N.H. Code Admin. R. Env-Wr 403.05

Current through Register No. 25, June 20, 2024

Section Env-Wr 403.05 - Hydrologic Investigations

(a) Hydrologic investigations shall be performed on the entire contributing drainage area.

(b) Precipitation estimates for the design flood shall be obtained from:

(1) NRCC Research Publication RR 93-5, Atlas of Precipitation Extremes for Northeastern United States and Southeastern Canada, 1993, available as noted in Appendix B; or

(2) U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Hydrometeorological Report No. 51, Probable Maximum Precipitation Estimates, United States East of the 105^th Meridian, June 1978, available as noted in Appendix B.

(c) Hydrologic modeling for 50-year or 100-year storms shall incorporate the following:

(1) The size of the drainage area;

(2) The shape of the drainage area;

(3) Antecedent moisture condition 2, as defined in the USDA NRCS National Engineering Handbook, 210-VI-NEH-630.10, July 2004, available as noted in Appendix B;

(4) Ground slopes;

(5) Soil types;

(6) Vegetation;

(7) Land use;

(8) Distribution of varying precipitation amounts throughout the watershed; and

(9) Ponds, swamps, and other factors affecting the amount and rate of runoff.

(d) The storm duration used in the modeling shall exceed the time for water to flow from the outermost point in the system to the subject location so as to ensure that the total runoff volume will be included in the routing of the storm through the dam structure.

N.H. Code Admin. R. Env-Wr 403.05

#1716, eff 2-20-81; ss by #2207, eff 12-13-82; ss by #2900, eff 11-7-84, EXPIRED 11-7-90

New. #5080, eff 2-22-91; rpld by #6462-B, eff 2-21-97

New. #8414, eff 8-20-05; ss by #10510, eff 1-22-14