This work is a review of the use of hysteresis to quantify sediment discharge dynamics. We reviewed 71 journal articles from the year 1953 to the present day focusing on two topics: the factors that influence hysteresis; and hysteresis quantification. The main factors influencing hysteresis are: (a) magnitude and sequence of events; (b) sediment particle size distribution; (c) basin size; and (d) land use and sediment source. Hysteresis quantification can be done using several different methods that can be grouped as: (a) hysteresis indexes; (b) statistical analysis; and (c) uncertainty analysis. Most studies were conducted in Western Europe and the USA. The studies, in general, show how the factors listed above influence the shape and patterns of hysteresis. However, the sediment dynamics are complex, and the hysteresis patterns may be linked to many other factors, such as slope and drainage systems. The quantification of hysteresis still appears, mainly with the hysteresis index and statistical analysis. Therefore, there are still many many other factors that influence hysteresis patterns, as well as hysteresis rates and uncertainty analyses.
Abstract. Despite the increasing body of research on flood vulnerability, a review of the methods used in the construction of vulnerability indices is still missing. Here, we address this gap by providing a state-of-art account on flood vulnerability indices, highlighting worldwide trends and future research directions. A total of 95 peer-reviewed articles published between 2002–2019 were systematically analyzed. An exponential rise in research effort is demonstrated, with 80 % of the articles being published since 2015. The majority of these studies (62.1 %) focused on the neighborhood followed by the city scale (14.7 %). Min–max normalization (30.5 %), equal weighting (24.2 %), and linear aggregation (80.0 %) were the most common methods. With regard to the indicators used, a focus was given to socioeconomic aspects (e.g., population density, illiteracy rate, and gender), whilst components associated with the citizen's coping and adaptive capacity were slightly covered. Gaps in current research include a lack of sensitivity and uncertainty analyses (present in only 9.5 % and 3.2 % of papers, respectively), inadequate or inexistent validation of the results (present in 13.7 % of the studies), lack of transparency regarding the rationale for weighting and indicator selection, and use of static approaches, disregarding temporal dynamics. We discuss the challenges associated with these findings for the assessment of flood vulnerability and provide a research agenda for attending to these gaps. Overall, we argue that future research should be more theoretically grounded while, at the same time, considering validation and the dynamic aspects of vulnerability.
Abstract:The Civil Defense in Brazil needs to identify and differentiate floods and flash floods for the official registry. This study aims to quantitatively define and differentiate between floods and flash floods. Floods and flash floods are characterized by factors including the speed of water level rise and water flow; the hydrological response time to a rainfall event and the extension of the flood affected area. The hydrological definitions are ambiguous and make it difficult to distinguish between a flood and flash flood event. Even though some papers have mentioned that flash floods occur within 6 hours after an intense rainfall event, there is still certain subjectivity. This study proposes the use of the Operation Efficiency Index (OEI) as a quantitative means to distinguish between a flood and flash flood event. The OEI is defined as the rate of the time of flood concentration (Tc) to the operational response time (To) in the institution-community system. Tc and To are associated with environmental and human factors, respectively. When the OEI value is smaller than one, then flash floods occur. Otherwise the event can be defined as a flood.
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