In this example, the seismic acquisition project went on standby for several months while the river levels where deemed too high based on irregular visual observations. With better access to relevant flood extent information, a contingency plan for operations could have been initiated and in the very least a confident and considered decision made when operations could resume again as the flood waters recede.
The SRTM data set is a very useful product, but should be used with caution in forested regions. The use of C-band InSAR also means penetration of forest canopy is poor which can result in vertical errors of up to 20m in tree covered regions. All of this needs to be understood before utilising SRTM data for survey planning.
One important benefit of the SRTM data set is that it is freely available and has global coverage. Aerial surveys were too costly to be considered for this project. Elevation products such as Elevation 8 and Elevation 12 may provide operational benefit, but at increased cost, and in this case coverage was not available off the shelf for the area of interest.
In addition to a more detailed DTM surface model, accurate temporal river level and flood extent observation data would have allowed for a much more flexible approach to river monitoring and flood planning. River height gauges would be impractical in such an environment and prohibitively expensive to set up in advance of planning. The use of radar and optical EO to observe the extent of flooding in near-real time would provide valuable information for planning and modification of survey activities. Products are potentially availability at low cost, for example if products are based on Sentinel-1, Sentinel-2, Landsat-8, or other low cost “persistent monitoring” systems.
Overall, it is recognized that the combination of a “bare earth” DTM and relevant time stamped river elevations would enable effective flood extent area analysis. Coupled with observations of an area in near-real time, seismic logistics planning could be more responsive to environmental conditions.