Likelihood Of Flooding Research Articles

Drivers of change in the Social-Ecological Systems of the Gwydir Wetlands and Macquarie Marshes in northern New South Wales, Australia

The Murray–Darling Basin is a Social-Ecological System (SES) of major importance to Australia and includes extensive wetland areas in the north-western parts of New South Wales. The Gwydir Wetlands and the Macquarie Marshes are the particular focus of this paper. These two wetland SES have undergone five successive adaptive cycles (phases) since they were first visited by Europeans in the early 19th century and the ecological, economic and social drivers initiating each transformation to a new cycle are described and analysed. The arrival of the European settlers with their domestic livestock rapidly displaced the Indigenous SES and the wetlands were extensively grazed; during wet periods the livestock were moved out of the wetlands and moved back in as the water receded. More recent land-use changes resulted from the building of major dams to enable storage of water for use in irrigated agriculture. A consequence of dam construction and water use has been a reduction in the frequency and extent of flooding, which has allowed many parts of the wetlands to be continually grazed. Furthermore, as machinery capable of cultivating the very heavy textured soils became available, dryland cropping became a major enterprise in areas of the floodplain where the likelihood of flooding was reduced. With the reduction in flooding, these wetland sites have been seriously degraded. The final phase has seen the invasion by an exotic weed, lippia [Phyla canescens (Kunth) Greene], which is a perennial that grows mat-like between other species of plants and spreads to produce a virtually mono-specific stand. The domestic livestock carrying capacity of the land becomes more or less zero and the conservation value of the wetlands is also dramatically decreased. Therefore, we suggest that lippia should be classed as an ecosystem engineer that has caused the latest transformation of these wetland SES and suggest research directions to investigate how they can be managed to revert to a state in which lippia is no longer dominant.

Inundation extent as a key parameter for assessing the magnitude and return period of flooding events in southern Iceland

River flow conditions in many watersheds of Iceland are particularly disturbed during winter by the formation, drifting and accumulation of river ice, whose impact on water encroachment and extent of inundations is not reflected in the discharge records. It is therefore necessary to use river discharge with great caution when assessing the magnitude of past inundations in Iceland, and to give attention to other flood magnitude parameters. A GIS-based methodology is presented that focuses on inundation extent as an alternative parameter for the assessment and ranking of the magnitude of past flooding events in the Ölfusá-Hvítá basin, known as one of the most dangerous flood-prone river complexes in Iceland. Relying ultimately on a macro-scale grid, the method enabled the reconstruction of the extent of inundations, the delineation of the flood plain, and, finally, some estimation of the likelihood of flooding of exposed areas that include marine submergences and river floods for both open water and ice conditions. Citation Pagneux, E., Gísladóttir, G. & Snorrason, Á. (2010) Inundation extent as a key parameter for assessing the magnitude and return period of flooding events in southern Iceland. Hydrol. Sci. J. 55(5), 704–716.

Catchment Size, Soil Type and Land Use to Determine the Amount and Likelihood of Flood in the Sarawak Corridor of Renewable Energy (SCORE) Region

Size of catchment, soil types and land use are some of the factors that influence the flood phenomenon. Generally, the amount and behavior of the runoff from precipitation are analyzed to observe their effects on the catchment in terms of flood occurrence. This study measures the likelihood of flood event by comparing the peak flow rates at the pre development and post development stages of the major system. The approach used is by the most common practice in hydrology that is Rational Method. With a higher peak flow rate obtained at post development stage, it has been proven that as more urbanization takes place, there is the more flood occurrence. Similar results are obtained where the poorly-drained soils like peat and clay are present at certain area in the region. It has been verified that the size of catchment contributes the most on the flood risk.

Reintroducing wood to streams in agricultural landscapes: changes in velocity profile, stage and erosion rates

AbstractHistorically, perceived increases in erosion and flooding levels have been attributed to in‐stream wood and used to justify its removal from streams and rivers around the world. More recently, recognition of the adverse morphological and biological impacts caused by this removal has led to rehabilitation projects that actively reintroduce wood to streams. However, a perception remains amongst some members of the general community that wood additions increase the likelihood of flooding and erosion in the target streams.To test whether there was a basis for this perception, we experimentally added wood to eight streams across southwest Victoria and Gippsland, Australia. The velocity, stage and bed and bank erosion rates were compared with those of unaltered reaches. We detected localized changes in the velocity and stage parameters but that these were unlikely to operate at the reach‐scale. Bed erosion rates, where maximum erosion was assumed if pins were not recovered, showed increased erosion due to wood additions but this was not supported by channel shape analyses, which identified short‐term increases in the variability of the channel shape, followed by longer‐term stability at treatment sites.We found no clear evidence of increased longer‐term rates of erosion or flooding associated with the introduction of wood to streams over the 18‐month study period. It remains important to carefully design rehabilitation works, but the lack of adverse effects on stream morphology and increased variability of the in‐stream environment suggests improved habitat diversity, supporting the use of wood addition as a stream rehabilitation technique. Copyright © 2008 John Wiley & Sons, Ltd.

A Factorial Analysis of Storm Surge Flooding in Barrow, Alaska

Abstract This paper describes work to improve the understanding of the broad range of factors affecting the occurrence of flooding in Barrow, Alaska, using as a basis the series of extreme events that have affected the community over the past 50 years. A numerical weather prediction model and a storm surge inundation model have been applied to the 21 case studies identified in National Weather Service data as high wind events. Based on this simulation work flow, a reduced-form model that adequately describes the flooding response has been developed. Specifically, it was found that when wind is forecast to be greater than 13 m s−1 (30 mph) for at least 20 h, this is the most accurate predictor of the possibility of damaging flood. It was found that wind direction, the magnitude of fetch to the sea ice edge (when present), and maximum wind speed were in contrast relatively small contributors to the likelihood of flooding.

Planning policy and flood risk: The translation of national guidance into local policy

Scientists and policy-makers generally agree that the likelihood of flooding in the UK will increase as a result of climate change. It is also accepted that sensible land use and development planni...

Urban riverbank residents’ evaluation of flood evacuation policies in Winnipeg, Manitoba, Canada

The results of a discrete choice experiment (DCE) as a part of a survey among the urban riverbank residents on the Red River in Winnipeg, Manitoba, Canada, indicated that the risk of over-dike flooding, set at 2 ft above the 1997 flood water level, was a significant determinant of both voluntary and mandatory evacuation, compared to those set at the 1996 or 1997 levels. Mandatory evacuation was more preferred over voluntary evacuation when the likelihood of flooding was at its most severe, and the opposite relationship was the case when the likelihood was low. The notification time for evacuation, suggested as 1, 2, and 4 days, proved to be an insignificant attribute, whereas the respondents indicated significant preference for full flood compensation over an offer of either 80% or 90% flood relief, irrespective of the alternatives of voluntary or mandatory evacuation.

Risk, Schooling and the Choice of Seed Technology in Developing Countries: A Meta-Profit Function Approach

The determinants of rice seed variety choice are studied in a framework in which cultivator's variety specific profit, risk preferences, uncertainty and schooling affect variety choice. The econometric model takes the form of a simultaneous equation switching regimes model with random profit functions (the meta-profit function). Adoption of high yielding varieties in Indonesia is found to be positively associated with profitability, likelihood of flooding, quality of irrigation conditional on relative profit, and availability of credit, and negatively associated with likelihood of drought and land wealth. Schooling significantly affects variety specific profit and input demand but not variety choice. The spread of high yielding rice varieties (HYV's) has ushered in an era of agricultural transformation in Asia. In Indonesia, the adoption of these new seed varieties contributed importantly to a spectacular increase in Indonesia's rice production over the last decades-rice output grew at an annual rate of 4 percent during the 1970's and almost 6 percent in the 1980's. While experimental plots have demonstrated that under optimal conditions the mean yield of HYV rice far exceeds that of traditional varieties (TV's), many Asian cultivators do not plant HYV's. In Indonesia, the HYV revolution has been particularly slow to spread to many areas outside of Java and partly as a consequence the distribution of the gains derived from HYV's has been uneven. Accounting for differences in adoption rates is therefore of some interest. Differences in prices and fixed factors of production are one explanation for inter-farm differences in seed variety adoption. If cultivator's seed technology choices are the result of profit maximizing behavior, then varietal choice will depend on the determinants of profit: variable factor prices, the prices of (varietyspecific) output, and the level of fixed factors including the agro-climatic environment. Different profit functions exist for each variety, reflecting the differences in their biological technology. If seed variety choice is itself part of the cultivators profit-maximization problem, then there exists a single profit function-the metaprofit function-which treats variety choice as a variable input and from which all

The flooding of a powder — the importance of particle size distribution

This paper reviews the development of a new annular shear cell for the characterisation of aerated powders, and studies in detail the flooding phenomena for an alumina powder. Results have shown a large reduction in shear stress for small quantities of air entrainment and transition from normal Coulomb-solid flow to liquid-like flow at high shear rates. Addition of fine particles is shown to enhance these effects, thereby increasing the likelihood of flooding. Addition of particles of size 40 μm and below is shown to be the main factor. An increase of 10% of particles in this size range shows a similar shear response to that obtained with a sample of alumina known to have flooded, although smaller quantities also have a significant effect. Such low quantities of additional fines could occur due to segregation, resulting in pockets of material with a high chance of flooding under normal powder handling conditions.