A wide range of climatic mechanisms have been suggested, ranging from fluctuations in groundwater levels to episodes of catastrophic flooding; and (3) Arroyo cutting and filling is an inherent behavior of semiarid drainage systems, wherein pulses of incision followed by widening and eventually aggradation migrate upstream in response to local slope anomalies.

Prior to this historic episode of arroyo-cutting, settlers characterized valley bottoms as marshy wetlands or grasslands with shallow channels.

During arroyo-cutting, observers described the upstream migration of steep headcuts during successive floods.

Some studies have identified upwards of 10 alluvial fills that predate the "Naha' alluvium, though existing age control is limited.

Hypothesis Testing If arroyo cutting events are climate-driven, what specific mechanism(s) are at play? Such evidence acts as a proxy for flood stage, which, combined with detailed surveying, can be used to calculate the paleodischarge.

Was prehistoric arroyo cutting related to this major cultural transition?

It certainly seems plausible, as archeological evidence suggests that these burgeoning cultures relied on floodwater farming.

Now, geologists are using optically-stimulated luminescence (OSL) dating where no cultural features or organic material can be found.

All of the above tools can be used to constrain the timing of past arroyo cycles in order to establish their relation to hydrological and environmental changes.

Hypothesized causes of arroyo cutting For almost a century, geologists have debated the cause of historic arroyo cutting.

Most hypotheses fit into one of three categories: (1) Intensive grazing and floodplain alteration associated with Anglo settlement led to increased runoff during storms, causing more erosive floods; (2) Arroyo cutting was the result of climate change.

In reality, each of the above hypotheses likely played some role in arroyo cutting.