Impact of drainage integration on basin geomorphology and landform evolution: A case study along the Salt and Verde rivers, Sonoran Desert, USA
Introduction
Drainage integration occurs when former hydrologically closed (endorheic) or disconnected drainage basins merge to form a new hydro-geomorphic system (Hilgendorft et al., this issue). Much of drainage integration research has focused on the evolution of main-stem river systems within a drainage basin, resulting in a burgeoning understanding of processes that drive integration (Oberlander, 1965; Meek, 1989; House et al., 2005; Douglass and Schmeeckle, 2007; House et al., 2008; Reheis and Redwine, 2008; Douglass et al., 2009; Gunnell and Harbor, 2010; Lee et al., 2011; Pearthree and House, 2014; García-Castellanos and Larrasoana, 2015; Repasch et al., 2017; Geurts et al., 2018; Geurts et al., this issue; Skotnicki et al., this issue). Despite this, comparatively few studies have investigated the variety and significance of landforms that experienced a basin-scale response to integration processes. Recent studies investigating these basins have begun to illuminate basin-wide, dynamic responses (Geurts et al., 2018; Geurts et al., this issue) of those landscapes — including pediment adjustment (Larson et al., 2010; Larson et al., 2014; Larson et al., 2016) and tributary response (Jungers and Heimsath, 2019). These studies reveal the potential for aiding in the development of conceptual models of basin and landform evolution during and post integration (Menges and Pearthree, 1989) – with significance that goes beyond geomorphology to basin evolution (Roberts et al., 1994), basin sedimentation (Richard et al., 2007), carbon dioxide sequestration (Gootee, 2013), groundwater resource management (Laney and Hahn, 1986; Reynolds and Bartlett, 2002; Skotnicki and DePonty, this issue), and natural hazard mitigation (Jeong et al., 2018).
This paper attempts to shed light on basin-scale adjustment and the landforms resulting from drainage integration. We do this by presenting a variety of landforms, observed and interpreted over >20 yr of field investigation throughout the spatial extent of formerly closed, endorheic basins along the now through-flowing lower Salt and Verde rivers, Arizona, USA (Fig. 1, Fig. 2, Fig. 3).
Section snippets
Study area: the Salt and Verde rivers of central Arizona
Decades of research in central Arizona have led to estimates for the timing and hypothesized potential mechanisms, supported by abundant evidence, of integration of the Salt, Verde, and Gila rivers through the Phoenix metropolitan area (Pope, 1974; Péwé, 1978; Skotnicki, 1996; Skotnicki and Leighty, 1997; Skotnicki and Spencer, 2001; Skotnicki et al., 2003; Block, 2007; Douglass et al., 2009; Larson et al., 2010; Jungers and Heimsath, 2016; Larson et al., 2016; Jungers and Heimsath, 2019; Dorn
Methods
Though much of the contemporary study of geomorphology is tied to quantitative measurement and modeling, the origin of the field of geomorphology in natural history has meant that observation and interpretation have always been a fundamental part of a geomorphologist's research (Rhoads and Thorn, 1996). Indeed, the complexity of geomorphic systems and unique suite of conditions within a given landscape-system fundamentally requires observation and field investigation to understand natural
Landforms as evidence of and response to drainage integration
Basin-scale adjustment to integration processes is largely driven by base-level change, which, itself, is a result of integration. Table 1 summarizes our analysis of how base level changed throughout the late Pliocene and Quaternary in response to drainage integration. In what follows, we first present a variety of landforms tied directly and specifically to basin landscape evolution driven by integration processes along specific reaches of the Salt and Verde rivers. We then highlight classic
Discussion
The location of much of the study area (Fig. 1, Fig. 3) in the Sonoran Desert means that classic desert landforms such as pediments (Kesel, 1977; Péwé, 1978; Parsons and Abrahams, 1984; Pelletier, 2010) and alluvial fans (Melton, 1965; Bull, 1984; Huckleberry, 1994; Melton, 1965; Bull, 1984; Huckleberry, 1994) evolved as a product of drainage integration processes that established through-flowing drainages throughout central Arizona. Our analysis (Table 1) indicates that extensive pediments of
Conclusion
The establishment of a through-flowing river system in a setting formerly occupied only by endorheic drainage can dramatically alter the geomorphology of an integrated basin. The Salt River and Verde River systems of central Arizona cross the Basin and Range extensional tectonic setting and likely established their present course sometime between ca. 2.2–2.8 Ma. A series of drainage integration events occurred that connected the basins through which they now flow. Landforms (e.g., stream
Declaration of competing interest
In regards to the research and findings reported in this paper:
- 1)
The authors of this manuscript have no competing financial interests or investments.
- 2)
Nor do they have personal relationships or conflicts of interest.
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