What do you mean with LE8?

LE 8 is a LANDSAT 8 satellite which was launched by American Earth observation satellite launched on February 11, 2013. It has total 11 band.

You can refer following

http://landsat.gsfc.nasa.gov/pdf_archive/20101119_LDCMbrochure.pdf

Dear Sanjeev,

Any satellite data which has z-values (or elevation values) is helpful in estimating height or depth of any landform or feature. Once I checked Landsat 8 data and it was not showing elevation values (for my study area in Ganga plain). So, with that particular piece of data, I could not get height values of features. But, as some of the scenes of Landsat 7 (may be, some scenes of LS8 also) show elevation values, for those areas, height or depth estimation with the data is possible (accuracy of which will depend on the accuracy of z values recorded in the data)

Dear Sanjeev,

Spectral reflectance in 'red, green and blue' can be used to measure the bathymetry in clear water bodies. In rivers, however, spectral reflectance is also strongly affected by sediment concentrations, sediment colour, algal blooms, and dissolved organic matter. More information can be found in e.g. various publications by Arnold G. Dekker (https://www.researchgate.net/profile/Arnold_Dekker).  

In cases where the river water is clear enough to see the bottom (several metres), aerial photgraphs are commonly used with good results. (e.g. Lane, S.N., Widdison, P.E., Thomas, R.E., Ashworth, P.J., Best, J.L., Lunt, I.A., Smith, G.H.S. et Simpson, C.J. (2010). Quantification of braided river channel change using archival digital image analysis. EARTH SURFACE PROCESSES AND LANDFORMS, 35(8): 971-985. Doi:10.1002/esp.2015).

In both cases, having decent 'ground truth' is essential. Given the large pixel size of landsat, I don't think there are a lot of rivers that are 1) wide enough, 2) shallow / clear enough to make landsat the ideal platform. But imagery collected with Unmanned Aerial Vehicles is becoming very affordable these days...

Good luck!