Description: <DIV STYLE="text-align:Left;font-size:12pt"><P><SPAN>Historic active channel swath mapping informs the extent to which the modern floodplain has been swept by the migrating river channel. Both the Waikaia and Mataura have the propensity for lateral change and adjustment. Classically in meandering reaches, this adjustment involves bend development, migration and cutoff. In more wandering and braided reaches, lateral adjustment also entails avulsion, or rapid switching of the channel. The floodplain that has been swept by these processes can be considered that which is most active, readily re-worked and most likely and most regularly flooded. </SPAN></P><P><SPAN /></P><P><SPAN>Swath mapping was produced by staff at Land River Sea (LRS) and Environment Southland for the Mataura and lower Waikaia by mapping the boundaries of the active channel. The active channel is defined as that part of the river corridor comprising wetted channel and bare or lightly vegetated (active) bar surfaces.</SPAN><SPAN> </SPAN><SPAN> These features were mapped using available aerial photo imagery from LINZ and Retrolens. LRS supplied rectified Retrolens imagery. </SPAN></P><P><SPAN /></P><P><SPAN>These channel swaths are necessarily approximate due to variable quality of aerial imagery and the challenges of mapping in stong shadow and along the line of densely vegetated banks, but nevertheless give a clear indication of the most active portion of the floodplain, which is used to define the minimal extent of floodplain engagement (along with floodbanks). </SPAN></P></DIV>