<Ul> <Li> The rule of Vs: sharp - pointed vees usually are in stream valleys, with the drainage channel passing through the point of the vee, with the vee pointing upstream . This is a consequence of erosion . </Li> <Li> The rule of Os: closed loops are normally uphill on the inside and downhill on the outside, and the innermost loop is the highest area . If a loop instead represents a depression, some maps note this by short lines radiating from the inside of the loop, called "hachures". </Li> <Li> Spacing of contours: close contours indicate a steep slope; distant contours a shallow slope . Two or more contour lines merging indicates a cliff . By counting the number of contours that cross a segment of a stream, the stream gradient can be approximated . </Li> </Ul> <Li> The rule of Vs: sharp - pointed vees usually are in stream valleys, with the drainage channel passing through the point of the vee, with the vee pointing upstream . This is a consequence of erosion . </Li> <Li> The rule of Os: closed loops are normally uphill on the inside and downhill on the outside, and the innermost loop is the highest area . If a loop instead represents a depression, some maps note this by short lines radiating from the inside of the loop, called "hachures". </Li> <Li> Spacing of contours: close contours indicate a steep slope; distant contours a shallow slope . Two or more contour lines merging indicates a cliff . By counting the number of contours that cross a segment of a stream, the stream gradient can be approximated . </Li>

What colour are contour lines on a topographic map