Impact Of Floods Research Articles

Impact of Floods on the Socio-Economic Conditions of Communities in Sungai Tabuk

High rainfall resulted in flooding in the Sungai Tabuk area. Floods have had a complex impact on the socio-economic conditions of the community. Analysis of the impact of floods is needed to design post-disaster community development strategies. The purpose of this research is to describe the social and economic impacts of floods in Sungai Tabuk. The research method used is qualitative with data collection techniques through observation, interviews, and documentation. The results showed that the impact of flooding on social conditions included: 1) demographic conditions of the population who experienced changes in social structure, 2) decreased health conditions, 3) decreased quality of education, 4) damage to housing, while the impact of flooding on economic conditions included: 1) loss of livelihood, 2) decrease in income, 3) damage to crops and loss of valuable documents.

Influence of flood events on the response of steep and coarse-grained channels to base-level lowering in an arid setting

The Dead Sea level has been undergoing a continuous and rapid lowering, presently ∼ 1.1 m/yr, providing a real time laboratory to examine the response of drainage systems to base level drop. There is a gap of knowledge concerning the impact of floods on the fluvial system in an environment of continuous base level lowering. Such knowledge is of pronounced importance due to the world-wide reduction of natural water recourses caused by human and climate impacts. We relate the effects of flash floods on morphological changes in small, steep and coarse-grained alluvial channels as a response to a rapid base level fall. We studied the steep (7–9 %) David and Qedem channels draining to the Dead Sea by (i) monitoring flow events using depth transducers and (ii) topographic changes by repeat drone-based photogrammetric surveys to quantify fluvio-morphological dynamics, and (iii) analyzed boulder-related bedforms and their distance from the thalweg. Altogether 15 monitored flow events of varying magnitude led to a wide range of fluvio-morphological changes. Considerable erosion occurred as expressed by bank collapse and channel bed incision. Small events displayed incision with morphological changes limited to the downstream reach, while larger events caused morphological changes throughout the entire channel. Substantial deposition at the outlet occurred together with local mechanisms of deposition upstream. The extents of erosion and net volumes of change highly correlated with event peak-discharge and event water volume. Frequent thalweg deflections occurred, some of which were related to the interaction with boulders. Boulder ribs displayed processes of formation/destruction in multiple phases, often occurring in larger events. The examined aspects illustrate the unique dynamics of a continuously unstable fluvial system under a flash-flood hydrological regime and its impact on fan delta incision and sediment transport processes.

Impact of recent floods on river morphology of Upper Krishna River: a decadal analysis using remote sensing approach

Impact of recent floods on river morphology of Upper Krishna River: a decadal analysis using remote sensing approach

Abstract C055: Hurricane floods and quality of life among gynecological cancer patients in Puerto Rico: A retrospective cohort study

Abstract INTRODUCTION. Previous studies show the devasting impacts of hurricanes on the health outcomes of cancer patients via treatment interruption. However, there is limited information on the impact of floods after the hurricanes on quality of life, within physical and mental domains, especially for island communities such as Puerto Rico which are at high-risk of these events. PURPOSE. In this study we aimed to assess the relationship between floods and quality of life of women diagnosed with gynecological cancers in Puerto Rico after the hurricane season of 2017. Methods. Women (n=271) with gynecological cancers recruited from a clinic-based sample in Puerto Rico were retrospectively interviewed between September 2019 and November 2020. After consenting, one-hour interviews were conducted over the phone to complete a comprehensive survey. This survey collected information on sociodemographic, clinical, lifestyles, and quality of life for all participants. Our primary outcome was quality of life experienced by participants considering the physical and mental domains 3 months after the occurrence of the hurricanes. Pearson’s Chi-square test and logistic regression models were performed using STATA. SUMMARY OF DATA. Participants were mostly 50 years old or older (78.8%), married (51.2%), employed or self-employed (30.4%), had low annual income (<$20,000; 66.9%) and were well educated (41.2% hold a bachelor’s degree). A third of the participants (31%) reported physical distress before hurricanes, compared to 46% post hurricane. In terms of the mental domain, only 25% of participants reported mental distress before the hurricanes, compared to 59% post hurricane (p <0.01). A slight difference in percentage was observed for the need of emotional and social support of the participants pre (92%) and post (93%) hurricane. Half of the participants (51.4%) experienced floods related to the hurricanes. On multivariable analysis adjusted by education, age, income, and history of gynecological cancers, we observed that participants who experienced flooding were more likely to report having physical (AOR, 1.88; 95% CI 1.08-3.25) and mental (AOR, 2.85; 95% CI 1.52-5.35) distress after the hurricanes in comparison to their counterparts. No statistically significant association was observed for other measures such as general health status or the need of emotional or social support. Conclusion. Floods significantly impacted the quality of life of gynecological cancer patients in Puerto Rico following hurricane seasons of 2017. These findings highlight the need to strengthen public infrastructure that will better protect the homes of inhabitants of Puerto Rico, especially cancer patients, when faced with hurricane disasters. Cancer patients already face many obstacles that make it difficult to cope with physical and mental distress, but flooding is a preventable risk that public infrastructure can alleviate. Further research is warranted to understand the duration of impact on quality of life and effects on overall general health, health outcomes, and mortality. Citation Format: Amarilis Bolanos, Sandra Garcia, Jeslie M. Ramos-Cartagena, Ana Patricia Ortiz, Nancy R. Cardona-Cordero. Hurricane floods and quality of life among gynecological cancer patients in Puerto Rico: A retrospective cohort study [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C055.

The Variation in Boulder Bars Triggered by the 2018 Sedongpu Natural Dam Failure in the Yarlung Tsangpo River

Natural dams are formed most often in narrow, steep valleys in high mountains. The outburst floods triggered by natural dam failures result in the topography and landforms successively being altered. Boulder bars are common natural structures that are selected here to quantitatively evaluate the impact of outburst floods on the topographical and landform variations in downstream channels. In this study, we selected the Sedongpu natural dam on the Yarlung Tsangpo River formed as a result of a landslide in 2018 as an example, and studied the geomorphological changes in a river reach located 173 km downstream of the Sedongpu natural dam. The sizes and shapes of the boulder bars in this area were statistically analyzed. The results show that there are three shape types of boulder bars in this area, i.e., sickle, bamboo leaf and oval. Furthermore, it found that the relationship between the lengths and widths of boulder bars is similar before and after outburst floods, as is the relationship between perimeters and lengths of boulder bars, which means these relationships are not affected by outburst floods. And the perimeters of boulder bars are almost twice their lengths. In addition, the relationship between the areas and lengths of boulder bars follows a power function. The most important finding is that the riverine morphological features conserved self-similarity due the influence of the outburst flood erosion triggered by a natural dam failure. This finding adds to the previous observations since dam failures introduce sudden and dominating impacts on river systems.

The Impact of Catastrophic Floods on Macroinvertebrate Communities in Low-Order Streams: A Study from the Apennines (Northwest Italy)

Floods are normal components of many river regimes and, as such, they exert a significant influence at the ecosystem level. In recent decades, however, climate change has increased the frequency and intensity of floods, with serious consequences for lotic biota, particularly benthic macroinvertebrates, due to their limited mobility and sensitivity to disturbance. The impact of floods varies according to different biological parameters including the characteristics of the macrobenthic communities (taxonomic composition, morphology, behaviour, and life history traits) on one hand and various nonbiological parameters such as flood intensity, artificialisation of the river bed, the presence of dams, and many other factors on the other. Understanding these dynamics is pivotal to improve the effective management and conservation of aquatic ecosystems in the context of current climate change. The aim of this short communication is to evaluate the impact of a catastrophic flood on the macroinvertebrate community of a low-order Appennine stream (NW Italy). This will provide data regarding the varying impacts on different taxa and the recovery pattern of this significant component of the ecosystem.

Community Adaptation to Mitigate the Impact of Flooding in Kaoliaw, Sybounhuengthong and Sysomsuen Vilages, Sykhottabong District, Vientiane Capital

Kaoliaw, Sybounhuengthong and Sysomsuen Vilages, Sykhottabong District, Vientiane Capital is one of the areas have been affected by floods every year. The main reason may be due to the geography and the location is a flat area. The construction of embankment blocked the amount of water in the area unable to be drained out, which resulted of flooding in the area. The flood problem caused people need to adapt themselves to survive. Therefore, the purpose of this research is to study the various factors that affect the occurrence of flooding and how the people adapt in the flood area. The research method analyzed the annual rainfall and the maximum of flood using Log Pearson Type III. The population sample interview was used in total of 136 families (3 villages), community's flood adaptation data is analyzed using SPSS. Research results found that the amount of annual rainfall and the number of rain days tend to decrease. SPSS illustrated that the main cause of flooding is inefficient drainage system, followed by heavy rain, which accounts for 44.5% and 20.5% of the total sample group, respectively. The maximum duration of flooding is more than 10 days, but most of them are in the range of 4 to 7 days, which accounts for almost 40% of the sample group. For the community's flood adaptation before the flood, they followed the weather news through television and social media, installed water pumping and built waterproof walls around the house; During the flood, many families had to drain the water from their houses and they have to drop their vehicles outside the flood area. After the flood, people improved their house to make it more flood resistant and plan to deal with the next flood. In addition, the study results can be an important database for relevant organizations to analyze and investigations the solution plan to deal with future floods.

Analisis Spasial Bencana Banjir Di Kota Padang Periode Tahun 2020-2024

During the period of 2020-2024, the frequency and intensity of flooding in the City of Padang showed a significant increase, impacting the community. This study aims to: 1) identify the spatial distribution of flood disasters in the City of Padang, 2) classify the types of floods that occurred, and 3) identify the impact of floods on damage and losses. This type of research is quantitative, with the population being all sub-districts in the City of Padang. The sample was taken using total sampling, covering all sub-districts affected by flooding, totaling 11 sub-districts, including Padang Barat, Padang Utara, Padang Timur, Padang Selatan, Nanggalo, Kuranji, Lubuk Begalung, Lubuk Kilangan, Pauh, Koto Tangah, and Bungus Teluk Kabung. The data analysis technique used is spatial analysis. The results of the study show that there were 121 flood events distributed across various sub-districts, with the highest occurrences in Koto Tangah (56 events) and the fewest in Padang Barat (2 events). Floods in the City of Padang are classified into three categories: fluvial floods, tidal floods, and flash floods. Fluvial floods are the most common, while tidal floods occur in Padang Barat, and flash floods occur in Lubuk Begalung. The impact of the floods includes damage and losses; Lubuk Begalung experienced the most significant damage, with 70 houses affected, and the largest losses occurred in Pauh in 2023, amounting to Rp1,786,150,000, while the lowest losses occurred in Koto Tangah in 2022, amounting to Rp18,000,000.

Mapping Geospatial AI Flood Risk in National Road Networks

Previous studies have utilized machine learning algorithms that incorporate topographic and geological characteristics to model flood susceptibility, resulting in comprehensive flood maps. This study introduces an innovative integration of geospatial artificial intelligence for hazard mapping to assess flood risks on road networks within Portuguese municipalities. Additionally, it incorporates OpenStreetMap’s road network data to study vulnerability, offering a descriptive statistical interpretation. Through spatial overlay techniques, road segments are evaluated for flood risk based on their proximity to identified hazard zones. This method facilitates the detailed mapping of flood-impacted road networks, providing essential insights for infrastructure planning, emergency preparedness, and mitigation strategies. The study emphasizes the importance of integrating geospatial analysis tools with open data to enhance the resilience of critical infrastructure against natural hazards. The resulting maps are instrumental for understanding the impact of floods on transportation infrastructures and aiding informed decision-making for policymakers, the insurance industry, and road infrastructure asset managers.

Assessment of flood vulnerability in Osun River Basin using AHP method

Flooding is a global natural disaster that occurs when water rises over normal levels and damages infrastructure, buildings, and land. Lately, a substantial rise has occurred in the frequency and severity of floods in Nigeria due to urbanization, population growth and climate change. This study aims to identify areas in the Osun River Basin (ORB) in southwest Nigeria that are at risk of flooding as a result of increased rainfall patterns that can induce river flooding. 10 flood factors contributing to flood susceptibility were obtained around the study area. These remote sensing data were analyzed using a weighted overlay on ArcGIS. The Analytic Hierarchy Process (AHP) was particularly applied in analysing the flood factors and creating the flood susceptibility maps. Results obtained showed that flood events are probable in areas along the river bank, some areas that are low-lying terrains and areas where there is high rainfall. Ogun State falls within the areas with the lowest digital elevation, therefore the state is very highly susceptible to flooding from the tributaries of the Osun River. Areas such as Ijebu North, Ijebu North East, Ijebu East and Ijebu Ode were identified as highly susceptible to flooding from the maps created. This study will further help stakeholders and policymakers in reducing the impact of flooding in these areas.

Syndromic Surveillance in Public Health Emergencies: A Systematic Analysis of Cases Related to Exposure to 2023 Floodwaters in Romagna, Italy.

In May 2023, Romagna, Italy, faced a devastating flood resulting in 16 fatalities, forced displacement of 26,000 citizens, and significant economic losses. Due to potential water contamination, implementing public health strategies became imperative for the Local Health Authority to mitigate the health consequences, analyze the flood's impact on the local population's health, and detect early anomalies requiring timely public health interventions. Between June and July 2023, general practitioners who were part of the RespiVirNet surveillance network completed weekly structured forms. These forms collected data on individuals exposed or not to floodwaters and clinical syndromes. Rates per 1000 resident population aged > 14 were stratified by district, week of observation, and symptomatology. Missing data were addressed by imputation using second-order autoregressive modeling. An incidence of 3.52 syndromes potentially related to flood water exposure per 1000 individuals (95% CI 2.82-4.35) was estimated. Ravenna, the city most affected by the flood, recorded the highest rate (6.05 per 1000, 95% CI 4.59-7.82). Incidence decreased in the weeks post-event. Anxiety, or trauma and stress symptoms, exhibited higher rates among the exposed, diminishing over weeks. The incidence for the non-exposed (12.76 per 1000, 95% CI 10.55-15.29) showed no significant territorial differences compared to the exposed ones. Syndromic surveillance provided timely information on the flood's health impact, revealing a higher incidence of individual syndromes among the non-exposed. This study contributes to guiding the implementation of future public health preparedness and response strategies for populations facing similar natural disasters.

Numerical Investigation on Stability of Lanxi’s Ancient City Wall during a Major Flood Propagation Process

Major flood propagation processes often cause instability and damage to the ancient waterfront city walls. To quantitatively reveal the impact of major floods on the stability of ancient city walls, this paper takes Lanxi’s ancient city wall as a study object and constructs a numerical model to investigate the influence of the major flood process in 2017 on the wall stability and reveals the varying laws of its seepage, displacements, maximal shear stresses and safety factors with flood propagation time on the basis of flood level data, combining indoor experiments and field observations. The results show that flood level variations significantly affect the PWPs (pore water pressures) of the fillings behind the wall. During the flood period, the maximal horizontal and vertical displacements are mainly induced by soil extrusion and deformation, and the maximal shear stresses of the outer and inner wall also significantly increase. The changing rates of the wall’s safety factors measurably exceed that of the flood level. The flood level variation range dramatically affects the safety factors when it changes near and above the wall foot. The minimum of the safety factors decreases with the increasing flood level falling rate when it drops near the wall foot at different rates. The ancient city wall usually does not experience serious instability under a single major flood. This study can provide a theoretical basis for the selection of reinforcement measures for flood control ancient city walls and the protection of ancient waterfront buildings.

Merging modelled and reported flood impacts in Europe in a combined flood event catalogue for 1950–2020

Abstract. Long-term trends in flood losses are regulated by multiple factors including climate variation, demographic dynamics, economic growth, land-use transitions, reservoir construction and flood risk reduction measures. The attribution of those drivers through the use of counterfactual scenarios of hazard, exposure or vulnerability first requires a good representation of historical events, including their location, their intensity and the factual circumstances in which they occurred. Here, we develop a chain of models that is capable of recreating riverine, coastal and compound floods in Europe between 1950 and 2020 that had a potential to cause significant socioeconomic impacts. This factual catalogue of almost 15 000 such events was scrutinized with historical records of flood impacts. We found that at least 10 % of them led to significant socioeconomic impacts (including fatalities) according to available sources. The model chain was able to capture events responsible for 96 % of known impacts contained in the Historical Analysis of Natural Hazards in Europe (HANZE) flood impact database in terms of persons affected and economic losses and for 81 % of fatalities. The dataset enables the study of the drivers of vulnerability and flood adaptation due to a large sample of events with historical impact data. The model chain can be further used to generate counterfactual events, especially those related to climate change and human influence on catchments.

Flood Modelling of Madi River Using HEC-RAS by Rain on Grid Approach

Indispensable for prognosticating flood impact in areas with limited data availability, reliable flood models are crucial for the analysis and mitigation of flood hazard. This study provides insight to accurately analyse flood scenarios by preparing a well calibrated 2D hydraulic model in HEC-RAS along with the Rain on Grid approach, which is subsequently used for hazard map preparation of Madi River. Hazard classification of flood depth indicated that for a 20-year return period, Moderate hazard levels covered 16.499%, High hazard levels covered 14.831%, and Very High hazard levels covered 68.670% of the total inundated area with reference to the depth hazard categories. Since, significant portion of the inundated area is classified as Very High Hazard; the finding of this research emphasizes the need of effective mitigation measure and provides essential insights crucial for flood risk assessment.

Impact of Flood on Breastfeeding Practices at Flood Relief Camps of Pakistan.

To explore impact of flood on breastfeeding practices and identify barriers in continuation of breastfeeding among mothers residing in flood relief camps. This exploratory observational study was conducted during visit of medical team of The University of Child Health Sciences, Children's Hospital at flood relief camps of Sindh (7th September to 12th September, 2022) and south-west of Punjab province (18th November to 20th November, 2022). The data was collected on structured questionnaire from 40 lactating mothers residing in flood relief camps. Purposive sampling technique was used in this regard. The mean age of breastfed children was 16.1±7.811 months. There was negative impact on breastfeeding practices (n=21, 52.5%) as frequency decreased in 18(45%) mothers and 3(7.5%) totally stopped breastfeeding. There was significant relation between pre-flood breastfeeding status and impact of flood on breastfeeding practices (p=0.001). The major barriers to appropriate breastfeeding were mother's perception of insufficient breast milk due to inadequate diet (n=6, 15%) or depression and anxiety (n=4, 10%), mother's illness (n=3, 7.5%), constant displacement (n=2, 5%) and provision of breast milk substitutes (n=2, 5%). There has been significant negative impact of flood on breastfeeding practices among lactating mothers residing in flood relief camps. Perception of decreased milk production due to inadequate diet and stress are major barriers in continuation of breastfeeding. Breastfeeding supportive services need to be integral component of flood crisis management.

Impact of floods and landslides on rhizosphere bacterial communities: a high-throughput 16S rRNA gene sequencing study.

This study investigates the diversity and composition of soil bacterial communities in the rhizosphere of Attapadi and Nelliyampathy, prominent hill stations in Palakkad district, Kerala, India. The persistent flooding and landslides in 2018 and 2019 significantly impacted agricultural productivity in these regions. Utilizing high-throughput 16S rRNA gene sequencing (Illumina MiSeq), we conducted a comprehensive analysis of soil samples. Correlative assessments between soil parameters and microbial relative abundance at the phylum level revealed noteworthy positive associations. Notably, nitrogen (N) exhibited a positive relation with Crenarchaeota, Chloroflexi, Actinobacteriota, and Acidobacteriota; pH correlated with Firmicutes; organic carbon (OC) with WPS-2; and phosphorous with Proteobacteria. A total of 31,402 operational taxonomic units (OTUs) were identified, with the highest feature counts observed in undisturbed soils from Attapadi (AUD) and Nelliyampathy (NUD) (13,007 and 12,915, respectively). Disturbed soils in Nelliyampathy (ND) and Attapadi (AD) displayed a substantial decline in microbial diversity and composition, harbouring 1409 and 4071 OTUs, respectively. Alpha and beta diversity indices further underscored the more severe impairment of ND soils compared to AD soils. Interestingly, a majority of ND samples were landslide-affected (four out of five), while flood-affected soils accounted for four out of six AD samples. This indicates that landslides exert a more pronounced impact on microbial diversity and composition than floods. The observed decline in microbial count, composition, and diversity, even after 2years of the disaster, raises concerns about potential threats to agricultural output. The findings emphasize the need for corrective measures, including the incorporation of microbial inoculum, to restore soil fertility in post-disaster landscapes.

HydroSAR: A Cloud-Based Service for the Monitoring of Inundation Events in the Hindu Kush Himalaya

The Hindu Kush Himalaya (HKH) is one of the most flood-prone regions in the world, yet heavy cloud cover and limited in situ observations have hampered efforts to monitor the impact of heavy rainfall, flooding, and inundation during severe weather events. This paper introduces HydroSAR, a Sentinel-1 SAR-based hazard monitoring service which was co-developed with in-region partners to provide year-round, low-latency weather hazard information across the HKH. This paper describes the end user-focused concept and overall design of the HydroSAR service. It introduces the main processing algorithms behind HydroSAR’s broad product portfolio, which includes qualitative visual layers as well as quantitative products measuring the surface water extent and water depth. We summarize the cloud-based implementation of the developed service, which provides the capability to scale automatically with the event size. A performance assessment of our quantitative algorithms is described, demonstrating the capabilities to map the flood extent and water depth with an accuracy of >90% and <1 m, respectively. An application of the HydroSAR service to the 2023 South Asia monsoon seasons showed that monsoon floods peaked near 6 August 2023 and covered 11.6% of Bangladesh in water. At the peak of the flood season, nearly 13.5% of Bangladesh’s agriculture areas were affected.

Social dimensions of climate‐induced flooding in Jakarta (Indonesia): The role of non‐point source pollution

AbstractBecause of its low‐lying location, urbanization, and inadequate infrastructure, Jakarta (Indonesia) has experienced an increase in annual flooding events, rising from an average of five significant floods per year in the 1990s to over 20 annually (2010–2020). With climate change exacerbating extreme weather events, Jakarta encounters escalating risks of flooding. Although the recurrent flooding is exacerbated by non‐point source (NPS) of pollution such as urban runoff and agricultural discharge that contribute to 40% of total pollutants leading to flood‐related issues in Jakarta, none has investigated this research gap. To reflect its novelty, this work explores the implications of climate change on the annual flooding in Jakarta by focusing on NPS and analyzes their impacts from social perspectives. This work also underscores the implications of flooding on livelihoods, health, and social cohesion in Jakarta. Focus group discussion with affected residents was used to shed light on the coping strategies employed in response to recurrent floods, ranging from community‐based initiatives to reliance on informal networks. The empirical findings show that the implications of flooding extend beyond physical damages. Displacement of communities, loss of livelihoods, disruption of essential services, and increased health risks are among the social impacts experienced by local residents. Vulnerable populations, including low‐income communities residing in informal settlements, bear their consequences. Economic losses from flooding amount to USD 500 million annually, impacting over 1 million residents. However, recent interventions have led to a 15% reduction in peak flood levels and a 20% reduction in flood duration in affected areas. Community resilience has also improved, with a 25% increase in flood insurance coverage and a 20% rise in community response initiatives. Overall, this study highlights that climate change exacerbates annual flooding in Jakarta, significantly impacting vulnerable communities through NPS pollution. Addressing the challenges requires integrated approaches combining effective pollution control, resilient infrastructure, and community engagement to mitigate social and long‐term environmental impacts.Practitioner Points Climate‐induced flooding disproportionately affects vulnerable communities in Jakarta. Non‐point source pollution from urban runoff contributes to the severity of flooding in Jakarta. Waterborne diseases, disruption of livelihoods, and reduced access to clean water are major concerns identified in the study. The study highlights the importance of community‐based adaptation strategies to mitigate the impact of flooding and pollution.

Improving rapid flood impact assessment: An enhanced multi-sensor approach including a new flood mapping method based on Sentinel-2 data

Rapid flood impact assessment methods need complete and accurate flood maps to provide reliable information for disaster risk management, in particular for emergency response and recovery and reconstruction plans. With the aim of improving the rapid assessment of flood impacts, this work presents a new impact assessment method characterized by an enhanced satellite multi-sensor approach for flood mapping, which improves the characterization of the hazard. This includes a novel flood mapping method based on the new multi-temporal Modified Normalized Difference Water Index (MNDWI) that uses multi-temporal statistics computed on time-series of Sentinel-2 multi-spectral satellite images. The multi-temporal aspect of the MNDWI improves characterization of land cover over time and enhances the temporary flooded areas, which can be extracted through a thresholding technique, allowing the delineation of more precise and complete flood maps. The methodology, if implemented in cloud-based environments such as Google Earth Engine (GEE), is computationally light and robust, allowing the derivation of flood maps in matters of minutes, also for large areas.The flood mapping and impact assessment method has been applied to the seasonal flood occurred in South Sudan in 2020, using Sentinel-1, Sentinel-2 and PlanetScope satellite imagery. Flood impacts were assessed considering damages to buildings, roads, and cropland. The multi-sensor approach estimated an impact of 57.4 million USD (considering a middle-bound scenario), higher than what estimated by using Sentinel-1 data only, and Sentinel-2 data only (respectively 24% and 78% of the estimation resulting from the multi-sensor approach). This work highlights the effectiveness and importance of considering multi-source satellite data for flood mapping in a context of disaster risk management, to better inform disaster response, recovery and reconstruction plans.

The changing rainfall patterns drive the growing flood occurrence in Phnom Penh, Cambodia

Study regionUrban flooding is an intensifying issue in the rapidly developing lowland cities of Southeast Asia. Cambodia’s Phnom Penh City, located at the confluence of the Mekong and Tonle Sap Rivers in the lower Mekong Basin, recently saw increasingly prevalent flash floods, resulting in casualties and damages. Study focusWhile flood planning and impact assessments have been done in the Mekong basin, flood causes in the face of climate change remain insufficiently understood. In this paper, the drivers of the increasingly prevalent floods in Phnom Penh are investigated through analysis of remote sensing and instrumental data. New hydrological insights for the regionWith precipitation records from the Climate Hazards Group InfraRed Precipitation and gauge station dataset, a general precipitation increase of 7 mm/year and a notable shift to a wetter regime were observed. Strong periodicities of 1/3-year, 1/2-year, 1-year and ∼5-year cycles were also identified, which generally showed a considerable increase in intensity from 1981 to 2021. Over the past 40 years, precipitation patterns have intensified. Yet, the average water levels of the rivers surrounding Phnom Penh have declined by 1–2 m from 1981 to 2021, indicating the pressure from climate change is a major hydrological driver contributing to Phnom Penh's flash floods. Meanwhile, Phnom Penh's vulnerability to flash flooding is also likely aggravated by drastic land use changes, which have increased the city's impervious surfaces and reduced its wetlands by 30 % since the 1980s.