the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Assessing flood hazard changes using climate model forcing
- 1School of Civil Engineering, The University of Queensland, Brisbane, QLD, Australia
- 2Science Economics and Insights Division, NSW Department of Planning and Environment, Australia
- 3School of Earth Atmospheric and Life Sciences, University of Wollongong, North Wollongong, NSW, Australia
- 1School of Civil Engineering, The University of Queensland, Brisbane, QLD, Australia
- 2Science Economics and Insights Division, NSW Department of Planning and Environment, Australia
- 3School of Earth Atmospheric and Life Sciences, University of Wollongong, North Wollongong, NSW, Australia
Abstract. A modelling framework for using regional climate projections to assess flooding hazard has been developed and applied to the Gwydir River (catchment 26,600 km2 and floodplain 8,100 km2), NSW, Australia. The model framework uses NSW and ACT Regional Climate Modelling version 1.5 projections combined with computationally efficient hydrologic and hydraulic models. While requiring model management and high-performance computing resources, the modelling framework successfully processed 18 regional climate projections into flood projections. Specifically, a six-member set of climate model combinations simulating a historical period (1950–2006) and a future period (2006–2100) under two global emission pathways (RCP4.5 and RP8.5) were used to predict flood depth and speed. In total, 1,470 continuous years were simulated at hourly time step. These flood (depth and speed) projections were analysed to assess the flood hazard changes under future climate scenarios by estimating changes in the annual probability of occurrence of a range of flood hazard classes. The six-member ensemble indicates flood hazard in the Gwydir Valley will decrease in the short, medium and long term. There are also cases within the ensemble which includes increases in all non-safe flood hazard classification while decreasing the safe flood hazard classification.
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David Patrick Callaghan and Michael G. Hughes
Status: final response (author comments only)
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RC1: 'Comment on nhess-2022-84', Jesper Neilsen, 09 May 2022
In interesting read Gents, and a lot of modelling Dave! I have a few points which would have made this an easier read for myself.
- The fact that the hydrology model was a flow routing model (no infiltration) could have perhaps been introduced earlier in the text and Figure 1.
- What is the "bias correction" in the regional models correcting and how big do these biases get?Â
- I see that LISFLOOD is used for very large domains. Perhaps a sentance or two explaining why the hydrologic model is still waranted would fit.
- Figure 2. The colours of the bathymetry and the associated colour bar have me believing that the catchment is stepped.
- Figure 2. What are the white patches? Could they be important?
- Line 278. The words "flow", "flow rate" and "discharge" are all used in this paper. Is discharge required?
- Line 231 and elsewhere. The word "constrain" is new to me in model development lingo.
- Figure 5 & 6. Wherever differences are plotted, I like the colourscheme to centre around white, with +ve value an increasing shade of red and -ve values a decreasing shade of blue, otherwise it is rather ambiguous.
- How many 1D structures were there in the original MIKE models and how big were they? I know we are doing comparisons here but we are also going to the effort of using a hydraulic modelÂ
Cheers,
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RC2: 'Comment on nhess-2022-84', Anonymous Referee #2, 09 May 2022
The manuscript describes a procedure for assessing flood hazard changes using climate model forcing.
The proposed methodology is interesting and the topic is surely appropriate for NHESS.
I am glad to suggest to publish the manuscript after some comments and suggestions to share with the authors to improve the manuscript.
General Comments
- It could be useful to better explain in the introduction the novelty of the paper since in literature there already are some articles that assess future flood hazard under climate changes scenario by using hydrologic and hydraulic models. In the present form the original contribution could be not so evident because it is not fully clear how the proposed methodology differ or increase its effectiveness from other studies on this topic.
- I suggest in the introduction to add more recent bibliography on this topic and information about what was already proposed in other countries, i.e.: 1) Ryu, J.-H.; Kim, J.-E.; Lee, J.-Y.; Kwon, H.-H.; Kim, T.-W. Estimating Optimal Design Frequency and Future Hydrological Risk in Local River Basins According to RCP Scenarios. Water, 2022, 14, 945, https://doi.org/10.3390/w14060945. 2) Shrestha, S.; W. Lohpaisankrit W. Flood hazard assessment under climate change scenarios in the Yang River Basin, Thailand. International Journal of Sustainable Built Environment, 2017, 6, 285–298, https://doi.org/10.1016/j.ijsbe.2016.09.006. 3) Janizadeh, S.; Pal, S.C.; Saha, A.; Chowdhuri, I.; Ahmadi, K.; Mirzaei, S.; Mosavi, A.H.; Tiefenbacher, J.P. Mapping the spatial and temporal variability of flood hazard affected by climate and land-use changes in the future. Journal of Environmental Management, 2021, 298, 113551, https://doi.org/10.1016/j.jenvman.2021.113551.
Specific Comments
- Lines 214-215: LISFLOOD was preferred to WCAD2D because it was found that the first model was faster than WCAD2D. Did you compare these model only for speed or also in terms of flood modelling results? In the latter case, did the test performed show significant differences?
- Lines 241-242: please explain how you derive a total physical time of 1470 years starting by the 18 projections included by NARCliM 1.5.
- Paragraph 2.6 (Lines 267-275): I don’t understand the criterium for selecting the epochs for flood hazard classification. How did you select as historical epoch the period 1980/1999, and as projected epochs the periods 2020/2039, 2050/2069 and 2080/2099 in the entire range 1950-2100?
Technical corrections
- Line 13 pag. 1: historical period (1950-2006) should be the same of that one reported in line 99 (1950-2005).
- Line 489 pag. 15: in the reference you miss probably the comma before 2009.
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David Patrick Callaghan and Michael G. Hughes
Data sets
Gwydir River hydraulic model results using regional climate projections Callaghan, David https://doi.org/10.48610/d7b1654
David Patrick Callaghan and Michael G. Hughes
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