Arizona Geological Survey OPEN-FILE REPORT OFR 08-06

Arizona Geological Survey
indicate levels of relative age distinctions between debris‐flow deposits of broadly similar ages. The
generalized labeling scheme presented below was modified as needed for each canyon.
Figure 3. An example from Soldier Canyon of fresh 2006 debris‐flow deposits (yellow circle) overlying
older undisturbed deposits (blue circles).
Debris‐flow deposits often exhibit characteristic morphology based on depositional processes. Levees
are linear aggregations of boulders and cobbles that form along lateral margins of debris flows during
downslope transport (Figure 4). Snouts are wider, lobate aggregations of boulders and cobbles that form
where debris flows terminate (Figure 5). When characteristic morphology was identified during field
mapping or through aerial photographic interpretation, debris‐flow deposits were classified as either
levee (subscript L) or snout (subscript S). Deposits of uncertain morphology, due to either partial burial
or disturbance, were undifferentiated (no subscript L or S). Two other types of coarse cobble‐ and
boulder‐dominated deposits, found some distance from the mountain front, were also classified based
on morphology. Boulder‐bar (B) deposits exhibited some debris‐flow characteristics but could not be
clearly identified to due to partial burial or disturbance of deposits. Coarse, unsorted cobble and boulder
(C) deposits were exposed along channel banks bottoms, and interpreted as older debris‐flow deposits
reworked by either high discharge fluvial processes or secondary debris flows. Both B and C deposits
were found at the lower extent of mapped debris‐flow deposits. Many of the areas mapped have been
disturbed to some degree by development. In some areas older debris‐flow deposits evident in earlier
aerial photographs have been obscured by recent development.
11