The Collaborative International Dictionary of English v.0.48:

Batture \Bat`ture"\, n. [F., fr. battre to beat.]
   An elevated river bed or sea bed.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

BATTURE. An elevation of the bed of a river under the surface of the water;
but it is sometimes used to signify the same elevation when it has risen
above the surface. 6 M. R. 19, 216. The term battures is applied,
principally, to certain portions of the bed of the river Mississippi, which
are left dry when the water is low, and are covered again, either in whole
or in part by the annual swells. The word battures, in French, signifies
shoals or shallows, where there is not water enough for a ship to float.
They are otherwise called basses or brisans. Neuman's Marine Pocket Dict.;
Dict. de Trevoux.