<tr>
      <th>retainAreaProportion</th>
      <td><p>Boolean value. If TRUE retains a variable in
the resulting SpatialPolygonsDataFrame containing the proportion of the
original area within the catchment area (Default = FALSE).</p></td>
    </tr>
    <tr>
      <th>dissolve</th>
      <td><p>Boolean value. If TRUE collapses the underlying zones
within the catchment area into a single region with statistics for the
whole catchment area.</p></td>
    </tr>
    <tr>
      <th>quadsegs</th>
      <td><p>Numbe