Dear Amit,

It is very unlikely that optical remote sensing will be appropriate to estimate the bathymetry of a river such as the Brahmaputra, especially in the presence of heavy sediment loads.

Whatever apparent positive results you may already have witnessed were likely obtained by chance. The penetration of sunlight in water is highly dependent on the wavelength, with light in the blue region being the only one that penetrates to some appreciable extent. And this is specifically the range that would be strongly absorbed by the sediments. Optical remote sensing can achieve many things, but that is not one of them. You will be better off adopting other (well-known) technologies for that purpose, such as sonar sounding, for that purpose.

This being said, it is also essential to understand what is your accuracy requirement: if the quality of the result is irrelevant, then any method will do!

Best regards, Michel.

Dear Amit,

It is very unlikely that optical remote sensing will be appropriate to estimate the bathymetry of a river such as the Brahmaputra, especially in the presence of heavy sediment loads.

Whatever apparent positive results you may already have witnessed were likely obtained by chance. The penetration of sunlight in water is highly dependent on the wavelength, with light in the blue region being the only one that penetrates to some appreciable extent. And this is specifically the range that would be strongly absorbed by the sediments. Optical remote sensing can achieve many things, but that is not one of them. You will be better off adopting other (well-known) technologies for that purpose, such as sonar sounding, for that purpose.

This being said, it is also essential to understand what is your accuracy requirement: if the quality of the result is irrelevant, then any method will do!

Best regards, Michel.

Dear Amit 

Optical remote sensing have some limitation. you can use Lidar based technology such as SONAR for bathymetry survey.  GPR survey also perform for such investigation.

Dear Amit,

Optical remote sensing aided with DEM'S can help you to some extend, but it depends what analysis you have to do. you can also use elevation from Google earth where you can plot a river profile.  its very simple to check your errors as the elevation profile with higher accuracy is automatically generated for your assistance i have attached a pic of Google earth where i digitized a small area of Jhelum river J&K and its elevation profile is visible to you.

hope this will help you to carry out your analysis. 

wish you success 

Best regards 

Dear Amit,

                       Determining the bathymetry of ocean using optical remote sensing  to certain extend(meters) is proved  by various method(Literature). It is understandable that river is coupled with sediments etc., But you can use those methods and compare the results with In-Situ data.

Amit,

I agree with what Michel has to say about the use of optical imaging systems to get bathymetry in both coastal and river waters when suspended sediment is present.  I used satellite and airborne optical imaging to extract information about a coral reef in Hawaii; with the VERY CLEAR coastal waters the optical images allowed us to see down to about 30 or so meters.  This was only because it was so clear; when the turbidity increased due either to coastal flooding or trade winds resuspended the near shore sediments we could not see the bottom at even 1 meter.  For bathymetry we used an airborne lidar system with a blue-green and nir laser and were able to extract information down to about 45 meters (see the attached file for an example of the data). 

I also did some work on the Salton Sea in the southwestern United States (extreme southern California) to extract information related to both bathymetry and bottom sediments.  This large lake is turbid enough most of the time that there is very little penetration of the water in the visible bands (of course, the nir bands hardly penetrate at all in most cases).  We used an acoustic dual-frequency profiling system on a boat to get bathy information along the trackline and then did surface interpolation on these data to get a bathy DEM (along with sediment information from the acoustic returns).  Part of the investigation included taking data collected from a previous survey and doing some change detection on the two bathy data sets to generate a map showing where erosion or build up had occurred (see the 2nd attached file below for an example of this)

I say all this to high light the fact that for our work optical systems in waters with moderate to high amounts of turbidity just will not work for extracting bottom information related to either sediment types/characteristics and/or bathy information.

Pat