Sean,
 
My "expertise" about dams is limited to check dams of south-central
Arizona so I won't hazard a comment about the photographed dam, but I
will offer a reference that may be useful to you.
 
It is follows:
 
Gaines Stanley H. (compiler)
1938    Bibliography on Soil Erosion and Soil and Water Conservation.
Miscellaneous Publication No. 312. United States Department of
Agriculture, Washington, D.C. (with abstracts by Francesca Vincent,
Marion Bloom and James F. Carter).
 
Several references cited in the bib that may be of interest to you are
listed below:
 
#1684
Anonymous
1937    Stone Tames A Stream. Capper's Farmer 48:68, illustrated.
February.
References a sausage groin in Montana.
 
#1701
Gillette, H.P.
1918    Novel and Economic Method of Controlling Streams. Engineering
and Contracting 50:339-340, illus. October.
 
#1734
Muehleisen, G.
1926    The Porous Dam Method of Erosion Control. Agricultural
Engineering 7:350-351, illus. October.
 
#1738
Olmsted, F.H.
1916 Control of Mountain Torrents by Check Dams. Engineering News
75:314-315., illus. February 17.
 
The articles may not describe the dam you are researching, but they may
offer clues about why it was constructed the way it is, or convey what
the builders were trying to do with it. Also I hope I got the
magazine/journal articles correct; they are abbreviated only by Gaines
(1938).
 
In addition, several sources not listed above reference "rolled earth"
and "rolled-fill" dam construction, but I haven't a clue what these
terms mean based upon the brief abstracts following the titles.
 
my best,
 
mike gregory
Great Lakes Archaeological Research Center
Milwaukee, Wisconsin