Small-scale Floods Research Articles

Understanding the impacts of floods on learning quality, school facilities, and educational recovery in Indonesia.

This research is among the first pieces of work to use the comprehensive school safety (CSS) framework to assess the impacts of floods on quality learning and education infrastructure. The CSS framework is employed here to identify the level of disruption to education services following floods in Jakarta, Indonesia, in 2013. The paper poses three key questions, concerning: (i) disruption to children's access to quality education during the flood emergency in 2013 and the early recovery phase; (ii) the impact of the floods on a school's physical infrastructure; and (iii) the effectiveness and level of success of the 2013 flood responses by relevant stakeholders. Combining quantitative and qualitative strategies, the paper examines the experiences of 100 schools in Jakarta. The findings suggest that the CSS framework offers a more nuanced approach to assessing post-disaster education needs. Moreover, it is also relevant for examining the relationship between the COVID-19 pandemic and relative losses in the education sector.

Expected annual probability of infection: A flood-risk approach to waterborne infectious diseases

This study introduces a new approach for the investigation of infections after an accidental ingestion of contaminated floodwater. The concept of Expected Annual Probability of Infection (EAPI) is introduced and implemented in an infection risk-model approach, by combining a Quantitative Microbial Risk Assessment (QMRA) with the four steps in flood risk assessment. Two groups and exposure paths are considered: adults wading in floodwater and small children swimming/playing in floodwater. The study area is located in Ghana, West Africa. Even though Ghana is one of the most urbanized countries in Africa it has significant problems with water resources management and public health. While cholera is classified as endemic in Accra, the natural and human-made characteristics of the capital makes it prone to flooding. The results of the EAPI approach show that on one hand the concentration of pathogens in floodwater, and thus the risk of infection, decreases with the increase of the flood magnitude. On the other hand, larger floods can spread the pathogens further from the point source, threatening populations previously not identified as at risk by small-scale floods. The concept of EAPI is demonstrated for cholera but it can be extended to other waterborne diseases and also different pathways of exposure, requiring minimal adaptations. For future applications, better estimation of EAPI key components and improvement points are discussed and recommendations given for all the assessment steps.

Past and future changes of the Austrian climate – Importance for tourism

The paper summarizes changes of the climate conditions in Austria impacting tourism as part of an extended literature review. The holistic approach of the study enabled to establish the physical links between emissions created by touristic activities and resultant climate responses. Since the end of the 19 th century, air temperature in Austria increased in all elevations by 1.8 °C (+20% compared to the global land areas). Depending on the scenario, a further increase of less than 2 °C (“Paris target”) to 4 °C (“worst-case scenario”; RCP 8.5) is expected until the year 2100, which means that the number of hot days either will stabilize at the current level (“Paris Target”) or current extreme years will become the new normal at the end of the century (“worst-case scenario”). Regarding snow, as the basic requirement for winter tourism, the natural snow cover duration and snow depth decreased especially in western and southern Austria. Depending on the elevation, a further decline of 10% to 40% (“Paris target”) and 50% to 90% (“worst-case scenario”), respectively, is projected until the year 2100. Sustained warming also reduces the time slots for technical snow production in all elevations. More frequent severe thunderstorms and related small-scale phenomena such as heavy precipitation, hail, squalls, small-scale floods and mudflow avalanches are to be expected to increase, especially in the worst-case scenario. Climate change effects emerge progressively in observation-based tourism-climate indicators and more sustained impacts are projected for the future. The magnitude of climate risks in the second half of the 21 st century can be substantially reduced by rapid, global climate mitigation and adaptation measures. Climatological boundary conditions in Austria have already changed and more profound, human induced changes are expected in future, further increasing impacts relevant for tourism in all seasons of the year. The following implications for tourism management can be deduced from this study: • Sector-specific, immediate and effective climate mitigation and adaptation measures are required to substantially reduce the magnitude of the major tourism relevant climate risks (recession of snow, ice and permafrost; heat stress; thunderstorms and related local extreme events; drought events) in the second half of the 21 st century. • Site- and sector-specific, tailored studies based on downscaled and bias-corrected regional climate model output should be performed to help analyze current and future business-related climate risks together with national climate service providers. • Systematic, coordinated and sector-specific awareness raising for climate change and its causes and impacts is needed to ensure acceptance and increase effectivity of mitigation and adaptation measures both for people working in tourism and the guests. • Targeted operational meteorological early warning systems need to be designed and locally implemented (heat stress; thunderstorms and related local extreme events).

A new indicator for dividing sedimentary rhythms in alluvial deposits: A pollen-based method

Yellow River flooding has occurred many times near Kaifeng City resulting in the formation of a relatively complete sedimentary sequence, which provides a rare research carrier for exploring sedimentary rhythms in alluvium. In this paper, two 25-m-long cores were respectively obtained from suburban (JM core) and urban (SZ core) areas of Kaifeng City, China. Using detailed pollen data, grain size and our previous studies, we explore the effect of Yellow River flood events on the characteristics of alluvial pollen assemblages. Through cluster analysis of the pollen assemblages and pollen concentrations, we determined that there are 16 and at least 14 pollen zones/subzones (i.e. pollen rhythms) in the JM core and SZ core respectively. To aid an objective analysis we define a comprehensive rhythm from three other indicators, namely, grain size, black carbon and anthropogenic-biological elements. For the suburban JM core, less disturbed by human activity, each pollen rhythm has its corresponding comprehensive rhythm, and the upper and lower boundaries are basically the same. However, the number of pollen rhythms is found to be greater than the number of comprehensive rhythms, suggesting the precision of the pollen proxy is higher than the other three indicators. Similar phenomena were found in the SZ core, with significant human disturbance, which also suggests that the pollen proxy is less susceptible to human disturbance and can accurately identify sedimentary rhythms. Furthermore, the pollen concentration and its assemblage characteristics can indicate floods to some extent, even small-scale floods. This is thought to be related to circumstances where some Yellow River floods may have lasted for a long time, during which time there were several relatively short flood intervals due to seasonal and flood path changes; nevertheless, pollen rhythms can also be identified. Consequently, a pollen rhythm may not indicate a specific flood event.

Prediction of hydrological responses to land use change

The change of land use and land coverage (LULC) has a direct impact on the underlying surface of the drainage basin, hence alters the rainfall-runoff processes. This study described the procedure to use the CA-Markov model to predict the future distributed land use in the Qinhuai River basin in 2028 based on the historical evolution. The hydrological model HEC-HMS was then utilized to examine the impact of land use change on the hydrological responses of the drainage basin. The major findings were as follows: (1) from 2001 to 2010, major changes detected in land use were substantial conversion of paddy fields, forest land and dryland into urban land (increased by 56.81%), following the trend recognized by CA-Markov model, urban land and dry land were predicted to increase by 17.47% and 14.05% by 2028. (2) the projected land use in 2028 resulted in various degrees of increase in flood peak and volume according to the severity of the floods characterized by flood volumes, the smaller floods were predicted to result in more significant increase with 3.5% increase in flood peak and 2.9% increase in flood volume while these values decreased to 0.4% and 1.1% for a big scale flood; (3) greater increase in urbanization leads to greater change of the flood peak and volume change. For small scale floods, when the proportion of urban land use increases by 30% to 60% hypothetically, the relative increment in flood peaks increase from 4.7% to 8.1% with 4% to 6.6% increase in the flood volume; (4) on the sub-basin scale, the trend of change in urban land use and the flood peak and volume were consistent. The methods and conclusions may shed light on urban land development and management and design of flood control measures in a large river basin.

Quantifying Disaster Casualties Centered on Flooding in the Chikugo River Middle Basin in the Past 400 Years to Determine the Historical Context of the July 2017 Northern Kyushu Torrential Rainfall

In this study, we collated the number of deaths caused by disasters that took place in the Chikugo River middle basin on the island of Kyushu, Japan, from the 1600s to 2017. The compilation of quantitative statistics of floods in Japan began in the modern era, while the statuses of previous disasters are described by vague indices and are thus difficult to quantify. In this study, we geographically restricted our investigation to the Chikugo River middle basin. We quantified the scale of each disaster by using the number of deaths recorded in historical documents. We then compared the disasters that took place in the area since the 1600s to identify the potential disaster risks harbored by our study area. During the period examined, the great famine from 1732 to 1733 was the greatest disaster and caused the most deaths. However, this is the only recorded famine for which fatalities were documented. Meanwhile, floods occurred frequently through this period, 26 of which resulted in fatalities: they had a total death toll of 292. Thus, famines occur infrequently but cause severe damage, whereas floods occur frequently but cause relatively minor damage. During the approximately 400 years examined, there were four floods with death tolls exceeding 30 people. Three of these occurred after 1868, when the modern era of Japan began. Meanwhile, there have been almost no small-scale floods during and after the modern era. By quantitatively assessing the disasters’ scales, we were able to establish that the 2017 northern Kyushu torrential rainfall was the fourth gravest water-related disaster, in terms of its death, toll since the 1600s. If only the north bank of the Chikugo River middle basin is considered, it was the greatest flood disaster to occur in this period.

Convection-permitting regional climate simulations for representing floods in small- and medium-sized catchments in the Eastern Alps

Abstract. Small-scale floods are a consequence of high precipitation rates in small areas that can occur along frontal activity and convective storms. This situation is expected to become more severe due to a warming climate, when single precipitation events resulting from deep convection become more intense (super Clausius–Clapeyron effect). Regional climate model (RCM) evaluations and inter-comparisons have shown that there is evidence that an increase in RCM resolution and, in particular, at the convection-permitting scale will lead to a better representation of the spatial and temporal characteristics of heavy precipitation at small and medium scales. In this paper, the benefits of grid size reduction and bias correction in climate models are evaluated in their ability to properly represent flood generation in small- and medium-sized catchments. The climate models are sequentially coupled with a distributed hydrological model. The study area is the Eastern Alps, where small-scale storms often occur along with heterogeneous rainfall distributions leading to a very local flash flood generation. The work is carried out in a small multi-model framework using two different RCMs (CCLM and WRF) in different grid sizes. Bias correction is performed by the use of the novel scaled distribution mapping (SDM), which is similar to the usual quantile mapping (QM) method. The results show that, in the investigated RCM ensemble, no clear added value of the usage of convection-permitting RCMs for the purpose of flood modelling can be found. This is based on the fact that flood events are the consequence of an interplay between the total precipitation amount per event and the temporal distribution of rainfall intensities on a sub-daily scale. The RCM ensemble is lacking in one and/or the other. In the small catchment (<100 km2), a favourable superposition of the errors leads to seemingly good CCLM 3 km results both for flood statistics and seasonal occurrence. This is, however, not systematic across the catchments. The applied bias correction only corrects total event rainfall amounts in an attempt to reduce systematic errors on a seasonal basis. It does not account for errors in the temporal dynamics and deteriorates the results in the small catchment. Therefore, it cannot be recommended for flood modelling.

Hidden disasters: Recurrent flooding impacts on educational continuity in the Philippines

This study provides insights on the impacts of both large and small-scale floods in the education sector of Metro Manila, Philippines and how they may contribute in Global Leaning Crisis. It highlights the impacts of small-scale floods which are often unrecognised as they fail to meet the very definition of disaster with the widest global consensus. The methodological framework for this study consists of three different methods including secondary data collection, focus group discussion, and workshop involving students, teachers, school administrators and staffs from selected public schools. Findings suggest that impacts of small-scale floods to school communities (students, teacher and staffs) particularly to the most marginalised students were considerable and their cumulative impacts may be comparable or more important than large-scale floods. Yet, they remain poorly documented and are not addressed by any disaster risk reduction policies in the country. In addition, local capacities of school communities which are more apparent in times of small-scale floods are also neglected. The study then argues that meaningful policies and actions which aim to reduce disaster risk and thus address global learning crisis in the education sector should fully consider small-scale disasters and floods.

Reflection of typhoon morakot — the challenge of compound disaster simulation

Climate change has altered locally single-type disasters to large-scale compound disasters because of increasing intensity and frequency of extreme rainfall events. The compound disasters can combine small-scale floods, debris flows, shallow landslides, deep-seated landslides, and landslide lakes into a large-scale single disaster event. Although simulation models and evaluation tools are available for single-type disasters, no single model is well developed for compound disasters due to the difficulty of handling the interrelationship between two successive single-type disasters. This study proposes a structure for linking available single-type simulation models to evaluate compound disasters and provides a useful tool of decision making for warning and planning of disaster reduction.

Statistical bed load analysis of small-scale floods based on hydrophone observation

Statistical bed load analysis of small-scale floods based on hydrophone observation

Dynamics of coupled human-landscape systems

A preliminary dynamical analysis of landscapes and humans as hierarchical complex systems suggests that strong coupling between the two that spreads to become regionally or globally pervasive should be focused at multi-year to decadal time scales. At these scales, landscape dynamics is dominated by water, sediment and biological routing mediated by fluvial, oceanic, atmospheric processes and human dynamics is dominated by simplifying, profit-maximizing market forces and political action based on projection of economic effect. Also at these scales, landscapes impact humans through patterns of natural disasters and trends such as sea level rise; humans impact landscapes by the effect of economic activity and changes meant to mitigate natural disasters and longer term trends. Based on this analysis, human-landscape coupled systems can be modeled using heterogeneous agents employing prediction models to determine actions to represent the nonlinear behavior of economic and political systems and rule-based routing algorithms to represent landscape processes. A cellular model for the development of New Orleans illustrates this approach, with routing algorithms for river and hurricane-storm surge determining flood extent, five markets (home, labor, hotel, tourism and port services) connecting seven types of economic agents (home buyers/laborers, home developers, hotel owners/ employers, hotel developers, tourists, port services developer and port services owners/employers), building of levees or a river spillway by political agents and damage to homes, hotels or port services within cells determined by the passage or depth of flood waters. The model reproduces historical aspects of New Orleans economic development and levee construction and the filtering of frequent small-scale floods at the expense of large disasters.

Detecting temporal changes in the extent of annual flooding within the Cambodia and the Vietnamese Mekong Delta from MODIS time-series imagery

This paper presents the methodology used to detect temporal changes in the extent of annual flooding within the Cambodia and the Vietnamese Mekong Delta (VMD) based on MODIS time-series imagery (Wavelet-based Filter for detecting spatio-temporal changes in Flood Inundation; WFFI). This methodology involves the use of a wavelet-based filter to interpolate missing information and reduce the noise component in the time-series data, as proposed in a previous study. The smoothed time profiles of Enhanced Vegetation Index (EVI), Land Surface Water Index (LSWI), and the Difference Value between EVI and LSWI (DVEL) are obtained from MOD09 8-day composite time-series data (resolution: 500 m; time period: 2000–2005). The proposed algorithm was applied to produce time-series inundation maps (WFFI products) for the five annual flood seasons over the period from 2000 to 2004. The WFFI products were validated via comparisons with Landsat-derived results and inundation maps based on RADARSAT images, hydrological data, and digital elevation model data. Compared with the RADARSAT-derived inundation maps at the province level, the obtained RMSE range from 364 to 443 km 2 and the determination coefficients [ R 2] range from 0.89 to 0.92. Compared with Landsat-derived results at the 10-km grid level, the obtained RMSE range from 6.8 to 15.2 km 2 and the determination coefficients [ R 2] range from 0.77 to 0.97. The inundated area of flooded forests/marsh to the northeast of Tonle Sap Lake were underestimated, probably because of extensive vegetation cover in this area. The spatial characteristics of the estimated start dates, end dates, and duration of inundation cycles were also determined for the period from 2000 to 2004. There are clear contrasts in the distribution of the estimated end dates and duration of inundation cycles between large-scale floods (2000–2002) and medium- and small-scale floods (2003 and 2004). At the regional scale, the estimated start dates for the southern part of An Giang Province during 2003 and 2004 was distinctly later than that for surrounding areas. The results indicate that these triple-cropping areas enclosed by dikes increased in extent from 2003 to 2004. In contrast, the estimated end dates of inundation at the Co Do and Song Hau State Farms were clearly earlier than those for surrounding areas, although the estimated start dates were similar. Temporal changes in the inundation area of Flood pixels in the Dong Thap and Long An Provinces are in excellent agreement with daily water-level data recorded at Tan Chau Station. The estimated area of Long-term water body increased in size from 2000 to 2004, especially in coastal areas of the Ca Mau and Bac Lieu Provinces. Statistical data for Vietnam indicate that this trend may reflect the expansion of shrimp-farming areas. The WFFI products enable an understanding of seasonal and annual changes in the water distribution and environment of the Cambodia and the VMD from a global viewpoint.

Water systems and risk analysis

Worldwide the water management sector is about to review the design standards for water systems, as expected climate changes may possibly increase the frequency of flood events. This paper reviews new flood standards for surface water systems in The Netherlands, also presenting a cost-benefit analysis. Flood standards were formulated after several serious incidents in 1998 and 2001 to inform residents about the level of protection that they may expect to receive. At this moment all water boards are about to evaluate their water systems using these standards. The cost-benefit approach has been applied to determine whether the necessary measures to comply with such standards were cost-effective. We found that the standards make too much a simplification of the variety of water systems, and lead to costly measures without being beneficial while many small-scale floods in The Netherlands do not cause any significant damage. A better starting point to anticipate on climate change is to prevent damage, instead of the prevention of flooding.

Impact des aménagements hydrauliques sur le régime et la dynamique de la Loire amont. Implications pour la gestion du fleuve. / Impacts of hydraulic works on the hydrological regime and the morphodynamics of the upper Loire : implications for the management of the river

In the Massif Central, the upper Loire river is influenced by hydroelectric works. Measurement of the effects shows a major impact on hydrological conditions on an annual, monthly and daily basis, as well as the elimination of medium and small-scale floods. As resources of sediments have dried up, due to reafforestation, gravel extraction and embanking works, for more than a century the Loire's river bed in the Forez area has become further entrenched. The dams associated with the hydro-electric schemes have accentuated this process by reducing the transport of bed load, drying out the substrate and considerably reducing the necessary upply of coarse material. A restoration programme designed to pave the river is envisaged although not yet started despite its urgency.