Course Of Flood Research Articles

Towards the understanding of the flash flood through isotope approach in Kedarnath valley in June 2013, Central Himalaya, India

During middle June 2013, Kedarnath valley in Rudraprayag district of Uttarakhand, India, was affected by catastrophic rainfall episode that caused massive loss of human lives and damage to the properties and livestock. Isotopic signatures of rainfall, snow/ice melt water and river water of Mandakani River were measured from 25 May 2013 to 16 June 2013, and these isotopic signatures are used to estimate the contribution of rainfall-derived runoff on flooding day. The result indicates that during the course of flood in Mandakani River, isotopic signature of river water was −15.97 ‰, whereas average isotopic signature of river before the flood shows −10.39 ‰. By using the two-component mixed model, the contribution of rainfall-derived runoff is found to be 78 % and the contribution of snow/ice melt runoff is 22 % during the flash flood in Mandakani River surrounding the Shri Kedarnath Temple, Central Himalaya, India.

Assessing the retention capacity of a floodplain using a 2D numerical model

Assessing the retention capacity of a floodplain using a 2D numerical modelThis paper presents a method for assessing the retention capacity of a floodplain in the course of flooding and for estimating the significance of its water storage for transforming a flood wave. The method is based on two-dimensional numerical modeling of the flood flow in a river channel and in the adjacent floodplains, and is suitable for cases when the morphology of the flooding area is variable and complex, e.g. broad inundation areas with meandering channels. The approach adopted here enables us to quantify the retention capacity for inundation areas of various characters and with various land uses, and provides a tool for estimating the efficiency of possible measures for increasing the water storage capacity of a floodplain. The retention capacity is estimated using an evaluation of a series of detailed flood flow modeling results; the flood wave transformation effect is predicted with the aim of creating a non-linear reservoir model. A parametric study of the floodplain retention capacity for the upper branch of the Lužnice River is presented here, and the results for the current state and for various hypothetical scenarios of changes in geometry and land use are evaluated and compared.

Sedimentation-induced eutrophication in large river floodplains – An obstacle to restoration?

Conservation and restoration of floodplain ecosystems and their specific functions often suffer from a deficient knowledge on basic processes and dynamics such as sedimentation and related nutrient inputs. In this study, we present the results of a joint analysis of site conditions and vegetation of alluvial meadows along a gradient of increasing distance to the main channel of the river Rhine. In particular we scrutinized whether the flooding frequency mediated by the ground elevation or the distance to the river channel determines the degree of eutrophication by river water and sediments. We found a remarkably strong transversal gradient in the functional floodplain. Extremely high concentrations of CAL-soluble phosphorous (more than 150 mg kg −1) were measured in close proximity to the main channel. These sites were characterized by low vascular plant species richness and a significantly higher proportion of species with high nutrient demands. At a distance of 300 m from the main channel P concentrations in the soil dropped to a quarter of this figure, whereas the average species richness per plot strongly increased. Contrary to our expectations, the influence of the flooding duration was of minor importance for the nutrient status. We can specify that strong eutrophication effects induced by sediment deposits are confined to the close proximity to the main channel within a distance of 200–300 m. At more distant sites, target vegetation of flood meadows was obviously not affected by recent nutrient input in the course of flooding. Concerns by conservationists that the restoration of active floodplains by the removal of dykes will generally lead to unwanted eutrophication by river water and sediments require revision and thorough specification.

Applicability of hydromorphological monitoring data to locate flood risk reduction measures: Blanice River basin, Czech Republic

This paper presents a new methodological approach, using hydromorphological monitoring data from river networks, to identify stream elements that may negatively influence the course of floods, as well as elements suitable for modifications that will reinforce the natural retention potential of the floodplain. The approach uses data derived from hydromorphological monitoring that conforms to the EN 14614 standard "Water quality--Guidance standard for assessing the hydromorphological features of rivers." Four major aspects of stream modifications that can potentially affect the course and consequences of floods, and that can be derived from hydromorphological monitoring, were identified. These are: (1) modifications that increase the speed of runoff, (2) modifications that restrict the retention potential of the floodplain, (3) potential obstacles to the flood course, and (4) improper alterations of stream route modifications. A GIS is used to identify and locate these critical aspects of stream and floodplain modification. This method was applied in the Blanice River basin, an area in central Europe hit by a severe flood in August 2002. The critical modifications identified were compared with geomorphological mapping to display the different effects of individual types of modifications.

Modelling the impact of anthropogenic modifications to river channels on the course of extreme floods. Case study: August 2002 flood, Blanice River basin, Czechia

This paper presents the results of analysis of the impact of anthropogenic modifications to river channels on the course of floods by means of hydraulic modelling. The study is focused on the quantitative analysis of changes of the flow dynamics in the river bed and in the inundation zone due to river network modifications. The one-dimensional hydraulic model HEC-RAS coupled with GIS is used to simulate the effect of the river channel changes on the course of extreme flood. The analysis is made on the example of the extreme flood in August 2002 on the down course of Blanice River in Czechia. The results of the simulations proved that the common anthropogenic modifications of river channel have only a minimum impact on the overall course of extreme floods. At the local level, weirs and unsuitably dimensioned bridges have a negative impact on the course of floods. The simulations also showed a negative impact of extensive complex modifications of the river bed, performed in the lower course of Blanice River in the first half of the 20th century. However, the overall impact of common types of river channel modifications on peak flows and water levels in the culmination is negligible.

Effect of the Hydraulic Characteristics of a Stream Channel and its Surroundings on the Runoff Hydrograph

The course and magnitude of a rainfall flood depends primarily on the intensity and duration of the rainfall event, on the morphological parameters of the watershed (e.g. its slope and shape), and on how to watershed has been exploited. A flood wave develops in the stream channel that drains the watershed, and it transforms while passing along the channel. This is particularly the case if the water spreads into floodplains and/or storage reservoirs while passing through the channel. This paper addresses an additional effect that has a significant influence on the magnitude and course of the flood wave but has not previously been addressed adequately, namely the effect of the hydraulic parameters of the stream channel itself on the transformation of a flood wave. The paper explains theoretically and shows on a practical example that a smooth channel with a high capacity significantly increases the magnitude and speed of a flood wave.Many flood events are unnecessarily severe just because the watershed is drained by a hydraulically inappropriate channel. The channel is large and smooth and therefore it gathers most of the flowing water during the flood event, producing high water velocity in the channel. As a result, the large and smooth channel accelerates the runoff from the watershed and constrains the spread of water into the floodplain. A high and steep flood wave is developed in the channel, and this floods areas with a limited water-throughput capacity (e.g. urban areas in the vicinity of hydraulic structures) downstream the channel. This paper offers a methodology for evaluating the ability of a channel to convey a flood wave safely and for recognizing whether a regulated channel should be subjected to restoration due to its inability to convey flood waves safely.

Present approaches to evaluation of anthropogenous changes in landscape as a factor of flood risk

Flood risks can be evaluated from two points of view, the economic and the process one. The economic approach parts from consequences of the causal event when the risk is defined as the function of probability of occurrence of a certain phenomenon and of potential damage. The process approach evaluates the risk via main processes and factors involved in the risk development. The risk is then defined on the basis of three factors - hazard, exposure, vulnerability (Barredo et al. 2005, Crichton 1999, Kron 2003). Anthropogenous changes in the landscape represent, according to the process approach to risks, one of the vulnerability factors. Vulnerability of environment in relation to values exposed to the hazard represents their susceptibility to damage occurrence and is decisive for the extent of damage. Large changes in intensity, character and structure of land-use occurring in the cultural landscape during these last centuries, affect changes in outflow conditions of the catchment and can thus influence the course of floods. Vulnerability is a risk element which can be, differently from the other risk components, at least partly influenced and controlled. While natural processes representing a source of hazard cannot be influenced and accumulation of property in flood areas can be only hardly reduced, it is possible to purposefully reduce vulnerability both of natural environment and of social links in a way to minimize consequences of natural elements activities, to increase the efficiency of flood control measures and to limit damages to a strict minimum corresponding to the extremity of the phenomenon.

Flood Water Temperature and Duration Affect Nonstructural Carbohydrate Concentration of Cranberry Uprights and Roots

Flooding is often used as a pest management tool in cranberry production. The “Late Water” flood is a 1-month flood held on some Massachusetts bogs from mid-April to mid-May, and has anecdotally been related to poor vine performance. The flood was simulated at 11 °C and 21 °C on potted cranberry uprights (cv. Stevens). Over the course of the 1-month flood, total nonstructural carbohydrate concentration (TNSC) of the upright tissue decreased by 23% and 50% in the 11 °C and 21 °C treatments, respectively. Decreases in upright TNSC in the 11 °C treatment were mostly due to a substantial decrease in sucrose, while in the 21 °C treatment, sucrose, glucose, fructose, and starch all decreased significantly over the course of the flood. The greatest decrease in upright TNSC in the 11 °C treatment occurred during the first week of the flood, while in the 21 °C treatment, the greatest decrease occurred during the fourth week. Root TNSC was not affected by flooding in the 11 °C treatment, but was reduced by 39% in the 21° C treatment. Two weeks following removal from the 1-month flood, uprights in the 11° C treatment contained 9% more TNSC than uprights in the 21 °C treatment, while root TNSC from the two treatments was similar. No temperature treatment differences were evident in the uprights or roots by harvest.

Geoecological aspects of flood origin and consequences

Natural and human factors affect the origin and course of floods in various combinations dependently on the scale. The role of global, regional, landscape and local level flood factors is discussed. The importance of the geographical position of the site endangered by a flood is also evaluated.

Experimental Study of the Flooding and Appearance of a Bubble Bed on Top of a Countercurrent Packed-Bed Column

This paper presents an experimental study of the countercurrent packed-bed column in the course of flooding and above the flooding point when the column operates as a packed bed and a bubble bed in series. Pressure-drop and liquid-holdup data are presented for the packed- and bubble-bed parts of the system. The experiments show that for the two beds in series the hydrodynamic conditions within the packed-bed part are similar for various gas−liquid velocity conditions. The pressure drop in the initial stage of flooding is essentially independent of gas−liquid velocities. The porosity of the forming bubble bed is initially high/low for high/low liquid velocities. For expanded bubble beds their porosity increases with increasing gas velocities.

Surface films as mosquito larvicides: partitioning the mode of action

AbstractOils and other surface films used against mosquito larvae may act by flooding the tracheal system with oil, by disrupting the surface forces that allow larvae to rest at the surface, by toxicity, or by eliciting chemosensory responses. In an attempt to identify diagnostic symptoms of these modes of action we treated fourth‐stage larvae of Culex pipiens L. form molestus Forskål (Diptera: Culicidae: Culicinae) with agents operating in a single mode (Ondina oil for flooding with oil, nicotine for toxicity, and the detergent Triton X‐100 for disruption of surface forces), in two modes (silicone oil) or in three (eucalyptus oil, citronellal, or caproic acid ethyl ester). We monitored the time course of flooding and immobilisation, used experiments to separate volatile toxicity from toxicity of the aqueous solution, and used video and The Observer software to analyse larval behaviour.Larvae that experienced tracheal flooding applied their mouthparts to the siphon (tail nibbling), often losing contact with the surface while doing so and falling to the bottom. Nicotine immobilised larvae without interfering with surface forces, and the larvae remained immobile hanging from the air‐water interface for long periods. In detergent, larvae made repeated unsuccessful attempts to thrust the siphon through the surface. The behaviour‐modifying chemicals caproic acid ethyl ester, eucalyptus oil and citronellal all operated in more than one mode. They all decreased the proportion of time larvae spent at the surface, whereas Ondina oil and silicone fluid increased it.Using this approach it should be possible to identify the modes of action of novel larvicidal agents. This could form a basis for rational design of larvicides giving an optimal compromise between efficacy against mosquito larvae and minimal damage to non‐target organisms.

Effect of flooding on tomato cultivars: The relationship between proline accumulation and other morphological and physiological changes

Flooding of the root system of tomato plants (Lycopersicon esculentum) caused cessation of leaf elongation, leaf epinasty, formation of adventitious roots, and increase in diffusive resistance associated with the wilting of leaves at the first stage of the stress. Upon development of adventitious roots, the wilted leaves regained their turgor and the diffusive resistance slowly decreased at a rate slower than that at which water potential increased. In the course of flooding, proline accumulated but after 11 days dropped back to the control level. The extent of proline accumulation in various tomato cultivars was positively correlated with the extent to which their leaf water potential dropped, but was not correlated with the changes in their diffusive resistance. Cultivars which accumulated the highest proline levels were those which showed the most severe injury, with only one cultivar as an exception. However, only in the cultivars producing high levels of proline was the return of leaf turgor followed by resumption of leaf elongation. In cv. ‘Hosen’, which was severely injured by the stress, but accumulated a low level of proline, leaf elongation was not resumed. The results suggest that proline accumulation is an indicator of the cultivar's sensitivity to dehydration associated with the flooding stress, and confirm the notion that proline may play a role in the post‐stress recovery process.

Brief flooding treatment for a debilitating revulsion

Anger, hostility and revulsion are strong negative emotions which are in many ways like fear and anxiety in that both can have debilitating effects on patients. These debilitating effects usually take two forms: behavioral inhibitions and subjective discomfort. In recent years, behavior therapists have developed several ways of dealing with the latter two emotions, especially as they are present in phobias and other neuroses. Chief among the techniques which have been shown effective are systematic desensitization (Wolpe, 1958) and flooding (Marks, 1972). By extrapolation, one might expect the latter two techniques to be useful in treating other negative emotions. In an analogue study. O'Donnel (1971) found ‘standard’ systematic desensitization based on deep relaxation more effective than control conditions, including variants of systematic desensitization in which relaxation training was omitted, in reducing anger and disgust felt by white students toward racial stimuli. In a second analogue study, however, Harding (1970) found on all of his dependent measures of anger and hostility towards academic situations no differences between subjects treated by systematic desensitization and other control conditions including a no-treatment control group. Finally, Rimm et al. (1971) in another analogue study showed systematic desensitization to be more effective than two control conditions in reducing anger felt in driving situations. Turning to actual clinical cases, one finds very few examples: Herrell (1971) reported the treatment of inappropriate anger responses by a soldier. The patient showed uncontrollable anger and overt acts of aggression at commands. Although no systematic data were collected, it was reported that after 18 sessions of systematic desensitization the patient no longer experienced the negative emotions and the therapeutic gain had transferred to his natural environment. Hogan (1969) mentions using implosive therapy for aggressive feelings of patients and relates some anecdotal data but presents no specific case of data on the topic. The present report concerns the treatment of a debilitating revulsion or anger through a brief course of flooding and as such is novel in two respects: (1) very few other clinical cases of the treatment of anger and revulsion have been reported in the behavior therapy literature and none with detailed dependent measures, (2) the analogue studies have used systematic desensitization rather than flooding.