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<br />Studies of geomorphology.--Intuitive reasoning suggests that flood deposits <br />in and adjacent to foothill streams should be related in some manner to the type <br />of flood that transported and deposited the material. This leads to the <br />hypothesis that historical flash-flood occurrences in the foothills region can be <br />identified by detailed analysis of streambed and flood-plain deposits. <br /> <br />Samples of streambed and flood-plain deposits at selected cross sections are <br />being collected and analyzed to investigate the hypothesized relationship with the <br />type of flood. Speciai emphasis is being placed on identification of deposits on <br />alluvial fans where steep tributaries flow onto flatter mainstream valley floors. <br />Slope-wash and glacial-melt deposits along valley edges are being mapped to <br />separate them from tributary alluvial deposits. <br /> <br />Studies of botany.--Other possible sources of information relating to flash- <br />flood severity and areal extent are studies of vegetation modification, including <br />tree-ring analysis and lichen-growth patterns. Flash floods are invariably <br />characterized by swift velocities, transport of large boulders and debris, and <br />overbank discharges. Significant vegetation modification occurs along streams, <br />and the vegetation that survives usually bears evidence of the flood for many <br />years. Experts in the field of botanic research are frequently able to identify <br />various kinds of vegetation modification and, in some cases, establish a time <br />reference for the occurrence of past floods. <br /> <br />Studies will be conducted to evaluate the feasibility of using tree-ring <br />analysis and lichen-growth rates to provide historical flood information. <br />Specialists from local universities and other agencies will conduct <br />reconnaissance-type tree-ring studies and investigate the feasibility of relating <br />1 ichen-growth patterns to the occurrence of floods. Future botanic research wi 11 <br />be dependent on the outcome of the feasibility studies. <br /> <br />Testing and Verifying Hydrologic Models <br /> <br />This phase will be conducted during the latter part of <br />hydrologic models will be tested, using knowledge gained <br />studies. If required, components of existing models will <br />represent physical characteristics of foothill basins. <br /> <br />the project. Various <br />during the earlier <br />be modified to better <br /> <br />An important item in hydrologic model ing is an accurate determination of the <br />areal extent of rainfall over a basin. On-site investigations will be conducted <br />following significant floods to define the areal extent of the flood-producing <br />storms. Satell ite photography and radar data will also be studied to determine <br />its possible use in defining areal extent of storms. It is anticipated that <br />knowledge gained from the total research effort can result in a more physically <br />significant hydrologic model for foothill basins than presently exists. <br /> <br />Related Research Studies <br /> <br />Although outside the scope of this project and outside the mission of the <br />U.S. Geological Survey, one important meteorological study could add valuable in- <br />formation toward solution of the foothills-flood problem. This study is mentioned <br />to encourage research effort by qualified agencies or individuals. <br /> <br />20 <br />