Abstract. Thirty-six borehole temperature–depth profiles were analysed to reconstruct the ground surface temperature history (GSTH) of eastern Tasmania for the past 5 centuries. We used the singular value decomposition method to invert borehole temperatures to produce temperature histories. The quality of borehole data was classified as high or low based on model misfit. The quality of the borehole data was not dependent on topography or land use. Analysis reveals that three to five high-quality borehole temperature–depth profiles were adequate to reconstruct robust paleotemperature records from any area. Average GSTH reconstructed from Tasmanian boreholes shows temperature increases about 1.2 ± 0.2 °C during the past 5 centuries. Reconstructed temperatures were consistent with meteorological records and other proxy records from Tasmania during their period of overlap. Temperature changes were greatest around the north-east coast and decreased towards the centre of Tasmania. The extension of the East Australian Current (EAC) further south and its strengthening around the north-east coast of Tasmania over the past century was considered a prime driver of warmer temperatures observed in north-east Tasmania.
The paper presents the flood characterisation of the Haor region in the north-east of Bangladesh. The region consists of a system of Haors, each of which is a saucer-shaped depression and interconnected by a river system. A portion of the Haor area, known as the deeply flooded area, consisting of about 15 Haors, was chosen as the study area. A 1D2D model, with one-dimensional model for the rivers and a two-dimensional model for the Haors, was developed. Flood hydrograph characteristics such as the rising curve gradient, flood magnitude ratio (with respect to the average discharge) and time to peak were assessed for different river floods. Using these characteristics an integrated flood index (FI) was developed. The FI is an aggregated indicator based on the flood hydrograph characteristics and indicates the relative overall severity of a flood. The spatial and temporal variations of the index were investigated as well. The computed FI at different locations of the region and for different flood hazard frequencies provide a broad understanding of the flooding characteristics of the region. The developed methodology can also be applied to other river basins to analyse flooding risk provided some historical flood data are available.
Abstract. Flooding in the Haor region in the north-east of Bangladesh is presented in this paper. A haor is a saucershaped depression, which is used during the dry period (Dec to mid-May) for agriculture and as a fishery during the wet period (Jun-Nov). Pre-monsoon flooding till mid-May causes agricultural loss. The area is bordering India, and is fed by some flashy Indian catchments. The area is drained mainly by the Surma-Kushiyara river system. The terrain generally is flat and the flashy characteristics die out within a short distance from the border. Limited studies on the region, particularly with the help of numerical models, have been carried out in the past. Therefore, an objective of the current research was to set up numerical models capable of reasonably emulating the physical system. Such models could, for example, associate different gauges to the spatio-temporal variation of hydrodynamic variables and help in carrying out a systemic study on the flood propagation. A 1D2D model, with one-dimensional model for the rivers (based on MIKE 11 from DHI) and a two-dimensional model for the haors (based on MIKE 21 from DHI) were developed. In order to characterize flooding in the large area a flood index is proposed, which is computed based on the hydrograph characteristics such as the rising curve gradient, flood magnitude ratio and time to peak. The index was used in characterising flooding in the Haor region. In general, two groups of rivers were identified. The study enabled identifying the hot-spots in the study area with risks from flooding.
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