The Collaborative International Dictionary of English v.0.48:

Imbank \Im*bank"\, v. t. [imp. & p. p. Imbanked; p. pr. & vb.
   n. Imbanking.] [Pref. im- in + bank. Cf. Embank.]
   To inclose or defend with a bank or banks. See Embank.
   [1913 Webster]