Lab 7 Answer Sheet

Fnu Saira GEO 221 Environmental Geology Lab 7 Answer Sheet Exercise 1 – Drainage Basins (6 points – 1 point per question) 1. There are greater expanses of level territory in the north, particularly north of the Mogollon Rim National Park boundary, and much more flat land in the south, which starts off extremely steep and becomes more gradual as you descend towards the Tonto Fish Hatchery. 2. The division seems to occur at Mogollon Rim. 3. Complete the following table. A. Streams North of the Mogollon Rim B. Streams South of the Mogollon Rim Name Gradient (ft/mile) Name Gradient (ft/mile) West Leonard Canyon 96 Big Canyon Creek 405 Middle Leonard Canyon 167 Dick Williams Creek 639 East Leonard Canyon 132 Horton Creek 333 Turkey Canyon 132 Doubtful Canyon 521 Beaver Canyon 81 Spring Creek 568 Bear Canyon 125 See Canyon 318 Average Gradient North of the Mogollon Rim 122 Average Gradient South of the Mogollon Rim 464 4. There is a lot more level gradient to the north of Mogollon Rim. There is more flexibility and a greater separation between contour lines. Regarding the area south of the Mogollon Rim, the flow starts at the contour line, and Tonto Spring is located at the top of the cliff face. Because of their proximity, the gradient is quite high. 5. 6. Exercise 2 – Stream Erosion and Base Level (4 points – 1 point per question) 7. 8. 9. Page 1 of 3

Fnu Saira GEO 221 Environmental Geology Lab 7 Answer Sheet 10 Exercise 3: Flood Discharge, Recurrence Intervals, and the 100 Year Flood (15 points – question 11 worth 4 points, all other questions worth 1 point) Mercer Creek – Data Set 1 Mercer Creek – Data Set 2 Year Peak Flood Discharge Ran k Recurrence interval Year Peak Flood Discharge Ran k Recurrence Interval 1957 180 1979 518 1958 238 1980 414 1959 220 1981 670 1960 210 1982 612 1961 192 1983 404 1962 168 1984 353 1963 150 1985 832 1964 224 1986 504 1965 193 1987 331 1966 187 1988 228 1967 254 1989 664 Green River – Data Set 1 Green River – Data Set 2 Year Peak Flood Discharge Ran k Recurrence interval Year Peak Flood Discharge Ran k Recurrence Interval 1941 9310 1976 4490 1942 10900 1977 9920 1943 12900 1978 6450 1944 13600 1979 8730 1945 12800 1980 5200 1946 22000 1981 9300 1947 9990 1982 10800 1948 6420 1983 9140 Page 2 of 3