The Collaborative International Dictionary of English v.0.48:

Embank \Em*bank"\, v. t. [imp. & p. p. Embanked; p. pr. & vb.
   n. Embanking.] [Pref. em- + bank. Cf. Imbank.]
   To throw up a bank so as to confine or to defend; to protect
   by a bank of earth or stone.
   [1913 Webster]

WordNet (r) 3.0 (2006):

embank
    v 1: enclose with banks, as for support or protection; "The
         river was embanked with a dyke"