For geomorphological mapping or for that matter a geological mapping, moderate resolution multi-spectral imagery may not be very useful if used in isolation. Usually it works better in combination with a colour-shaded DEM for example, in combination with a pan-sharpened imagery and an anaglyph image. I've attached all of the mentioned imagery as an example for you to weigh the difference and the significance of each in relation to the objective. Usually, I found that a colour-shaded topographic image is an excellent starting point to map geomorphological units which may not be visible/obvious at all in a Landsat ETM multi-spectral imagery. In the attached example you can quite clearly make out the alluvial fans which are at the base of the Lower Himalayas on which Dehradhun city is situated, which is otherwise not so apparent in the ETM multi-spectral imagery. With some proficiency you can even distinguish the relative ages of the alluvial fans which are found in between the Siwalik Range and the Lower Himalayas. You can also see them in the Indogangetic plains. The river channels are easily discernible in the hill-shaded image and the variations in the intricate drainage patterns are conspicuous enough to pinpoint the differences in underlying lithology. Often with multi-spectral colour composites the terrain may not be highlighted because of the presence of vegetation, anthropogenic borders etc. Have a look at the color composite ETM where a clear boundary (human made) is identified along the south face of the Siwalik Range, whereas if you compare the same location in the color-shaded DEM, you will not find it. These are only some of the advantages of using a colour-shaded DEM in conjunction with a colour composite multi-spectral imagery for geomorphological mapping where the terrain information is more valuable than a land cover. For geological mapping too, these data sources are superlative authorities, wherein anticlines, synclines, strike-slip faults, lineaments, flatirons (indicators of bedding planes) and many other geological features are observed with marked distinction. Therefore, I think the key to a first-rate geomorphological mapping is a blend of various data sources. I'm not sure what is the scale of your study area, nevertheless I believe ETM/OLI from Landsat together with a DEM can be a good starting point for a fine and direct geomorphological mapping. My views are open for criticism and discussion.

For geomorphological mapping or for that matter a geological mapping, moderate resolution multi-spectral imagery may not be very useful if used in isolation. Usually it works better in combination with a colour-shaded DEM for example, in combination with a pan-sharpened imagery and an anaglyph image. I've attached all of the mentioned imagery as an example for you to weigh the difference and the significance of each in relation to the objective. Usually, I found that a colour-shaded topographic image is an excellent starting point to map geomorphological units which may not be visible/obvious at all in a Landsat ETM multi-spectral imagery. In the attached example you can quite clearly make out the alluvial fans which are at the base of the Lower Himalayas on which Dehradhun city is situated, which is otherwise not so apparent in the ETM multi-spectral imagery. With some proficiency you can even distinguish the relative ages of the alluvial fans which are found in between the Siwalik Range and the Lower Himalayas. You can also see them in the Indogangetic plains. The river channels are easily discernible in the hill-shaded image and the variations in the intricate drainage patterns are conspicuous enough to pinpoint the differences in underlying lithology. Often with multi-spectral colour composites the terrain may not be highlighted because of the presence of vegetation, anthropogenic borders etc. Have a look at the color composite ETM where a clear boundary (human made) is identified along the south face of the Siwalik Range, whereas if you compare the same location in the color-shaded DEM, you will not find it. These are only some of the advantages of using a colour-shaded DEM in conjunction with a colour composite multi-spectral imagery for geomorphological mapping where the terrain information is more valuable than a land cover. For geological mapping too, these data sources are superlative authorities, wherein anticlines, synclines, strike-slip faults, lineaments, flatirons (indicators of bedding planes) and many other geological features are observed with marked distinction. Therefore, I think the key to a first-rate geomorphological mapping is a blend of various data sources. I'm not sure what is the scale of your study area, nevertheless I believe ETM/OLI from Landsat together with a DEM can be a good starting point for a fine and direct geomorphological mapping. My views are open for criticism and discussion.

Use of high resolution imagery would be better for this kind of a study along with hill shaded DEM as mentioned in the previous answer. Cartosat-1/2 stereo data can also be used to generate DEM by using photogrammetric processing.

Thank you all ... for comments. 

I think landsat data are not designed for geomorphological purposes. Its preferable to use DEM data for such studies as told above.

regards

I totally agree with Satej Panditrao and Khatir Benhanifia.

DEM it's the better solution for your work.

I totally agree with James