If a major program is implemented to increase 

 water yield from the entire chaparral area, about 6 

 million acres could be converted to grass cover. The 

 increase in water yield would average about 1.2 

 million acre-feet each year. The median value, based 

 on measured run-off in Arizona, would be about 0.7 

 million acre-feet. 



Other prescriptions in the Southwest would, if 

 implemented, augment surface water supplies. One 

 practice which has received considerable study is the 

 eradication of phreatophyte vegetation along streams. 

 Under certain conditions, phreatophytes transpire up 

 to 6 or 7 acre-feet of water per acre of surface area.^' 

 Eradicating deep-rooted plants and substituting shal- 

 lower rooted species in areas where water tables are a 

 few feet below the surface can save part of this water. 

 To be effective, the cleared area must be mowed, 

 plowed, or sprayed with herbicides periodically to 

 prevent the deep-rooted vegetation from recapturing 

 the site. 



It is estimated that an intensive phreatophyte erad- 

 ication and control program applied on 8 percent of 

 the areas occupied by phreatophytic vegetation would 

 save 0.9 million acre-feet of water each year.^* The 

 cost of clearing, control, and maintenance was esti- 

 mated at SI 4.00 annually for each acre-foot of water 

 produced. 



The opportunity to increase water yield from areas 

 supporting sagebrush and pinyon-juniper is minimal 

 because of the dry climate. 



Estimates of increased water supplies presented 

 here are based on the expected difference in runoff 

 between no forest management and specific manage- 

 ment for water yield increases. The values presented 

 in table 7.15 through 7.17 should be considered as the 

 upper limits which could theoretically be achieved 

 and not the expected changes which will be produced 

 and sustained through planned environmentally 

 acceptable multiple-use management over the next 

 half century. 



Flood Damage Management 



The Department of the Army and the Department 

 of Agriculture have active flood control, flood pre- 

 vention, and watershed protection. Expenditures on 

 structural measures such as dams, levees, and chan- 

 nels installed under these programs have averaged 

 over $600 million per year over the last 10 years. 

 There are, of course, many additional opportunities 



55 Horton, Jerome S., and C. J. Campbell. Management of 

 phreatophyte and riparian vegetation for maximum multiple use 

 values. U.S. Department of Agriculture, Forest Service, Research 

 Paper RM-117, 23 p. 1974. 



56 Reigner, Maloney, and Dunford, op. cii. 



for flood control structures. For example, a recent 

 analysis" indicated that it should be possible to 

 reduce annual losses by at least 20 percent if these 

 structures could be built rapidly and cheaply enough. 



In recent years, increasing emphasis has been 

 placed on the use of nonstructural measures to miti- 

 gate flood damage. These nonstructural measures 

 include flood insurance; flood-proofing of structures; 

 flood plain regulation; acquisition of flood plain 

 lands for recreation, fish and wildlife, and other 

 public purposes; public information programs; tax 

 incentives; and improved forecasting and warning 

 systems. 



In many cases, a combination of structural and 

 nonstructural measures will likely be most effective. 

 Programs that are developed should give full con- 

 sideration to the specific situation being faced, and 

 the attendant decisions should be focused on meeting 

 specified objectives at the lowest possible cost. 



A land treatment program should be part of any 

 flood management effort. Proper watershed protec- 

 tion helps reduce flooding by reducing or delaying the 

 sedimentation of flood-retarding structures and 

 stream channels. Land treatment can also affect the 

 amount and rate of flood run-off and can comple- 

 ment other structural and nonstructural measures. 



One opportunity to reduce flood damages is to 

 remove floatable debris from flood plains. This is 

 especially true for floods with recurrence intervals of 

 up to 25 years, where most debris is lying loose in the 

 flood plain before the flood occurs. For floods with 

 longer return periods, much of the debris is made 

 available to the flood, for example by the water 

 undercutting banks, so large trees and brush are 

 dropped into the floodwater and carried downstream. 

 Debris left by logging, land clearing for development, 

 construction, or other services could be removed 

 through the various manpower programs of public 

 service groups. Increased technical and financial assis- 

 tance to owners of private forest and range land also 

 could reduce the amount of floatable debris. More 

 importantly, education of groups or industries that 

 create this debris could prevent much of the debris 

 from accumulating. 



Pollution Control — Point Source 



The strategy for controlling point source pollution 

 has undergone a major change since the late 1960's 

 when large scale pollution control efforts first began. 

 The initial efforts in controlling pollution from muni- 

 cipahties and industries were based on maintaining 



5' White. Gilbert F.. and J. Eugene Hass. Assessment of research 

 on natural hazards. The MIT Press, Cambridge. Massachusetts. 

 1977. 



314 



