Permanent (perennial) streams may not be labeled but are always shown with solid blue lines – intermittent streams (not shown above) are marked with dash-dot line – mark a perennial stream PS If the V or U shape in the contours points uphill, the topographic feature is a valley - streams often connect these points – mark an upward pointing U or V shape as UU or UV If the V or U shape in the contours points downhill, the feature is the nose of a hill – you will never see a stream here – mark a downward pointing V or U shape as DV or DU Contours never cross – if you see a line crossing contours, it is a stream or man-made feature such as a road – mark one of these crossings XC Sometimes you may see a loop with tic marks along the inside – this is a depression – mark one of these (a bit hard to find) with a D Visualizing in 3-D based on 2-D contours Delineate a small watershed - Delineate the watershed of the small stream at the point shown (i.e. draw a line that encloses all the area from which runoff will flow to the point): Model Watershed Features (If time permits) - For the following two topographic features, use Play-Doh to create an accurate 3-D model of the contours shown (note, this can now also be done using a digital elevation map and 3D printer): Tools: Pencil (NOT pen!) & a good eraser General method (practice makes perfect): Draw small arrows all over the map indicating the direction of maximum slope at each point Based on your arrows, locate the “drainage divides”, the topographic features such as hills and ridges that divide flow between adjacent streams – rough sketch in these boundaries first so you know the general shape of the watershed Now carefully sketch your way uphill from the point of interest, always perpendicular to contour lines For hills and other contour loops or bends, draw the boundary such that it divides these features in half Check that the watershed boundary is everywhere perpendicular to contour lines and does not cross any drainage divides
Permanent (perennial) streams may not be labeled but are always shown with solid blue lines – intermittent streams (not shown above) are marked with dash-dot line – mark a perennial stream PS If the V or U shape in the contours points uphill, the topographic feature is a valley - streams often connect these points – mark an upward pointing U or V shape as UU or UV If the V or U shape in the contours points downhill, the feature is the nose of a hill – you will never see a stream here – mark a downward pointing V or U shape as DV or DU Contours never cross – if you see a line crossing contours, it is a stream or man-made feature such as a road – mark one of these crossings XC Sometimes you may see a loop with tic marks along the inside – this is a depression – mark one of these (a bit hard to find) with a D Visualizing in 3-D based on 2-D contours Delineate a small watershed - Delineate the watershed of the small stream at the point shown (i.e. draw a line that encloses all the area from which runoff will flow to the point): Model Watershed Features (If time permits) - For the following two topographic features, use Play-Doh to create an accurate 3-D model of the contours shown (note, this can now also be done using a digital elevation map and 3D printer): Tools: Pencil (NOT pen!) & a good eraser General method (practice makes perfect): Draw small arrows all over the map indicating the direction of maximum slope at each point Based on your arrows, locate the “drainage divides”, the topographic features such as hills and ridges that divide flow between adjacent streams – rough sketch in these boundaries first so you know the general shape of the watershed Now carefully sketch your way uphill from the point of interest, always perpendicular to contour lines For hills and other contour loops or bends, draw the boundary such that it divides these features in half Check that the watershed boundary is everywhere perpendicular to contour lines and does not cross any drainage divides