As per para 12 of AS 6 combination of different methods (different accounting policies) can be adopted by the enterprise as per para 12 of AS 6 . which is reproduced below
12. There are several methods of allocating depreciation over the useful
life of the assets. Those most commonly employed in industrial and
commercial enterprises are the straightline method and the reducing balance
Depreciation Accounting
method. The management of a business selects the most appropriate
method(s) ( which indicates that more than one method can be adopted ) based on various important factors e.g., (i) type of asset, (ii) the
nature of the use of such asset and (iii) circumstances prevailing in the
business. A combination of more than one method is sometimes used. In
respect of depreciable assets which do not have material value, depreciation
is often allocated fully in the accounting period in which they are acquired.
Finally the depreciation policy which you have adopted for branch assets should be in consistent manner.