The changing nature and projection of floods across Australia

Gu, Xihui; Zhang, Qiang; Li, Jianfeng; Liu, Jianyu; Xu, Chong‐Yu; Sun, Peng

doi:10.1016/j.jhydrol.2020.124703

Cited by 23 publications

(11 citation statements)

References 74 publications

(73 reference statements)

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“…Analysis of trends in Australian flood data from 491 stations (Ishak et al, 2010) indicated that about 30 % showed trends in the annual maximum flood, with downward and upward trends in southern and northern parts of Australia respectively. Analyses of 780 unregulated catchments (Gu et al, 2020) revealed a similar geographical distribution of trends. Other studies have investigated trends in selected streamflow components in particular regions, such as the south-western region of Western Aus-tralia (Durrant and Byleveld, 2009;Petrone et al, 2010) and south-eastern Victoria (Tran and Ng, 2009).…”

mentioning

confidence: 75%

Regional significance of historical trends and step changes in Australian streamflow

Amirthanathan

Bari

Woldemeskel

et al. 2023

Hydrol. Earth Syst. Sci.

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Abstract. The Hydrologic Reference Stations is a network of 467 high-quality streamflow gauging stations across Australia that is developed and maintained by the Bureau of Meteorology as part of an ongoing responsibility under the Water Act 2007. The main objectives of the service are to observe and detect climate-driven changes in observed streamflow and to provide a quality-controlled dataset for research. We investigate trends and step changes in streamflow across Australia in data from all 467 streamflow gauging stations. Data from 30 to 69 years in duration ending in February 2019 were examined. We analysed data in terms of water-year totals and for the four seasons. The commencement of the water year varies across the country – mainly from February–March in the south to September–October in the north. We summarized our findings for each of the 12 drainage divisions defined by Australian Hydrological Geospatial Fabric (Geofabric) and for continental Australia as a whole. We used statistical tests to detect and analyse linear and step changes in seasonal and annual streamflow. Monotonic trends were detected using modified Mann–Kendall (MK) tests, including a variance correction approach (MK3), a block bootstrap approach (MK3bs) and a long-term persistence approach (MK4). A nonparametric Pettitt test was used for step-change detection and identification. The regional significance of these changes at the drainage division scale was analysed and synthesized using a Walker test. The Murray–Darling Basin, home to Australia's largest river system, showed statistically significant decreasing trends for the region with respect to the annual total and all four seasons. Drainage divisions in New South Wales, Victoria and Tasmania showed significant annual and seasonal decreasing trends. Similar results were found in south-western Western Australia, South Australia and north-eastern Queensland. There was no significant spatial pattern observed in central nor mid-west Western Australia, with one possible explanation for this being the sparse density of streamflow stations and/or the length of the datasets available. Only the Tanami–Timor Sea Coast drainage division in northern Australia showed increasing trends and step changes in annual and seasonal streamflow that were regionally significant. Most of the step changes occurred during 1970–1999. In the south-eastern part of Australia, the majority of the step changes occurred in the 1990s, before the onset of the “Millennium Drought”. Long-term monotonic trends in observed streamflow and its regional significance are consistent with observed changes in climate experienced across Australia. The findings of this study will assist water managers with long-term infrastructure planning and management of water resources under climate variability and change across Australia.

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confidence: 75%

Regional significance of historical trends and step changes in Australian streamflow

Amirthanathan

Bari

Woldemeskel

et al. 2023

Hydrol. Earth Syst. Sci.

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“…For a water rising process to be perceived by the fish, there must be a time lapse between two adjacent high water peaks 49 . Accordingly, the paired extremes [ ] identified in step (1) can be refined according to the amplitude and duration of the water falling process (in this study, the minimum falling amplitude is set to 10% of the initial rising amplitude, and the minimum falling duration is two days) 50 .…”

Section: Methodsmentioning

confidence: 99%

Identification and restoration of hydrological processes alteration during the fish spawning period

Yang

Zhao

Zhang³

et al. 2023

Sci Rep

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The hydrological processes play an important role in stimulating fish spawning behavior. Changes in the natural hydrological processes will alter the populations and distribution of fish, which may have a negative impact on the native aquatic organisms. The aim of this study is to identify the alteration of the water rising process during the fish spawning period and to construct an ecological flow optimization model to restore the water rising conditions for fish reproduction. The Mann–Kendall test and the sliding t-test were used to detect the mutation year of the mean daily flow data sets in the fish spawning period in each monitoring year. Then the data sets can be divided into pre-altered and post-altered periods. The water rising process was characterized by the water rising processes count, the duration, the daily flow increase rate, the date of the water rising process, and the initial water rising flow. The changes in hydrological processes in the middle reaches of the Yangtze River were investigated by comparing the post-altered and pre-altered characteristic parameters. Furthermore, we integrated the statistical values of the five characteristic parameters in pre-altered into an ecological flow optimization model to simulate the natural water rising processes for the spawning of the Four Major Chinese Carps (FMCC) and Chinese Sturgeon (CS). The analysis showed that after the hydrological mutation year, the duration and the initial water rising flow in the FMCC spawning season were increased, with hydrological alteration degrees of 63.10% and 70.16%, respectively; however, the daily flow increase rate was significantly decreased, with hydrological alteration of 86.50%. During the CS spawning season, the water rising processes count and the initial water rising flow were dramatically altered parameters, with hydrological alteration degrees of 50.86% and 83.27%, respectively. The former parameter increased, but the latter decreased significantly in the post-altered period. To induce the spawning activity of FMCC and CS, appropriate ecological flows and hydrological parameters were proposed. These results showed that during the spawning seasons of FMCC and CS, the hydrological processes of the middle reaches of the Yangtze River changed significantly. Therefore, ecological flow must be ensured through ecological operation of upstream reservoirs to provide suitable spawning conditions in target fish spawning grounds.

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“…In addition to these, one set of reports from the Australian Bureau of Meteorology was included (Assessment Reports). Using five GCMs from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and eight global hydrologic models, Gu et al (2020) projected changes up to the 1 in 50 AEP flood using the ISI-MIP trendpreserving bias correction method (Hempel et al, 2013). Frequent floods were projected to decrease across large parts of Australia, with some increases in the tropics.…”

Section: Systematic Reviewmentioning

confidence: 99%

A systematic review of climate change science relevant to Australian design flood estimation

Wasko,

Westra,

Nathan

et al. 2023

Preprint

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Abstract. In response to flood risk, design flood estimation is a cornerstone of planning, infrastructure design, setting of insurance premiums and emergency response planning. Under stationary assumptions, flood guidance and the methods used in design flood estimation are firmly established in practice and mature in their theoretical foundations, but under climate change, guidance is still in its infancy. Human-caused climate change is influencing factors that contribute to flood risk such as rainfall extremes and soil moisture, and that there is a need for updated flood guidance. However, a barrier to updating flood guidance is the translation of the science into practical application. For example, most science focuses on examining trends in annual maximum flood events, or the application of non-stationary flood frequency analysis. Although this science is valuable, in practice design flood estimation focuses on exceedance probabilities much rarer than annual maximum events, such as the 1 % annual exceedance probability event or even rarer, using rainfall-based procedures, at locations where there are little to no observations of streamflow. Here, we perform a systematic review to summarise the state-of-the-art understanding of the impact of climate change on design flood estimation in the Australian context, while also drawing on international literature. In addition, a meta-analysis, whereby results from multiple studies are combined, is conducted for extreme rainfall to provide quantitative estimates of possible future changes. This information is described in the context of contemporary design flood estimation practice, to facilitate the inclusion of climate science into design flood estimation practice.

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The changing nature and projection of floods across Australia

Cited by 23 publications

References 74 publications

Regional significance of historical trends and step changes in Australian streamflow

Regional significance of historical trends and step changes in Australian streamflow

Identification and restoration of hydrological processes alteration during the fish spawning period

A systematic review of climate change science relevant to Australian design flood estimation

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