The first maps that are needed are the New Haven and Mount Carmel Quadrangles of the United States Geological Survey topographic maps. In order to become familiar with the maps and their accuracy, each student will find his or her home and school. (An optional exercise for advanced students would be to express these locations as longitude and latitude and understand how these angular measurements are used to locate points on the globe.) Then the idea of scale is introduced. These maps are 1:24,000, or every distance is really 24,000 times as far as it is on the map. This can be demonstrated by taking the length that represents a mile or a kilometer on the map scale and multiplying it by 24,000. Using either the multiplying length method or the scale each student will determine the distance from home to a point of interest. In the course of this exercise students will become familiar with the main symbols used in the map and the use of the key, which is available separately.
The next aspect of map reading is the contour lines and how they define the shape of the land. To understand this each student will draw a cross section of a different point on the brook, including some of the places where the field visits were made. An enlargement of the topo maps would be useful for this exercise. A straight edge should be positioned roughly perpendicular to the brook at regular intervals, and the contour lines marked where they cross the straight edge (paper). The results should be transferred to another paper. If one cross section is made with the elevations to scale, the students will see that at the scale of these maps, there is very little vertical change. If the vertical scale is exaggerated it will present a more obvious idea of the shape of the watershed. An exaggeration of 3:1 (each vertical distance is three times the scale of each horizontal distance) is used in making raised relief maps and could be used here (see illustration).
If these are done at regular intervals they will be useful for the next exercise. The contour drawings should extend beyond the nearest high points. They then will give students a very clear picture of watershed or drainage basin. They will see which way the rain will run off. Information from the depth to bedrock map and contour map of the bedrock surface could be added to help visualize underground flow. The similarity of the bedrock and surface contours and the evenness of the depth to bedrock will help students understand that the irregular surface of the land follows closely the surface of the bedrock underneath.
After the cross sections are done, students will be able to draw the outline of the watershed on the map.
Next a similar exercise should be done for the length of the brook from the highest ground near Mountain Road in Hamden to the Long Island Sound. The part from the beginning through the Nature Center should be done in greater detail than the rest. These two exercises should provide a very good feel of the topography of the area under study and prepare the students to see how this area has changed in the last 200 million years.
