Question

An undeveloped 1,000-acre catchment currently is covered by pasture in good condition and it composed of hydrologic soil group C. This gives a pre-development composite CN equal to 74. A proposed urban development (post development) will change land use to:

• 55% 1/3 acre lots (30% impervious), CN = 81;
• 20% in open space in good condition, CN = 74; and
• 25% in roads, sewers and parking lots, CN = 98.

What is the increase or decrease of acre-ft. of water volume due to proposed urban development?

Answer 1

Answer:

given that

An undeveloped 1,000-acre catchment currently is covered by pasture in good condition

CN= 74 pre development

weight CN (post development)

=

S value pre development  

S value post development

home rainfall is not given - so we can not find root volume

volume increase

Q= 136 acre ft.