Estimating the Water Requirements for Plants of Floodplain Wetlands

Appendix 1:Remote SensingChoice of applicationRemote sensing has several potential applications when estimating thewater requirements of floodplain wetlands. Examples are: to compile aninundation map for a depth measurements; to compile a time series oran event-series of inundation; to map vegetation; to monitor vegetation.Applications using radar still under development and not fully ready forroutine use include: to define the phreatic surface; to characterise thesub-surface sediments; to recognise individual species.A summary of costs, technical specifications regarding space-borne andaerial sensors, coverage dates, overpass frequency (satellite imagery)and scene size are given in Tables A1 – 1 and A1 – 2. For acomprehensive review, and pointers to future applications, consult:“Evaluation of the feasibility of remote sensing for monitoringnational state of the environment indicators” by J. Wallace and N.Campbell 1999. Australia: State of the Environment Technical PaperSeries (Environmental Indicators), Department of the Environment,Canberra.Choice of application is usually determined by size of study area,resources available, intended use and availability. As a general guide,final choice depends on size and scale: applications most suitable forsmall wetlands or individual billabongs are generally inappropriate,cumbersome or even too expensive for large floodplain wetlands: andvice versa. Therefore while it is valid to copy what has been doneelsewhere, this should be done with caution, making sure it suits thestudy area.Inundation mappingBoth aerial photography and satellite imagery have been used forinundation mapping in Australia; the use of radar is just beginning. Forlarge areas it is more cost-effective to use historical satellite imagery thanto obtain historical colour photographs (if available). The reverse is truefor small wetland areas, where aerial photography, preferably colour ifavailable, is most suitable as it gives better resolution.Current practice regarding inundation mapping in Australia has been touse historical satellite images to build up an incremental sequence.Availability of historical material (Table A1 – 2) and the high variability ofmost Australian rivers means the source material is effectivelyconstrained to Landsat TM and/or Landsat MSS; sometimes to Spotimagery if lucky with an appropriate flood sequence in the last 13+years. Examples of this approach are given in Note 31.An alternative to using historical imagery is to commission airbornehyperspectral or radar imagery, and build a sequence by following oneAppendix 1: Remote Sensing 101