The amount of storm water runoff depends on a great number of factors. Some of these factors are reasonably fixed and subject to accurate determination, such as watershed size and shape, ground slope and natural ponding. Others are seasonably variable, such as frozen soil, soil moisture condition, evaporation, or transpiration. Still others vary by land use, such as type of ground cover and impervious areas or method of cultivation. Finally, rainfall is extremely variable as to seasonal conditions and other variable factors. Despite the indeterminate nature of these factors, methods for obtaining useful information about storm water runoff have been developed. One of the four methods described in Urban Hydrology for Small Watersheds, Technical Release Number 55, by the Soil Conservation Service of the United States Department of Agriculture and its Ohio Supplement can be used to determine storm water runoff or The Rational Method, which shall be the minimum design. (Ord. 864. Passed 5-4-09.)