Notes: SAR in flood mapping

Flooding means the water presence in the ground surface below or above vegetation, or the presence of water in the surface which would not be in normal cases. SAR imagery has been used in studying, understanding and interpreting the study of the floods. The benefits of the SAR include the ability to collect images both day and night, and in any weather conditions and the appearance of the water surface appearing black compared to other surfaces. SAR signals can scatter in different ways based on whether the surface is smooth or rough, and can be affected based on the size of the object on the surface, their position in the surface and the numbers (or presence) of such structural surfaces. 

The practicality in SAR is the type of wavelength’s ability to penetrate the target (L-band having more penetration capability than C-band). L-band or P-band, in flooded areas with dense forest can be more interpretative compared to C-band (bands getting mixed between surfaces).

The advantage of SAR, being in the  ability of polarization, is used for determining the different physical properties of the object. The selection of the polarization depends on the place of flooding as well; different polarizations need varying analytical interpretations based on whether the flooding is in the open space, in the forest areas with presence of dense or sparse forest or vegetation or in the city areas with buildings or human habited places. The expert SAR users have selective choices and preferences in the selection of the polarizations based on the knowledge of the locations and their previous experiences; most selections based on the research.

Incidence Angle (depends on the swath) results high or less backscatter, and less incidence angle in surface scattering makes the surface appear more brighter. Such causes along with distortions can make interpretations of the flooded areas a difficult task (but selection of the proper data even more challenging). The needs are in understanding more of the backscattering mechanism in different flood surfaces.

Publicly available:

https://doi.org/10.1080/22797254.2020.1859340

https://doi.org/10.3311/FloodRisk2020.7.5

http://dx.doi.org/10.1109/JSTARS.2021.3083517

https://doi.org/10.1111/jfr3.12744

~posted as the content creation in the page.