Living with floods: victims' perceptions in Beijiang, Guangdong, China

This study revealed the collective values of the flood victims in the Beijiang area, Guangdong, China, as a result of a hazardous flood in 1994. The victims were sceptical of large flood-prevention engineering structures. They believed that flooding was unavoidable, but by extending support networks, applying hazard-resistant designs, and developing loss-sharing adjustments the disastrous effects of a flood could be mitigated. Seemingly, victims were prepared to live with floods and adopted functional adjustments to lessen flood impact.     

Pliocene aridity and Neogene landscape evolution recorded by a fluvial sediment system (Campaspe Formation) in northeast Queensland

Campaspe Formation, a surficial, fluviatile, sand-dominated unit, is extensively developed in the Charters Towers region of north Queensland where it covers an area of 11 000 km², overlying Paleozoic basement and erosional remnants of Paleogene Southern Cross Formation. In the northern part of its distribution, it is interlayered with, and overlain by, flows of Nulla Basalt. It is dated as mid-Pliocene, based on the 3.48 Ma age of the Myrrilumbing Flow interlayered with its upper part, an antiquity consistent with thin ferricrete locally developed at its surface. The formation defines the Campaspe Surface at an elevation of 200–440 m in the present landscape, falling gently from upland to the west towards the current channel of the Burdekin River. This surface is a relict alluvial plain little incised by easterly flowing tributaries of the Burdekin River and has survived, essentially intact, from the early Pliocene. Geometry of the formation is established from some 2000 mineral exploration drill holes and seismic profiling. It has an average thickness of some 60 m, reaching a maximum of over 200 m. It blankets a pre-existing, low relief landscape in which a basement ridge divides it into two sub-basins that mirror the present drainage. The formation consists of poorly sorted sandstone with minor conglomerate and siltstone, and contains paleosol horizons with associated calcrete. Matrix supported sandstone in the succession, indicates deposition in part from hyperconcentrated flows. Sandstones generally show poorly defined planar layering as typical of ephemeral overbank and terminal splay sediment bodies but beds with cross-lamination, indicating fluvial channel bed forms, are also present. They are characterised by pore-filling silt and mud, largely emplaced by post-depositional infiltration, such that the unit produces essentially no groundwater. Facies attributes are consistent with fluvial deposition in ephemeral, dry climate, distributary system, with inefficient cross-drainage discharge that induced aggradation, resulting in a substantial sediment body perched in the landscape. Framework grain compositions show the formation to be mineralogically mature, representing erosional debris derived from intense weathering in an earlier climatic regime recorded, at least in part, by duricrust developed in the fluviatile–lacustrine Southern Cross Formation of Paleogene age. Such duricrust intervals are now upstanding in the landscape, representing erosional remnants from inverted relief developed in a mid-Cenozoic, pluvial, landscape cycle. Paleoclimatic signature of the Campaspe Formation extends the record of Pliocene aridity, widely recognised elsewhere in Australia, to northeast Queensland. In large part the landscape of the Charters Towers district is relict from the early Pliocene and is in the process of readjusting to more pluvial climatic regimes. By implication, Pliocene aridity has, on a small scale, exerted a strong influence on the present physiography of Australian landscapes.     

FLOODPLAIN DELINEATION AND HOUSING SUBMARKETS: TWO CASE STUDIES

The effect of floodplain designation on the residential real estate market in two communities, Elmira, NY and Wilkes-Barre, PA, is presented. Discriminant analysis differentiates between floodplain and nonfloodplain housing, using as independent variables characteristics of the houses sold. Several varibles define submarkets, but they vary between the communities. Only selling price and lot size were significant for both communities. Distinct floodplain and nonfloodplain housing markets can be differentiated. This allows for isolation of socioeconomic and environmental variables that may contribute to the recovery of housing values following flooding or to the implementation of land use controls associated with floodplain designation.     

Floodplain hydrology of the Mekong Delta,Vietnam

The Mekong Delta is one of the largest and most intensively used estuaries in the world. Each year it witnesses widespread flooding which is both the basis of the livelihood for more than 17 million people but also the major hazard. Therefore, a thorough understanding of the hydrologic and hydraulic features is urgently required for various planning purposes. While the general causes and characteristics of the annual floods are understood, the inundation dynamics in the floodplains in Vietnam which are highly controlled by dikes and other control structures have not been investigated in depth. Especially, quantitative analyses are lacking, mainly due to scarce data about the inundation processes in the floodplains. Therefore, a comprehensive monitoring scheme for channel and floodplain inundation was established in a study area in the Plain of Reeds in the northeastern part of the Vietnamese Delta. This in situ data collection was complemented by a series of high‐resolution inundation maps derived from the TerraSAR‐X satellite for the flood seasons 2008 and 2009. Hence, the inundation dynamics in the channels and floodplains, and the interaction between channels and floodplains, could be quantified for the first time. The study identifies the strong human interference which is governed by flood protection levels, cropping patterns and communal water management. In addition, we examine the tidal influence on the inundation in various parts of the Delta, since it is expected that climate change‐induced sea level rise will increase the tidal contribution to floodplain inundation. Copyright © 2011 John Wiley & Sons, Ltd.     

Measuring the flow resistance of submerged grass

Through laboratory experiments conducted in a grass‐lined flume, the hydraulic resistance of grass is measured and quantified. For the grass examined, it is found that Manning's n value is greater than those recommended in well‐established texts such as Chow (1959. Open Channel Flow. McGraw‐Hill: Singapore), relatively lower than those predicted by n‐UR methods, but corresponds well with the value found from calibration studies of two‐ and three‐dimensional numerical models. The assumption of a uniform Manning's n value with flow depth, which is often made in numerical modelling, may be invalid depending on the relative submergence of the vegetation. Drag coefficients are evaluated for a method applicable to three‐dimensional numerical models. Further detailed experimental investigation and application of these approaches within a numerical modelling framework is now recommended. Copyright © 2002 John Wiley & Sons, Ltd.     

江苏地质灾害危险性区域评估与应用

为探究长江漫滩相软土的抗剪强度特征,采用静三轴仪对南京长江漫滩相原状软土进行一系列试验,探讨不同固结条件下漫滩相软土抗剪强度的变化规律。结果表明：当固结度在60%～100%时,增大初始有效围压可在一定程度上提高抗剪强度;在相同围压下,抗剪强度随固结度的增加均规律性增大。以完全固结时的抗剪强度值τf,100%为参考,给出不同固结度下τf对应的折减系数,同时分别给出内摩擦角和黏聚力随固结度的变化关系,为长江漫滩区建设工程地基设计与施工提供参考依据。     

Seasonal inundation patterns in two large savanna floodplains of South America: the Llanos de Moxos (Bolivia) and the Llanos del Orinoco (Venezuela and Colombia)

Inundation patterns in two of the largest savanna floodplains of South America were studied by analysis of the 37‐GHz polarization difference observed by the Scanning Multichannel Microwave Radiometer (Nimbus‐7 satellite). Flooded area was estimated at monthly intervals for January 1979 through to August 1987 using mixing models that account for the major landscape units with distinctive microwave emission characteristics. Results are presented separately for five subregions in each of the two floodplain regions to show the spatial as well as temporal variability in inundation patterns. The total area inundated during the 9 years varied between 2069 and 78 460 km² in the Llanos de Moxos (also spelled as Mojos; median area, 23 383 km²) and 1278 and 105 454 km² in the Llanos del Orinoco (median, 25 374 km²), not including the open‐water area of permanent lakes and river channels. The correlation between flooded area and river stage was used to extend the inundation records over a 30‐year period in the Moxos (1967–97) and a 58‐year period (1927–85) in the Orinoco. Interannual variability in inundation is greater in the Moxos than the Orinoco. Comparison of these data, however, with a previously published analysis of the Pantanal wetland shows that inundation patterns in these two floodplain regions are not as variable across years as they are in the Pantanal. Copyright © 2004 John Wiley & Sons, Ltd.     

The use of remotely sensed land cover to derive floodplain friction coefficients for flood inundation modelling

Remotely sensed land cover was used to generate spatially‐distributed friction coefficients for use in a two‐dimensional model of flood inundation. Such models are at the forefront of research into the prediction of river flooding. Standard practice, however, is to use single (static) friction coefficients on both the channel and floodplain, which are varied in a calibration procedure to provide a “best fit” to a known inundation extent. Spatially‐distributed friction provides a physically grounded estimate of friction that does not require fitting to a known inundation extent, but which can be fitted if desired. Remote sensing offers the opportunity to map these friction coefficients relatively straightforwardly and for low cost. Inundation was predicted using the LISFLOOD‐FP model for a reach on the River Nene, UK. Friction coefficients were produced from land cover predicted from Landsat TM imagery using both ML and fuzzy c‐means classifiction. The elevetion data used were from combined contour and differential global positioning system (GPS) elevation data. Predicted inundation using spatially‐distributed and static friction were compared. Spatially‐distributed friction had the greatest effect on the timing of flood inundation, but a small effect on predicted inundation extent. The results indicate that spatially‐distributed friction should be considered where the timing of initial flooding (e.g. for early warning) is important. Copyright © 2007 John Wiley & Sons, Ltd.