Topographic maps have lines called contour lines. These joint points of equal height above sea level. The further apart the lines are, the gentler the slope. The difference in height between each contour line is called the contour interval.The patterns created by contour lines makes some landforms easily identifiable because each landform feature has quite a distinctive look.You need to be familiar with a few key contour patterns such as hills, valleys, saddles, streams and cliffs so you can interpret a topographic map.