1. Catchment‐Averaged Erosion Rates Reveal Signals of Divide Migration and Drainage Capture.
- Author
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Hoskins, A. M., Attal, M., Mudd, S. M., and Castillo, M.
- Subjects
WATER management ,NATURAL resources ,WATERSHEDS ,RAINFALL ,LANDSCAPE changes - Abstract
Divide migration and drainage capture contribute to drainage reorganization. The relative contributions of each are debated, as are the extent to which an observable signal of drainage reorganization may be preserved in quantifiable erosion rates. We numerically model divide migration and drainage capture, and monitor the effects on catchment‐averaged erosion rates in the growing (area gaining) and shrinking (area losing) catchments. Divide migration produces a rapid increase in catchment‐averaged erosion rates in the headwaters of the growing catchment. However, we find this catchment‐averaged erosion rate signal is quickly obscured with increasing distance downstream in non‐uniform uplift settings, limiting our ability to detect divide migration through catchment‐averaged erosion rate measurements in non‐uniform uplift settings. Drainage capture produces the strongest catchment‐averaged erosion rate signal immediately adjacent to the point of capture. We find this signal persists in the landscape longest, and without depleting in magnitude, in the area upstream of the point of capture. The Sierra la Laguna mountain range (Mexico) displays substantial evidence of recent and ongoing drainage capture across the main drainage divide, including: beheaded catchments, windgaps, barbed drainages, χ $\chi $ profiles and across divide Gilbert Metrics. We use the Sierra la Laguna to test the detectability of drainage reorganization related catchment‐averaged erosion rate signals in a natural setting. Be10 ${}^{10}Be$‐derived catchment‐averaged erosion rates are found to be twice as fast in the suspected growing catchment headwaters (0.17 mmyr−1 $mm\ y{r}^{-1}$) relative to the shrinking catchment headwaters (0.09 mmyr−1 $mm\ y{r}^{-1}$). Catchment‐averaged erosion rates, with distance downstream, share similarities with our drainage capture modeling. Plain Language Summary: An area of land drained by a single river is a drainage basin. The boundary between two neighboring basins is the drainage divide. Over long enough periods these drainage divides move. This results in one basin gaining area and one basin losing area. The basin that gains area captures more rain, meaning the river grows, becoming more powerful. On the other hand, the basin that loses area captures less rain, meaning the river shrinks, becoming less powerful. We simulate this area transfer using mathematical equations that describe how landscapes change with time. We show that when a river gains area, it is easier for that river to remove material from the landscape, increasing erosion rates. Conversely, when a river loses area, it becomes more difficult for that river to remove material from the landscape, decreasing erosion rates. By sampling sand in rivers where we suspect this drainage area transfer has occurred, in two neighboring basins of the Sierra la Laguna mountain range in Mexico, we detect this difference in erosion rates between the basin that has gained area and increased erosion, and the basin that has lost area and decreased erosion. This work has implications for water resource management and natural hazard planning. Key Points: Divide migration and drainage capture erosion rate signals are strongest in headwaters adjacent to the area of transferDrainage capture erosion rate signals are preserved longest, and without depletion in magnitude, upstream of the point of capture10Be‐derived Erosion rates in the Sierra la Laguna are consistent with our modeled signals of drainage capture [ABSTRACT FROM AUTHOR]
- Published
- 2024
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