Erosion, storage, and transport of sediment in two subbasins of the Rio Puerco, New Mexico

Abstract

Arroyos in the American Southwest proceed through cut-and-fi ll cycles that operate at centennial to millennial time scales. The geomorphic community has put much effort into understanding the causes of arroyo cutting in the late Quaternary and in the modern rec ord (late 1800s), while little effort has gone into understanding how arroyos fi ll and the sources of this fi ll. Here, we successfully develop a geographic information system (GIS)-modeled sediment budget that is based on detailed fi eld measurements of hillslope and channel erosion and deposition. Field measurements were made in two arroyo basins draining different lithologies and undergoing different land disturbance (Volcano Hill Wash, 9.30 km 2 ; Arroyo Chavez, 2.11 km 2 ) over a 3 yr period.Both basins have incised channels that formed in response to the late nineteenth-century incision of the Rio Puerco. Large volumes of sediment were generated during arroyo incision, equal to more than 100 yr of the current annual total sediment load (bed load + suspended load) in each basin. Downstream reaches in both arroyos are presently aggrading, and the main source of the sediment is from channel erosion in upstream reaches and fi rst-and second-order tributaries. The sediment budget shows that channel erosion is the largest source of sediment in the current stage of the arroyo cycle: 98% and 80% of the sediment exported out of Volcano Hill Wash and Arroyo Chavez, respectively. The geomorphic surface most affected by arroyo incision and one of the most important sediment sources is the valley alluvium, where channel erosion, gullying, soil piping, and grazing all occur. Erosion rates calculated for the entire Volcano Hill Wash (-0.26 mm/yr) and Arroyo Chavez (-0.53 mm/yr) basins are higher than the modeled upland erosion rates in each basin, refl ecting the large contributions from channel erosion. Erosion rates in each basin are affected by a combination of land disturbance (grazing) and lithology-erodible sandstones and shales in Arroyo Chavez compared with basalt for Volcano Hill Wash. Despite these differences, hillslope sediment yields are similar to long-term denudation rates. As the arroyo fi lls over time from mouth to headwaters, hillslope sediment becomes a more signifi cant sediment source.

Processes of arroyo filling in northern New Mexico, USA

“…Waves of incision may be followed by upstream propagating waves of deposition as a result of local widening and transport of sediment from incising reaches upstream (Schumm and Hadley, 1957;Gellis et al, 2012). Experimental studies have sometimes shown that the wave of deposition is followed by re-incision as the sediment source becomes more remote ("complex response" of Schumm and Parker, 1973).…”

“…Arroyos are deep, oversized channels usually with vertical or steeply cut walls of silt, clay, or sand (Dodge, 1902;Schumm and Hadley, 1957;Cooke and Reeves, 1976;Gellis et al, 2012). They occur in semiarid or arid regions worldwide (Prosser et al, 2001;Sancho et al, 2008;Mehl and Zárate, 2012;Boardman, 2014).…”

“…4). This decrease in sediment transport can be attributed to the change from arroyo cutting to fi lling at the study site as well as a decrease in erosion upstream and lower fl ows (Gellis et al, 2012). The Rio Puerco is a major source of sediment to Elephant Butte Reservoir on the Rio Grande ( Fig.…”

“…As a result, there is a shift from arroyo cutting to fi lling: Sediment deposition begins to occur within the arroyo, vegetation becomes established on the arroyo fl oor, and channel narrowing and fl oodplain formation occur (Schumm and Hadley, 1957;Gellis et al, 2012;Fig. 1).…”

“…This rate of sediment storage within our 55 km study reach was 24% of the long-term bedrock denudation rate of the basin determined from cosmogenic isotopes (2.0 × 10 6 t/yr; Clapp et al, 2001;Bierman et al, 2005). Although the study reach of the Rio Puerco has been fi lling for more than half a century, upstream tributaries are still eroding (Gellis et al, 2012). As a result, the sum of the average annual storage on March 16, 2015 gsabulletin.gsapubs.org Downloaded from within the study reach and the average annual suspended sediment discharge at Bernardo is 3.54 × 10 6 t/yr, which is 75% greater than the long-term bedrock denudation rate of the basin.…”