Flood Hazard Levels Research Articles

Evaluation of Social Vulnerability to Flood Hazard in Basilicata Region (Southern Italy)

Floods are the most common natural hazards causing damage to properties and loss of life worldwide. They are not preventable but vulnerability assessments, hazard mitigation, and effective emergency management plans can reduce their impacts and facilitate recovery actions. Floods can have different impacts depending on the local physical conditions and on the social context represented by the economic and cultural patterns of a specific community. Social vulnerability is the susceptibility of social groups to the adverse impacts of natural hazards, including disproportionate death, injury, loss, or disruption of livelihood. Therefore, the social vulnerability analysis becomes of primary importance in understanding the main factors influencing the capacity of a specific community to anticipate, cope with, and recover from a flood event. In this context, this paper investigates the correlation between flood hazard and socio-economic factors across the Basilicata Region (southern Italy). The aim of this research is to evaluate flood hazard and social vulnerability index through a Geographic Information System (GIS) approach. Multivariate factor analysis was applied in this work to construct an overall social vulnerability index which was combined with the flood hazard distribution. Our results underline the presence of 107,587 people with a high level of both flood hazard and social vulnerability.

ANALISIS SPASIAL DAERAH RAWAN BANJIR DI DAS WAE HERU, KOTA AMBON

The intensity of the high rainfall resulted in the overflow of the Wae Heru watershed, which resulted in a catastrophic flood that hit residential areas around the watershed. This study aimed to analyze spatially the level of flood hazard and its exposure to settlements in the Wae Heru watershed, Ambon City. This research used overlay technique, scoring method and weighting using ArcMap 10.8 software as a Geographic Information System (GIS) based approach. The variables used included rainfall, elevation, slope, soil type, land cover and distance from the river. The results showed that the flood hazard level was dominated by a low hazard level of 361.28 ha and the flood exposure level in settlements was dominated by a high hazard area of 54.68 ha. The results of the study are expected to be useful in flood mitigation efforts to minimize losses, both fatalities and physical damage.

Aplikasi Sistem Informasi Geografis Dalam Pemetaan Zonasi Rawan Banjir Kecamatan Monano Kabupaten Gorontalo Utara

Monano Subdistrict is one of the sub-districts located in Gorontalo UtaraRegency, Gorontalo Province, which does not have a flood hazard map. Thisstudy aims to determine the geological conditions and create a flood hazardmap. This study collected field data, such as lithological data, plotting dataon flood coordinates of each village, as well as validation data of the floodhazard level. The spatial analysis used in this research scores on flood-proneparameters, such as slope, rainfall, and land use that are overlayed alongwith lithological data. As a result, four geomorphological units are obtained:volcanic hills, denudational hilss, and fluvial and marine plains. From thegeological aspect, four units of lithology constituents are produced, such asandesite units, agglomerate units, sandstone units, and alluvial deposit units.The data also exposes that: slopes range from 0-45o flat to very steep, landuse is covered by settlements, rice fields, shrubs, and forests, as well asrainfall which refers to a very high intensity of rainfall, which is 2771 mmper year. The data obtained produces a flood hazard map divided into threeclasses: low, medium, and high.

Evaluation of Flood Hazard Potency in Jakarta based on Multi-criteria Analysis

The frequency of flood events in Indonesia has increased since 1990, especially in the capital city of Jakarta. Flood events have affected socio-economic activities, and have threaten community health in flood prone areas. Although many efforts have been performed to reduced flood impacts, research on flood hazard remains a research challenge. This study aims to map level of flood hazard in Jakarta and to determine the most affected factors that cause flood. First, we defined factors that influence flood, and combined an analytical hierarchy process (AHP) to determine their weighted values and GIS approach to determine their score values. The combination of weight and score value determined the flood hazard index (FHI). The sensitivity analysis and validation then were applied to determine the robustness of the approaches. Our results show that the most influenced factors determining flood hazard were rainfall intensity, land use, and slope, whereas geology is the less factor. Based on the sensitivity analysis and FHI validation, our approaches were able to represent 59% flood disaster in Jakarta. The pattern of FHI value was high in north areas and low in south areas. The findings indicated that north areas are more flood prone than south areas. Further, this research contributes to the improved approach of flood mitigation in Jakarta

Performance Degradation of Levee-Protected Electric Power Network Due to Flooding in a Changing Climate

This paper presents a methodological framework to evaluate the resilience, with the primary focus on performance degradation, of levee-protected electric power networks to flooding in a changing climate. To this end, a multi-disciplinary framework is established by integrating climate science, hydrology, and electric power network analysis. The framework quantifies the effect of climate change on flood hazard levels in a levee-protected area and the subsequent changes in the resilience of the electric power network. In the first step, the changes in the exposure of levee-protected regions to flooding hazard in a warming climate are calculated. Then, the probabilities of failure of power network components due to flooding under current and projected future climate are determined. Finally, the power system resilience index is used to assess the system resiliency for pre-flooding (baseline), historic flooding, and two projected future flooding scenarios. For demonstration, the proposed framework is applied to a levee-protected area in Northern California. The IEEE 118-bus standard test system is employed to represent the power network in the study area. Results reveal that climate change can considerably decrease the system resilience of the levee-protected electric power network. The findings of this study can contribute towards more resilient power network systems under a changing climate.

Land Use Planning to Reduce Flood Risk: Opportunities, Challenges and Uncertainties in Developing Countries.

Land use planning for flood risk reduction has been significantly addressed in literature. However, a clear methodology for flood mitigation oriented land-use planning and its implementation, particularly in developing countries like Lebanon, is still missing. Knowledge on land use planning is still in its earliest stages in Lebanon. A lack of hazard-informed land use planning coupled to random land cover pattern evolution characterize the country. In response, this study focuses on the opportunities, challenges and uncertainties resulting from the integration of land use planning into efficient Disaster Risk Reduction (DRR). For this purpose, GIS-based analyses were first conducted on the current land use/land cover (LU/LC) of the Assi floodplain. Then, the areas land cover was retraced and its evolution after several flood occurrences was assessed. Subsequently, a flood hazard-informed LU/LC plan was proposed. The latter is mainly based on the spatial allocation of land-uses with respect to different flood hazard levels. This approach resulted in the production of a land use planning matrix for flood risk reduction. The matrix approach can serve as a tool for designing sustainable and resilient land cover patterns in other similar contexts while simultaneously providing robust contributions to decision-making and risk communication.

Analysis of Distribution of Flood Disaster Hazard in Tangerang City

Tangerang City was largest city in Banten Province with total area of 184.23 km2. Tangerang City was generally combination of coastal areas with lowlands condition which is located along Cisadane River. Mapping of flood-prone areas in Tangerang City aims to identify areas which have potential for flooding, so these areas can be analyzed for preventing action. In this research, flood-prone areas were identified using scoring method. The flood parameters consist of land height, slope, rainfall, soil type, land cover, and river range. Spatial information was represented in form of map, while attributes of spatial information were represented in tabular form using different parameters and weight values in mapping flood hazard in Tangerang City. The results show us that level of flood hazard in Tangerang City was divided into four classes of hazard, namely level of flood hazard “safe” in Benda District with area of 0,831 Ha, level of flood hazard “slightly vulnerable” in Jatiuwung District with area of 155,897 Ha, level of flood hazard “Prone” occur in Pinang District, which has area of 1.360,161 Ha, while level of flood hazard “very vulnerable” was in Benda District, which has area of 1.358,454 Ha.

Geospatial technology for flood hazard analysis in Comal Watershed, Central Java, Indonesia

River flood has become a severe disruption toward the community, and it can trigger loss of life, damage infrastructure and properties, suffer economic, social and cultural, and environmental degradation. Flood hazard analysis downstream of Comal Watershed in Pemalang Regency, Central Java, was designed to generate the flood hazard map to reduce the effects of flood disaster. The flood hazard was simulated for five, 10, 25, and 50 years using HEC-RAS and ArcGIS with HEC-GeoRAS. The data input was discharge, geometry, and roughness. The discharge was obtained from hydrology modelling by utilizing daily rainfall data for 22 years. The geometry data was composed of a topographic map and measured using an echo sounder, while the roughness was from land use along the flood plain. The accuracy and validation were conducted by matching the flood modelling result with the historical data from the Pemalang Disaster Management Agency and in-depth interview results with the community. The results showed the Comal River downstream flood hazard was feasible for disaster risk reduction purposes. The flood hazard levels were generated in five, 10, 25, and 50 years return periods dominated by high and very low levels. In every return period, the rising trend of the inundation width and the flood depth occurred for very high, high, and very low levels.

Flood hazard and susceptibility assessment in a semi-arid environment: A case study of Seyad basin, south of Morocco

Flood, is a constant phenomenon, especially in semi-arid and flood plain regions are one of the most destructive natural hazards endangering a people's life, property, and physical and economic well-being. This paper focuses on hydraulic modelling using the HEC-RAS model in combination with the Watershed Modeling System (WMS) tools and compares the results to the Flood Hazard Index (FHI) method using GIS in the Seyad Basin situated in the southwestern region of Morocco with an area of 1512.85 km2. The goal of the study is to evaluate flood hazards in the Seyad Basin in which the cities of Taghjijt, Aday, Amtoudi, and Tagriante are located. The HEC-RAS approach combines the hydraulic surface water flow model and the digital terrain model data. This combination allows the mapping of the flood zones by using the WMS tools. This approach predicts flood occurrence probability for different times and determines the intensity of the flood (depth and velocity of floodwater) using the existing hydrological data.On the other hand, the Flood Hazard Index method (FHI) presents a multi-criteria index to assess areas prone to flood hazards, using six physical parameters: permeability, slope, distance from rivers, land use, drainage density, and flow accumulation. A weight is calculated from the analytic hierarchy process method and applied to each parameter. HEC-RAS method allows the mapping of a flood with a flood water surface profile that shows the flood depth for Annual Exceedance Probability (AEP). At the same time, FHI permits establishing flood hazard levels without showing the water depth. In both approaches, six simulations were performed with the return periods of 10, 20, 50, 100, 200, and 500 years. The simulation revealed that the most susceptible areas to flooding are the areas along the Wadi Seyad.

Flood hazard mapping of the Welang river, Pasuruan, East Java, Indonesia

The availability of a flood hazard map is beneficial during flood risk reduction. However, there is a lack of high-resolution topographic data, which is a map realization obstacle. Therefore, this study aims to construct flood hazard maps based on hazard levels for various flood return periods. The 2D-hydrodynamic from the Hydrologic Engineering Center's River Analysis System (HEC-RAS) and Digital Surface Models (DSM) from Unmanned Aerial Vehicle (UAV) imagery were used for generating inundation maps. The results showed that simulation of return periods for 2 and 10 years illustrated a 37% increase in flood hazard levels. Furthermore, there was an increased danger level for locations that were exposed to flood inundation. This occurred in housing, some roads, and rice fields. Ultimately, this study mitigates flood hazards through the determination of evacuation directions, urban spatial planning, and informed flood mitigation measures.

An Extended Watershed-Based AHP Model for Flood Hazard Estimation: Constraining Runoff Converging Indicators via MFD-Derived Sub-Watershed by Maximum Zonal Statistical Method

Floods threaten the sustainable development of areas with a high probability of hazard. A typical analytic hierarchy process (pixel-based AHP) based flood hazard estimation method may ignore the similar threat caused by neighborhood cells at the sub-watershed scale. This study proposed an extended watershed-based Zonal Statistical AHP for flood hazard estimation: Constraining converging related indicators by the sub-watersheds (WZSAHP-RC) model to improve this gap. Before calculating the flood hazard index, the proposed model uses the sub-watershed derived by the multiple flow direction method as a based unit to calculate the maximum zonal statistical value of runoff converging indicators. Moreover, taking the Chaohu basin of Anhui in China as the case study, the validation flooding ground-truthing was constructed from GF-3, and Landsat OLI images of the flood event from 20 July to 24 July 2020, which is the biggest flood recorded by the Zhongmiao station, which recorded a new water level, 0.82 m higher than the historical record. Compared with the validation, the results indicated the proposed method could improve the correct ratio by 38% (from 22% to 60%) and the fit ratio by 17% (from 18% to 35%) when considering the predicted flood hazard levels of “High” and “Very High” as flooded areas. Moreover, the flood hazard map derived by WZSAHP-RC demonstrated greater consistency in the flooded districts filtered by Baidu News than the pixel-based AHP. It revealed that considering two- or even multi-dimensional homogeneity may help to improve the accuracy of flood hazard maps on a catchment scale.

ANALYSIS OF FLOOD DISASTER AREAS, JOMBANG REGENCY, EAST JAVA USING ARCGIS REMOTE SENSING

Flood is one of the natural disasters that occur in Indonesia. Each region in Indonesia has a different flood hazard level. Therefore, a study was conducted to map the level of flood hazard in Jombang Regency, East Java. Remote sensing methods are used to map flood-prone areas, ArcMap software is used to map disaster-prone areas and mapping vegetation density. The data required is in the form of flood data index from Inarisk and Landsat 8 imagery data from USGS. From these data, four maps were generated, namely the vegetation density map and the flood hazard map in the Jombang area. From the vegetation density map, it can be seen from the value it determines the level of vegetation density in the area, while the flood hazard map is categorized into three hazard categories, namely low, medium and high. And it was found that the lower the level of vegetation density, the higher the level of flood hazard in the area, and vice versa and it is also known that the Brantas river affects flooding in Jombang. Then seen from the regional geology, the area of North Jombang absorbs air more quickly because it is composed of karst rocks. Judging from the area of the flood hazard level, the Jombang area is more dominant to the moderate hazard level.

Strategy to improve regional resilience against flood disasters in the North Coast of Central Java

The impact of climate change has caused flooding in the North Coast of Central Java Province. The level of flood hazard in 14 urban/municipalities on the North Coast of Central Java is all in the high category. The potential population exposed to flooding in this area reaches around 11,589,000 people, where a third are vulnerable groups (the poor). The impact of the flood disaster has caused environmental damage as well as physical and economic losses. This article aims to examine strategies to increase the resilience of the North Coast of Central Java using the Socio-Ecological System (SES) approach, where there is a reciprocal relationship between aspects of nature/environment (Natural System) and socio-economic (Socio-Economic Systems). Given that vulnerability (V) in the Pantura area of Central Java is dominated by many poor people and vulnerable groups, the strategy that needs to be done to reduce vulnerability is through poverty alleviation programs. To reduce the level of exposure (E) in the form of large physical and economic losses, it is necessary to provide the urban infrastructure that ensures the sustainability of the socio-economic activity system can take place properly. In addition, it is also necessary to control land use change because this has reduced the capacity and storage capacity of water, as well as prevented flooding. Finally, to overcome environmental damage, it is necessary to carry out an environmental conservation program on the North Coast of Central Java in a comprehensive and sustainable manner.

Probabilistic Flood Hazard Mapping Considering Multiple Levee Breaches

AbstractProbabilistic methods are widely adopted for residual flood hazard assessment in flood‐prone areas protected by levees. Such methods can consider various sources of uncertainty, including breach location and flood event characteristics, and allow for the quantification of the result confidence. However, the possible occurrence of multiple levee breaches during the same flood event is usually disregarded. This paper presents a probabilistic method based on levee fragility functions and basic probability rules to estimate the probability of selected breach scenarios, including multiple breaching events. The flood hazard classification is based on inundation variables calculated for flood events of different return periods. A combined 1D‐2D hydrodynamic model is used for flood simulations. Probabilistic inundation extent maps and probabilistic flood hazard level maps are then created. Finally, probabilistic flood hazard estimates are summarized in a map of a suitable central tendency of the hazard level, coupled with a map of the Shannon entropy as an uncertainty indicator. This pair of statistical maps provides concise and effective information on a reference flood hazard along with the associated uncertainty. The method was applied to a region located along the middle reach of the Po River (northern Italy). Comparable central flood hazard estimates are obtained for the two sets of breaching events including or not including multiple breaches, with higher uncertainty if multiple breaches are considered. This result highlights the importance of considering multiple breaching events in flood risk management.

Flood Hazard and Risk Mapping by Applying an Explainable Machine Learning Framework Using Satellite Imagery and GIS Data

Flooding is one of the most destructive natural phenomena that happen worldwide, leading to the damage of property and infrastructure or even the loss of lives. The escalation in the intensity and number of flooding events as a result of the combination of climate change and anthropogenic factors motivates the need to adopt real-time solutions for mapping flood hazards and risks. In this study, a methodological framework is proposed that enables the assessment of flood hazard and risk levels of severity dynamically by fusing optical remote sensing (Sentinel-1) and GIS-based data from the region of the Trieste, Monfalcone and Muggia Municipalities. Explainable machine learning techniques were utilised, aiming to interpret the results for the assessment of flood hazard. The flood inventory was randomly divided into 70%, used for training, and 30%, employed for testing. Various combinations of the models were evaluated for the assessment of flood hazard. The results revealed that the Random Forest model achieved the highest F1-score (approx. 0.99), among others utilised for generating flood hazard maps. Furthermore, the estimation of the flood risk was achieved by a combination of a rule-based approach to estimate the exposure and vulnerability with the dynamic assessment of flood hazard.

Assasment of flood hazard reduction in DKI Jakarta: Bendungan Hilir Village

Jakarta has an essential function for Indonesia, apart from being the capital city of the country, Jakarta is also the center of the nation’s economy. However, the problem of flooding that occurs every year causes enormous material and immaterial losses. One of the metropolitan areas that is often hit by floods is Bendungan Hilir Village. This village is the meeting point between the Ciliwung River and the Krukut River. One of the causes of flooding is when the water level in both rivers is high, the water from the Krukut River cannot flow, so it overflows into the surrounding area. For this reason, this study will analyze the level of flood hazard and the effect of normalization of the Krukut River. The analysis was performed using the HEC-RAS, combining 1D and 2D modeling. In the upstream part, the Krukut watershed flood hydrograph is applied for a return period of 25 years with a peak discharge of 169 m3/s, and the normal depth will be used as the downstream boundary. The modeling is carried out in two conditions, they are the existing channel and the channel after normalization. Based on the model results it is found that normalization could reduce the flood hazard of Krukut river around 75%.

ANALYSIS OF FLOOD HAZARDS IN MAGETAN REGENCY USINGDISTANCE SENSING METHOD

Flood is an annual disaster that hits all over Indonesia, and Magetan Regency is one of the affected area . The high regional topography in the western part and the relatively flat topography in the eastern part making it potential for flood to be higher in the eastern part. The DEM (Digital Elevation Model) topography, Landsat maps, and hazard index maps can be identified by remote sensing using regional administration map data, the level of slope slope and vegetation density can be mapped using NDVI method, and the classification of the flood risk level of an area can be done using ArcGIS software. The slope of the slope and the density of vegetation will affect the level of potential flood hazard. There is a low level of potential for flooding on steep slopes because the air will flow and accumulate on the lower plains. Higher vegetation density will provide a good air catchment area. The level of vegetation density is also higher in the western part. Based on the percentage of the affected area, the low flood hazard level reaches 73.3%, so it can be concluded that the flood hazard level in Magetan Regency is low. It is necessary to provide adequate land and channels capable of providing air flow.

Integration of GIS-Based Multicriteria Decision Analysis and Analytic Hierarchy Process for Flood-Hazard Assessment in the Megalo Rema River Catchment (East Attica, Greece)

This study deals with the flood-hazard assessment and mapping in the catchment of Megalo Rema (East Attica, Greece). Flood-hazard zones were identified utilizing Multi-Criteria Decision Analysis (MCDA) integrated with Geographic Information System (GIS). Five factors were considered as the most influential parameters for the water course when high storm-water runoff exceeds drainage system capacity and were taken into account. These factors include slope, elevation, distance from stream channels, geological formations in terms of their hydro-lithological behavior and land cover. To obtain the final weights for each factor, rules of the Analytic Hierarchy Process (AHP) were applied. The final flood-hazard assessment and mapping of the study area were produced through Weighted Linear Combination (WLC) procedures. The final map showed that approximately 26.3 km2, which corresponds to 22.7% of the total area of the catchment, belongs to the high flood risk zone, while approximately 25 km2, corresponding to ~15% of the catchment, is of very high flood risk. The highly and very highly prone to flooding areas are located mostly at the southern and western parts of the catchment. Furthermore, the areas on both sides of the channel along the lower reaches of the main stream are of high and very high risk. The highly and very highly prone to flooding areas are relatively low-lying, gently sloping and extensively urbanized, and host the densely populated settlements of Rafina-Pikermi, Penteli, Pallini, Peania, Spata, Glika Nera, Gerakas and Anthousa. The accuracy of the flood-hazard map was verified by correlating flood events of the last 30 years, the Hydrologic Engineering Center’s River Analysis System (HEC–RAS) simulation and quantitative geomorphological analysis with the flood-hazard level. The results of our approach provide decision makers with important information for land-use planning at a regional scale, determining safe and unsafe areas for urban development.

Flood Rate Assessment of the Woyla River Watershed, Aceh Province, Indonesia

This study aims to assess Flood susceptibility and flood hazard levels and obtain the distribution of hazard levels and flood hazards in the Woyla watershed, Aceh Province. This research design generally uses a descriptive survey method and divide into several stages, such as data collection, data processing, data presentation, and delivery of research results. Each determinant of flood-prone areas includes a land slope, altitude, soil texture, drainage, land cover, and rainfall, analyzed spatially utilizing a map. Furthermore, based on the map, the regions are described based on the values that have been divided into classes. The results showed that the level of flood vulnerability in the Woyla watershed was divided into five classes, namely; the non-vulnerable class with an area of 14.88 Ha / 0.01%, low prone with an area of 90,731.62 Ha / 35.45%, medium with an area of 57,120.35 Ha / 22.32%, high with an area of 44,918.15 Ha / 17.55%, and very high with an area of 63,151.72 Ha / 24.67%. Also obtained a map of the distribution of flood hazard areas, the Woyla watershed area is divided into five classes, namely; the very light class with an area of 179,146.15 Ha / 70.00%, mild with an area of 32,868.84 Ha / 12.84%, moderate with an area of 20,129.93 Ha / 7.87%, danger with an area of 6.007. 29 Ha / 2, 35%, and very dangerous with an area of 17,784.51 Ha / 6.95%. The level of flood vulnerability in the Woyla watershed is dominant in West Aceh Regency, which is in the very high and high category classes with a total area of 56,876.65 Ha and 23,527.40 Ha. Meanwhile, the level of flood hazard in the Woyla watershed is also more dominant in West Aceh Regency than falls into the most dangerous and dangerous class category with a total area of 17,784.51 Ha and 6,007.29 Ha. With the largest part in the very light class at the flood hazard level of 179,146.15 ha.

APPLICATION GIS AND REMOTE SENSINGTO ESTABLISH FLASH FLOOD HAZARD MAP IN TUYEN QUANG PROVINCE

Tuyen Quang is one of the provinces at high risk of flash floods in the Northern Midlands and Mountains of Vietnam. In the rainy season, like other localities in the region, Tuyen Quang has a long, concentrated rainfall combined with steep hills and mountains, large divisions, many rivers, and streams; In addition, the thinning of the vegetation cover due to excessive exploitation of the forest by the local people causes flash floods to appear more and more. Applying GIS and remote sensing to establish a map of flash flood risk is a quantitative approach and high reliability. This article has established a flash flood hazard map at a scale of 1/100,000 in Tuyen Quang province. In the map database, districts with a high risk of flash flood were identified, including Na Hang, Chiem Hoa, Ham Yen, and Lam Binh, the average flash flood hazard level included districts: Yen Son, Son Duong; Tuyen Quang city has a low risk of flash floods.