Appendix C 

 Happy Valley Hydrology 



activities would reduce the erosion and sediment delivery rates from the current levels, and 

 would improve water quality in the proposed project area. 



Cumulative Effects 



No Action Alternative 



Cumulative effects of the no action alternative on water quality and water yield would be similar 

 to the situations described in the existing conditions. The water quality and water yield would be 

 unaffected by the no action alternative, and the stream and ephemeral draws in the proposed 

 project area would continue to be affected by natural and pre-existing conditions. 



Action Alternative 



Risk of sediment delivery in the proposed project area would be reduced from current levels. 

 Decommissioning of existing poorly located roads would reduce erosion rates and lower the risk 

 of sediment delivery to other areas. 



Past activity in and around the proposed project area has mainly consisted of residential home 

 constniction and agricultural use, with some areas being managed for timber production. On 

 sites where timber was har\'ested, there has been substantial vegetative and hydrologic recovery 

 with no apparent impact on water yield increases. 



The proposal is to selectively harvest the stand by commercial thinning, shelterwood, and seed 

 tree prescriptions. Watershed cumulative effects are not anticipated for the following reasons: 

 1) The selective nature of the harvest over most of the proposed project area would leave 

 substantial amounts of live trees on the site, and is designed to allow more rapid growth of the 

 remaining trees, 2) The well-drained nature of the soils would produce little or no detectable 

 change in water yield, 4) The stream and ephemeral draws within the project area are stable and 

 vegetated with a dense mat of grass and forb vegetation, making them capable of handling 

 potential water yield increases without destabilizing, and 5) All of the proposed harvesting would 

 occur in an intermittent drainage with no surface delivery to another body of water, therefore 

 potential increases in sediment or water yield from harvest activities would not affect 

 downstream waters. 



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