india

You can refer the scheme of classification followed by GSI (Geological Survey of India) for its National Geomorphology Project.

River islands are classified considering size and stability criteria, though I could not find any size threshold for discriminating river islands from other bedforms. You can go through some of the papers:

1. https://www.researchgate.net/profile/Gail_Ashley/publication/273807682_Classification_of_Large-Scale_Subaqueous_Bedforms_A_New_Look_at_an_Old_Problem-SEPM_Bedforms_and_Bedding_Structures/links/55ef75ee08ae199d47c01413.pdf

2. https://www.researchgate.net/profile/Urs_Uehlinger/publication/227932997_Understanding_natural_patterns_and_processes_in_river_corridors_as_the_basis_for_effective_river_restoration/links/5447797b0cf2f14fb811f587.pdf

3. http://archives.datapages.com/data/sepm/journals/v47-50/data/048/048004/1321.htm?doi=10.1306%2F212F7676-2B24-11D7-8648000102C1865D

4. http://onlinelibrary.wiley.com/doi/10.1002/rrr.646/abstract

5. http://onlinelibrary.wiley.com/doi/10.1002/hyp.1173/abstract

If some of the papers may are not accessible from your place, ask me later, I will send you.

Article Classification of Large-Scale Subaqueous Bedforms: A New Loo...

Article Understanding Natural Patterns and Process in River Corridor...

Dear friend there are many classification systems, now depends on the type and theme addressed.

Nick

I think you can help work "morphometry of drainage basins" of I. Zavoianu, Elsevier, 1985; Developments in water science 20.

Dear Ananya, there are many types of river in different climatic condition. And they form different types of island as a response of the climatic condition . In depends upon the attitude of the study .