Gully erosion as a natural hazard: the educational role of geotourism

Gully erosion is one of the greatest natural hazards in the loess areas of E. (Eastern) Poland. At the same time, permanent gullies are a major tourist attraction and can provide a basis for the development of geotourism. The study objective was to assess the possibilities of using the loess gullies for educational purposes. Detailed studies were conducted within the municipality of Kazimierz Dolny, an area with an extremely high concentration of permanent gullies. The questionnaire survey of students and tourists (nearly 300 surveys were completed) showed that the respondents’ knowledge of geomorphology was limited, despite their familiarity with gullies. In most cases, they were unable to accurately identify the determinants of gully erosion, its negative effects and methods for preventing it. An assessment of the tourism and geotourism potential of the municipality made it possible to identify the sites (gullies) that can perform an educational function, with regard to gully erosion. The establishment of the Ma?opolska Vistula Gap Geopark, whose highlights will include numerous loess gullies, can pave the way for the development of geotourism.     

Monitoring the temporal development of natural hazard risks as a basis indicator for climate change adaptation

The potential effects of climatic changes on natural risks are widely discussed. But the formulation of strategies for adapting risk management practice to climate changes requires knowledge of the related risks for people and economic values. The main goals of this work were (1) the development of a method for analysing and comparing risks induced by different natural hazard types, (2) highlighting the most relevant natural hazard processes and related damages, (3) the development of an information system for the monitoring of the temporal development of natural hazard risk and (4) the visualisation of the resulting information for the wider public. A comparative exposure analysis provides the basis for pointing out the hot spots of natural hazard risks in the province of Carinthia, Austria. An analysis of flood risks in all municipalities provides the basis for setting the priorities in the planning of flood protection measures. The methods form the basis for a monitoring system that periodically observes the temporal development of natural hazard risks. This makes it possible firstly to identify situations in which natural hazard risks are rising and secondly to differentiate between the most relevant factors responsible for the increasing risks. The factors that most influence the natural risks could be made evident and eventual climate signals could be pointed out. Only with this information can the discussion about potential increases in natural risks due to climate change be separated from other influencing factors and be made at an objective level.     

Application of geomorphologic knowledge for erosion hazard mapping

An erosion hazard map was elaborated using geomorphologic and lithological information; this was the base to characterize the erodibility of the territory. The aim of the proposed methodology is to define the areas where more detailed studies are necessary (e.g., to estimate rates of soil erosion, mitigation measurements, land use) to prevent future problems. Field work and remote sensing data (study of historical aerial photographs and satellite images) were used to understand the geomorphologic evolution and the current processes taking place in an area; this information was used to group the units according to its lithology, dynamic and slope inclination. The map was processed using the geographical information system and categorized in zones of very high, high, moderate, low and null fluvial erosion hazards. The map covers the Metropolitan Area of San Salvador, which is experiencing serious problems of mass wasting processes, collapse and settlements of foundations. Most affected areas belong to the Tierra Blanca Joven tephras which are unsaturated and cover most of the surface; nowadays, the urban projects and infrastructure resting in this material are suffering from extensive damage. The geotechnical information on the tephras shows a decrease in strength and collapsible behavior when saturated. Due to this, the use of Quickdraw tensiometers (suction) and TMS3 (soil moisture content) is proposed for monitoring. The methodology of erosion hazard mapping correlates well with mass wasting reported in the studied area, and for this reason, it could be a good way to protect the natural resources and improve the land use.     

Assessing soil erosion hazard in a key badland area of Central Italy

In this work, an integrated methodology was applied to assess the water erosion hazard in Upper Orcia Valley, an area of Southern Tuscany (Italy), greatly affected by severe denudation processes, that caused the development of widespread badlands. Prediction of areas prone to calanchi badland development was carried out by applying a susceptibility assessment method based on conditional statistical analysis, preceded by a bivariate statistical analysis aimed at selecting the most influential causal factors of erosion. Water erosion rates at badland sites were estimated by means of an empirical statistical method, implemented to evaluate the erosion intensity (Tu denudation index) and based on some geomorphic parameters as independent variables. This methodology allows associating the denudation intensity to the spatial prediction. The validation procedure, based on a random partition of calanchi badland areas, confirmed the efficiency of the spatial zonation of the erosion hazard values. Moreover, the comparison of the estimated erosion rates with the results of decadal investigations on denudation processes affecting the study area, performed by different monitoring methods, showed the effectiveness of the estimation model. These results allowed concluding that the proposed procedure represents a useful tool to be applicable for soil protection strategy planning in land management of Mediterranean areas characterized by similar morphoclimatic features, even when direct erosion rate measures are not available.     

Soil erosion hazard in the Yimeng mountainous region, North China

The Yimeng mountainous region of North China is a unique region with vulnerable ecosystems and under the most pressure from various risk sources. In recent years, this region has experienced rapid economic growth. However, the study area is vulnerable to environmental hazards and is seriously affected by soil erosion due to natural factors and human activities, thereby increasing the risk of environmental degradation in the Yimeng mountainous region of Shandong Province in North China.     

Measuring long-run economic effects of natural hazard

This paper studies the long-run economic effects of severe weather on regional economies. A catastrophic event, such as a hurricane, will have an effect on both the directly impacted region and adjacent regions. With dramatically increasing damage from catastrophic weather events over the past few decades, comprehensive assessment of the long-run economic impact of natural disasters across the broader region becomes more important than ever for planning for post-disaster recovery. We estimate the long-run effect of Hurricane Katrina on the unemployment rate of Houston, TX by employing time-series and fixed-effect models. Using Dallas as a control, we find that Katrina is associated with a higher long-run unemployment rate in Houston than would otherwise have been expected. This implies that the hurricane-generated adverse relative effects on Houston. Our findings suggest that areas that are geographically proximate to the directly impacted region can sustain lasting negative economic consequences.     

Geomorphic natural hazard on loess terrain: expansion on the gully sidewall

Natural Hazards - Gully sidewall expansion is an important geomorphic natural hazard, and the expansion destroys a large extent of agricultural land in the loess regions every year. The main aim of...     

From natural hazard to environmental catastrophe: Past and present

The number of environmental catastrophes is rising, mostly owing to an increase in hydrometeorological hazards. The number of disasters is escalating as the world population grows and people settle in marginal areas. In order to improve preparedness, the geological and archaeological records must be investigated as they hold a wider range of possible events than the much shorter instrumental record. Catastrophes will gain amplitude with rapid onset, long duration, larger affected area, inflexible society and, of course, convergence of threats. Too often, it seems that today's societies resist learning from the past and therefore tend to repeat errors. A new field of science is emerging: the science of environmental catastrophes, which requires not only robust chronologies to firmly link cause and effect, but also bridges the crossing between the geosciences and social sciences.     

Wind erosion hazard assessment of the Mongolian Plateau using FCM and GIS techniques

The most serious environmental problems of the Mongolian Plateau are land degradation and sand storms caused by wind erosion, but the evaluation of wind erosion at regional scales has been a difficult process in wind erosion research. In this study, fuzzy c-means clustering (FCM) was used to assess the spatial pattern of wind erosion hazard on the Mongolian Plateau. By fuzzy clustering four main wind erosion factors (vegetation cover, average degree of land surface relief, degree of soil dryness and intensity of wind energy), wind erosion hazard was classified into six grades. Results show that FCM can effectively integrate related information between wind erosion and environmental factors, which provides the basis for predictive mapping of wind erosion hazard. Spatial patterns of wind erosion hazard indicate a gradual trend of increasing hazard in the Mongolian Plateau from east to west. Similar patterns were also found in NDVI and soil dryness, indicating that soil moisture and vegetation are the most important factors in the formation of wind erosion hazard. In addition, the distribution of different levels of wind erosion hazard is basically consistent with the regional distribution of landscape vegetation types in the Mongolian Plateau.     

Interpersonal communication sources and natural hazard risk perception: a case study of a rural Chinese village

This exploratory study contributes to our knowledge about the relationships between interpersonal communication sources and risk perception regarding natural hazards. Survey data (N?=?186) from a small village in northwest China was used, and the correlations between eight types of interpersonal communication sources related to disaster risk reduction and the perceived severity and perceived likelihood of occurrence of eight types of natural hazards were explored. Past studies have suggested that interpersonal communication sources are more likely to influence individuals in their perceived severity of natural hazards than in their perceived likelihood of occurrence. The results of this study moderately corroborate this finding. The results indicated that different sources have different relationships to risk perception, as positive correlations were found between obtaining information via certain trained science professionals (science teachers, emergency responders, scientific experts) and certain natural hazard risk perceptions, while negative relationships were found between obtaining information via certain personal contacts (other villagers and relatives and friends) and certain natural hazard risk perceptions. However, the strength of these relationships was weak (??0.197?≥?r?≤? 0.245). Age showed statically significant correlations with the perceived severity of most of the natural hazards. Studies with more representative samples and controls for theoretical factors are needed to better understand how interpersonal communication sources affect individuals' natural hazard risk perceptions.     

Gully erosion spatial modelling: Role of machine learning algorithms in selection of the best controlling factors and modelling process

This investigation assessed the efficacy of 10 widely used machine learning algorithms (MLA) comprising the least absolute shrinkage and selection operator (LASSO), generalized linear model (GLM), stepwise generalized linear model (SGLM), elastic net (ENET), partial least square (PLS), ridge regression, support vector machine (SVM), classification and regression trees (CART), bagged CART, and random forest (RF) for gully erosion susceptibility mapping (GESM) in Iran. The location of 462 previously existing gully erosion sites were mapped through widespread field investigations, of which 70% (323) and 30% (139) of observations were arbitrarily divided for algorithm calibration and validation. Twelve controlling factors for gully erosion, namely, soil texture, annual mean rainfall, digital elevation model (DEM), drainage density, slope, lithology, topographic wetness index (TWI), distance from rivers, aspect, distance from roads, plan curvature, and profile curvature were ranked in terms of their importance using each MLA. The MLA were compared using a training dataset for gully erosion and statistical measures such as RMSE (root mean square error), MAE (mean absolute error), and R-squared. Based on the comparisons among MLA, the RF algorithm exhibited the minimum RMSE and MAE and the maximum value of R-squared, and was therefore selected as the best model. The variable importance evaluation using the RF model revealed that distance from rivers had the highest significance in influencing the occurrence of gully erosion whereas plan curvature had the least importance. According to the GESM generated using RF, most of the study area is predicted to have a low (53.72%) or moderate (29.65%) susceptibility to gully erosion, whereas only a small area is identified to have a high (12.56%) or very high (4.07%) susceptibility. The outcome generated by RF model is validated using the ROC (Receiver Operating Characteristics) curve approach, which returned an area under the curve (AUC) of 0.985, proving the excellent forecasting ability of the model. The GESM prepared using the RF algorithm can aid decision-makers in targeting remedial actions for minimizing the damage caused by gully erosion.     

Enhancing the capacities of natural hazard mitigation: a study on a typhoon curriculum module in high school earth science

This study is part of the hazards mitigation education program “research on teaching resources development and curriculum promotion on natural hazards mitigation at high school level.” This study demonstrated the implementation of a newly developed earth science curriculum module of typhoon hazards mitigation in a 10th grade high school classroom in Taiwan. The curriculum module design is a response to the calls for better natural hazards mitigation education in the school systems in Taiwan. Findings show that the curriculum module has resulted in the positive learning outcomes in both students’ learning achievement and attitude toward typhoon hazards mitigation. Findings also suggest that group discussion activities could enhance students’ thinking and experience sharing on the perceptions about typhoon hazards preparedness and mitigation. This study suggests that the hazards mitigation curriculum module to be added as a topic in the national high school curriculum guidelines.     

四川布拖县扎台沟泥石流微地貌及成灾特性

扎台沟为一老泥石流沟,历史上曾多次发生过泥石流。通过野外考察、实验分析和理论计算,扎台沟流域面积4.86km2,主沟长4.53km,主沟平均纵比降420‰。共发育5条主要支沟,流域切割密度2.19km/km2,源头海拔3100m,沟口海拔1197m,主沟相对高差1903m,与西溪河以62°交角汇入。扎台沟为中高频率-中大规模粘性泥石流沟,目前已辩明,近1000a内至少发生过3次大规模泥石流,泥石流重度2.0t/m3,沟道堵塞系数1.5。扎台沟50a一遇和100a一遇泥石流流量分别为155.77m3/s和178.19m3/s;50a一遇和100a一遇泥石流固体物质冲出量分别为16.39×104m3及18.14×104m3,是一条中度危险的泥石流沟,对下游水电站其中一处拟选坝址有一定影响。如无法避开扎台沟泥石流对拟选坝址的影响,可考虑对该泥石流沟采取选择性整治工程措施。     

Gray swans: comparison of natural and financial hazard assessment and mitigation

Even advanced technological societies are vulnerable to natural disasters, such as the 2011 Tohoku earthquake and tsunami, and financial disasters, such as the 2008 collapse of the US housing and financial markets. Both resulted from unrecognized or underappreciated weaknesses in hazard assessment and mitigation policies. These policies relied on models that proved inadequate for reasons including inaccurate conceptualization of the problem, use of a too-short historic record, and neglect of interconnections. Japanese hazard models did not consider the possibility of multiple fault segments failing together, causing a much larger earthquake than anticipated, and neglected historical data for much larger tsunamis than planned for. Mitigation planning underestimated the vulnerability of nuclear power plants, due to a belief in nuclear safety. The US economic models did not consider the hazard that would result if many homeowners could not pay their mortgages, and assumed, based on a short history, that housing prices would keep rising faster than interest rates. They did not anticipate the vulnerability of the financial system to a drop in housing prices, due to belief that markets functioned best without government regulation. Preventing both types of disasters from recurring involves balancing the costs and benefits of mitigation policies. A crucial aspect of this balancing is that the benefits must be estimated using models with significant uncertainties to infer the probabilities of the future events, as we illustrate using a simple model for tsunami mitigation. Improving hazard models is important because overestimating or underestimating the hazard leads to too much or too little mitigation. Thus, although one type of disaster has natural causes and the other has economic causes, comparison provides insights for improving hazard assessment and mitigation policies. Instead of viewing such disasters as unpredictable and unavoidable “black swan” events, they are better viewed as “gray swans” that—although novel and outside recent experience—can be better foreseen and mitigated.     

Probabilistic disaggregation of a spatial portfolio of exposure for natural hazard risk assessment

In natural hazard risk assessment situations are encountered where information on the portfolio of exposure is only available in a spatially aggregated form, hindering a precise risk assessment. Recourse might be found in the spatial disaggregation of the portfolio of exposure to the resolution of the hazard model. Given the uncertainty inherent to any disaggregation, it is argued that the disaggregation should be performed probabilistically. In this paper, a methodology for probabilistic disaggregation of spatially aggregated values is presented. The methodology is exemplified with the disaggregation of a portfolio of buildings in two communes in Switzerland and the results are compared to sample observations. The relevance of probabilistic disaggregation uncertainty in natural hazard risk assessment is illustrated with the example of a simple flood risk assessment.     

四川省泸定县深家沟泥石流特征及危险度评价

2006年7月14日泸定县深家沟暴发了一场灾害性泥石流,平均流速6.3m/s,由于泥石流位于县城,造成了较为严重的财产损失.流域面积小、坡陡、沟道短且比降较大是深家沟的主要特征.深家沟属于中度危险的泥石流沟,该沟一次泥石流最大堆积危险范围10633m2,最大堆积长度为147m,最大堆积厚度为1.45m.其防灾减灾措施主要是植树造林,拦挡排导,提高下游的排导能力.     

Historical felt intensities as a guide to earthquake hazard

Up to 150 years of historical mean felt report data at 32 key Australian towns and cities were tested for completeness and converted to intensity recurrence intervals using extreme‐value analysis. It was found that the backward extrapolation of the mean modelled results of the most recent earthquake hazard study for these same localities fell within the 95% confidence interval derived from the regression of these historical data. Historical maximum felt intensities in the same towns and cities of Australia were used to show that damaging intensities of MM7 (or more) can be expected at susceptible sites at one (or more) of these centres, on average at least once every decade. Hence identification of the susceptible sites in each of these localities should be a priority.     

Evaluation of watershed soil erosion hazard using combination weight and GIS: a case study from eroded soil in Southern China

Natural Hazards - On September 20, 2017, Maria, the eleventh-most intense Atlantic hurricane ever recorded, made landfall at 6:15 am local time, the second category 5 hurricane to strike the island...