Record Details
page 4
Digital Collections at BYU
| Field | Value |
|---|---|
| Title | page 4 Diamond Fork System Final Supplement to the Final Environmental Impact Statement, page 4 |
| Coverage | Electronic reproduction; |
| Format | 4 text/PDF |
| Rights | Brigham Young University; http://lib.byu.edu/about/copyright/generic.php Public Domain Public |
| Language | English; eng; en |
| Relation | Central Utah Project; Western Waters Digital Library; comment letter no 10 page 4 of 12 cottonwoods cotton woods are only viable for a couple of weeks following 11 1 1 dispersal scott et al 1993 just as important to riparian vegetation maintenance is the ummer summer s haseoo base hase ro flow w lev ley hev level levei el the importance of flow duration can not be overstated in general it is the duration of ofhydrologic hydrologic support and not the absolute magnitude that defines wetland communities including riparian habitats mitsch and gosselink 1993 while upland vegetation can tolerate drought riparian vegetation requires access to a water table throughout the entire growing season stromberg et al 1994 consequently changes in either water table recharge flows such as spring floods or the growing season water table can result in mortality of established species and the two can not be uncoupled patton and mckee 1995 that is simply providing a spring peak but depleting the summer water table can not maintain riparian vegetation in fact the idea that existing stable streams with existing cottonwood forest could be maintained through truncation of the annual hydrograph and simple provision of a recession curve was questioned at the 1997 society of wetland scientists riparian symposium by noted riparian scientists 2 topographic position and local site conditions eg soils floodplain flood plain morpho morphology morpholoo loo 100 Y provide an additional set of factors affecting both current riparian vegetation distribution and future establishment processes EM 1995 scott et al 1994 similar factors affect how riparian vegetation responds to flow changes 3 A very important factor in riparian and channel responses to flow changes is how the proposed action will affect sediment transport the effective discharge or the range of f flows lows over which most sediment transport occurs is strongly affected by flow duration and not as much by the absolute magnitude of flows andrews 1980 4 riparian species respond differently to flow changes andblanket and blanket generalizations about riparian impacts can not be made without identifying the dominant species and their likely responses to a range of ofhydrologic hydrologic parameters auble et al 1995 patton and mckee 1995 davis 1997 diamond fork riparian ecology issues based on an understanding of the actual riparian conditions in in diamond fork and riparian requirements associated with all aspects of the hydrograph I 1 suggest that the EIS did not adequately consi consider der the following ZD Z D issues issues effects of sediment transport on floodplain flood plain morph mordh morphalagy aLagy and nd resultanll xgsultant s sp ecles ecie cies eche e 3 eg establishment potenti pptentijal potentialthe aLThe the EIS identifies that a flow regime based on a simple recession curve with a continued duration of above normal summer flows will result in fine sediment deposition and rebuilding of the floodplam floodplain flood plain plam piam upon which cottonwood would subsequently establish data collected by the USFS as listed in gecy and gecy 1998 shows an effective discharge of approximately 200 cfs cs with large particle sediment transport occurring as low as 160 cfs cs based on this data it is unlikely that prolonged duration of flows above 160 cfs efs es would result in sediment deposition and floodplain flood plain building this is important as 6.7 67 67 of the total 7.5 75 75 miles of diamond fork lack a floodplain flood plain outside of the active channel to reestablish a cottonwood forest in the braided reach floodplain flood plain surfaces would have to be created at a level approximately 2.2 22 22 feet above the new bankfull ban krull kroll level requiring 4 |
| Identifier | http://cdm15999.contentdm.oclc.org/cdm/ref/collection/WesternWatersProject/id/9784 |
