Climate Change and the Episodicity of Sediment Flux of Small California Rivers

We studied the streamflow and sediment flux characteristics of the 20 largest streams entering the Pacific Ocean along the central and southern California coast, extending for 750 km from Monterey Bay to just south of the U.S./Mexico border. Drainage basins ranged in area from 120 to 10,800 km2, with headwater elevations ranging from 460 to 3770 m. Annual streamflow ranged from 0 to a maximum of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $1\times 10^{9}$ \end{document} m3/yr for the Santa Clara River in 1969, with an associated suspended sediment flux of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $46\times 10^{6}$ \end{document} ton. Trend analyses confirm that El Niño/Southern Oscillation–induced climate changes recur on a multidecadal time scale in general agreement with the Pacific/North American climate pattern: a dry climate extending from 1944 to about 1968 and a wet climate extending from about 1969 to the present. The dry period is characterized by consistently low annual river sediment flux. The wet period has a mean annual suspended sediment flux about five times greater, caused by strong El Niño events that produce floods with an average recurrence of ca. 5 yr. The sediment flux of the rivers during the three major flood years averages 27 times greater than the annual flux during the previous dry climate. The effects of climate change are superimposed on erodibility associated with basin geology. The sediment yield of the faulted, overturned Cenozoic sediments of the Transverse Ranges