Using a Modified Simple Fill Model to Map Flood Inundation in the Darling-River Floodplain  

Authors / CoAuthors

Halas, L. | Magee, J. | Gow, L. | Lawrie, K. | Gibson, D.

Abstract

Inundation mapping is critical to improving our understanding of groundwater recharge processes in Australian floodplains. In this project, spatial extent, depth and frequency of flood waters were also critical inputs to MAR assessment and infrastructure design. Flood extent mapping can be undertaken in many ways including simple fill models reliant on elevation data or more complex numerical 1D or 2D models, both of which can be used to report on historical events and predict future scenarios. Remote sensing approaches are also used, although these are only capable of reporting on prior events. Simple fill models use a single known or estimated water level to produce a corresponding flood inundation extent, while numerical models account for and model the complex movement of water across the landscape in generating water levels and flood extents. However, numerical models are data intensive and somewhat subjective, being affected by input data, type of model and description of the river geometry in the model. In this study, insufficient information was available to develop a numerical model. Instead, a high-resolution LiDAR dataset was acquired over a 7,500 km2 area of the Darling River floodplain and combined with historic and real time river level gauge data to produce a simple fill model. A 20 m difference in floodplain elevation over the length of the river necessitated levelling of the LiDAR DEM to the Darling River floodplain. This was done by subtracting the interpolated floodplain elevation trend surface from the DEM, producing a de-trended floodplain surface. The levelled DEM surface was then adjusted to the water level as measured at the principal (Weir 32) river gauge station at the time of image acquisition. Flood extents were derived by elevation slicing of the new DEM surface to specified river levels; flood depth is an inverted version of the flood-extent grid. The approach proved successful in the central portion of the study area proximal to the river gauge station but overestimated and underestimated further south and north respectively. Calibration in these areas is hampered by a lack of survey and river gauge points, with possible approaches include generating trend surfaces for topographically discrete sections of the landscape and applying a simple fill to generate a continuous surface flow network.

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nonGeographicDataset

eCat Id

75753

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• External PublicationAbstract

( Theme )

• marine

Australian and New Zealand Standard Research Classification (ANZSRC)

• Geology

• Published_Internal

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2013-01-01T00:00:00

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Australian Government Security ClassificationSystem    

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geoscientificInformation

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Abstract prepared for submission to the International Association of Hydrogeologists (IAH).

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