Correct direction of hydrography
Control of heights of first and last points of the object is made. If the last point higher than the first - object turns round.
Priority of methods for determining the height of the point:
1. From the description of metrics (in the case of 3D metrics).
2. From matrix of heights.
3. By processing the surrounded objects with 3D metrics or characteristic Absolute height.
The third method is the most durable. Therefore it is recommended before performing this procedure to add (or create in the absence) matrix of heights of relief into a document.