Kalyani Vartak and I have a book chapter on 'Migration and Caste' that came out a few months back. A very short thread with link to the article in the end. We review around 100 studies on this subject and our own work and propose a framework, as shown in this chart. 
At the macro level, as observed in previous studies (esp. by @priyadeshingkar @ArjanDevDebate ), there is a broad positive relationship between caste rank and out-migration in longer duration migration streams and inverse relationship in shorter duration migration streams.
This feature + Historically, permanent migrations out of the villages to the cities have been dominated by the 'General' category=> Urbanization rates among General category, therefore, nearly double that of OBC, SC [Urban definition matters for this number but not ranking].
While place in caste hierarchy can strongly condition the nature of out-migration, interestingly, instances of the reverse are also found- of migration and remittances leading to a change in caste identity and hierarchy (eg. Kanbi to Patidar movement in early 20th c).
The article also looks at migration+caste and gender, diaspora, remittances, resistances and inferences from Kalyani's remarkable field work in a Konkan vilage, for her PhD thesis.
Our conclusion: "Migration, on balance, we argue, is an important pathway out of the pernicious aspects of the caste system as a means of resistance, as a way of earning anonymity and as a generator of economic and social remittances."
Study can be found on this link (Scroll down or search for 'caste' on that page).
sites.google.com/site/chinmaytu…
sites.google.com/site/chinmaytu…
