OCR Text |
Show be obtained in the efficient execution of water development progra maps portray, by means of accepted symbols and nomenclature, man- made features which comprise the land surface. In view of the fact that less than 20 percent of the United St£ mapped for water development purposes, the serious need for Ion and positive action in the production of topographic maps become Prior to field investigations, an office study of drainage basin c be made with facility by the use of a topographic map. These c slope, probable runoff, length and density of drainage channels, elevations over the entire area. The determined drainage characteristics lead directly to a k factors affecting flood and flood control. Since they are related t( precipitation and snow storage can be partially forecast from data map. Sites can be chosen for measuring flood discharge. With the t points at hand which were established for the purpose of map prep determinations of flood crest stages and flood crest profiles can be ma< A topographic map contains the essential information needec percentage relationship between total land and water area. This primary consideration in the study of the question of evaporation. With the map as a base, land use findings can be plotted, with knowledge of vegetative cover and precipitation, assist in t erosion characteristics. |