observed, the tsunami inundation height and the surge velocity in the flume were measured, and the maximum climbing heights of small balls on different slopes were recorded. Results show that the dam-break speed and the tsunami surge strength increase with increasing reservoir water level. The increasing tsunami inundation height, the decreasing ball density, and the decreasing ball diameter have positive effects on the maximum ball climbing height. Based on the normalized experimental data, equations for estimating the maximum ball climbing heights on different slopes were proposed as functions of the inundation height, the ball diameter, and the ball density. The calculated values from the equation are generally within [Formula: see text]% of the measured values in the experimental ranges.

Study on Applicability of FEMA Formula in Prediction of Impact Load by Tsunami Drifting Vessels on Coastal Zone Structures

In this study, we consider and evaluate the applicability of the FEMA’s formula which is one of the main simple formulas for calculating impact forces through the comparison with our proposed numerical simulation model. We investigated the situation of collision with a thin structure such as a pillar by numerical experiments based on the particle method, in particular, we focus on the case where the drifting speed is fast in targeting the quay of Shimizu Port, Shizuoka prefecture. We compared the results of numerical experiments obtained by detailed simulations with FEMA’s formula and evaluated the applicable range of FEMA s formula for huge vessels. As results, it was suggested that the overestimation was occurred with FEMA’s formula for large vessel using the inundation height and its velocity. FEMA’s formula calculates the impact force of large vessel on the safe side if the drifting vessel speed is used: the condition of added mass coefficient changes the results, but these indicate the safe side in this study. On the other hand, the results of safety sides are fluctuated depending on the height of the action point of force. Therefore, we confirmed that there is a need to examine the height of the impact point when using FEMA’s formula for large vessels.

Spatial Analysis Study on the Flood Impact of WalanaeCenranae River Area in Soppeng Regency South Sulawesi Province

Cabenge River is part of the WalanaeCenranae River area in Soppeng Regency. Annually, the area around the Cabenge River gets the most losses from floods, both in terms of facilities and infrastructures. This study aims to map the areas prone to flood and flood risk, based on the field that gets the most significant impact. This study uses a Geographic Information System (GIS) as a tool and ArcGis Software in determining the level of vulnerability and risk of flooding at the study site. This type of research is a combination of mapping (topographic results) and map analysis. The variables used are DEM (Digital Elevation Model) data and flood volume. The data processing technique used is the GIS-based inundation model approach using inundation height (H) based on a comparison between the volume of water (V) in inundated areas and the volume of water (Q) of flood sources. The results showed that Lilirilau District was in the high hazard class with an area of 100 km2 and had the biggest impact, while in Liliriaja District, the area that was in a high hazard class was 34 km2 and Ganra District was 21 km2.