@article{Kim2014,
title = {Process dominance shift in solute chemistry as revealed by long-term high-frequency water chemistry observations of groundwater flowing through weathered argillite underlying a steep forested hillslope},
author = {Hyojin Kim and James K.B. Bishop and William E. Dietrich and Inez Y. Funga
},
url = {https://angelo.berkeley.edu/wp-content/uploads/Kim_2014_GeochCosmoActa.pdf},
doi = {10.1016/j.gca.2014.05.011},
year = {2014},
date = {2014-09-01},
journal = {Geochimica et Cosmochimica Acta},
volume = {140},
pages = {1-19},
abstract = {Significant solute flux from the weathered bedrock zone – which underlies soils and saprolite – has been suggested by many studies. However, controlling processes for the hydrochemistry dynamics in this zone are poorly understood. This work reports the first results from a four-year (2009–2012) high-frequency (1–3 day) monitoring of major solutes (Ca, Mg, Na, K and Si) in the perched, dynamic groundwater in a 4000 m2 zero-order basin located at the Angelo Coast Range Reserve, Northern California. Groundwater samples were autonomously collected at three wells (downslope, mid-slope, and upslope) aligned with the axis of the drainage. Rain and throughfall samples, profiles of well headspace pCO2, vertical profiles and time series of groundwater temperature, and contemporaneous data from an extensive hydrologic and climate sensor network provided the framework for data analysis.

All runoff at this soil-mantled site occurs by vertical unsaturated flow through a 5–25 m thick weathered argillite and then by lateral flows to the adjacent channel as groundwater perched over fresher bedrock. Driven by strongly seasonal rainfall, over each of the four years of observations, the hydrochemistry of the groundwater at each well repeats an annual cycle, which can be explained by two end-member processes. The first end-member process, which dominates during the winter high-flow season in mid- and upslope areas, is CO2 enhanced cation exchange reaction in the vadose zone in the more shallow conductive weathered bedrock. This process rapidly increases the cation concentrations of the infiltrated rainwater, which is responsible for the lowest cation concentration of groundwater. The second-end member process occurs in the deeper perched groundwater and either dominates year-round (at the downslope well) or becomes progressively dominant during low flow season at the two upper slope wells. This process is the equilibrium reaction with minerals such as calcite and clay minerals, but not with primary minerals, suggesting the critical role of the residence time of the water. Collectively, our measurements reveal that the hydrochemistry dynamics of the groundwater in the weathered bedrock zone is governed by two end-member processes whose dominance varies with critical zone structure, the relative importance of vadose versus groundwater zone processes, and thus with the seasonal variation of the chemistry of recharge and runoff.},
keywords = {bedrock, hydrochemistry, solute flux},
pubstate = {published},
tppubtype = {article}
}

@article{Rempe2014,
title = {A bottom-up control on fresh-bedrock topography under landscapes},
author = {Daniella M. Rempe and William E. Dietrich},
url = {https://angelo.berkeley.edu/wp-content/uploads/Rempe_2014_PNAS.pdf},
doi = {10.1073/pnas.1404763111},
year = {2014},
date = {2014-05-06},
journal = {PNAS},
volume = {111},
number = {18},
pages = {6576–6581},
abstract = {The depth to unweathered bedrock beneath landscapes influences subsurface runoff paths, erosional processes, moisture availability to biota, and water flux to the atmosphere. Here we propose a quantitative model to predict the vertical extent of weathered rock underlying soil-mantled hillslopes. We hypothesize that once fresh bedrock, saturated with nearly stagnant fluid, is advected into the near surface through uplift and erosion, channel incision produces a lateral head gradient within the fresh bedrock inducing drainage toward the channel. Drainage of the fresh bedrock causes weathering through drying and permits the introduction of atmospheric and biotically controlled acids and oxidants such that the boundary between weathered and unweathered bedrock is set by the uppermost elevation of undrained fresh bedrock, Zb. The slow drainage of fresh bedrock exerts a “bottom up” control on the advance of the weathering front. The thickness of the weathered zone is calculated as the difference between the predicted topographic surface profile (driven by erosion) and the predicted groundwater profile (driven by drainage of fresh bedrock). For the steady-state, soil-mantled case, a coupled analytical solution arises in which both profiles are driven by channel incision. The model predicts a thickening of the weathered zone upslope and, consequently, a progressive upslope increase in the residence time of bedrock in the weathered zone. Two nondimensional numbers corresponding to the mean hillslope gradient and mean groundwater-table gradient emerge and their ratio defines the proportion of the hillslope relief that is unweathered. Field data from three field sites are consistent with model predictions.},
keywords = {bedrock, topography},
pubstate = {published},
tppubtype = {article}
}

@article{Sklar2004b,
title = {A mechanistic model for river incision into bedrock by saltating bedload},
author = {Leonard S. Sklar and William E. Dietrich},
url = {https://angelo.berkeley.edu/wp-content/uploads/Sklar_2004_WaterResRes.pdf},
doi = {10.1029/2003WR002496},
year = {2004},
date = {2004-06-18},
journal = {Water Resources Research},
volume = {40},
number = {6},
abstract = {Abrasion by bed load is a ubiquitous and sometimes dominant erosional mechanism for fluvial incision into bedrock. Here we develop a model for bedrock abrasion by saltating bed load wherein the wear rate depends linearly on the flux of impact kinetic energy normal to the bed and on the fraction of the bed that is not armored by transient deposits of alluvium. We assume that the extent of alluvial bed cover depends on the ratio of coarse sediment supply to bed load transport capacity. Particle impact velocity and impact frequency depend on saltation trajectories, which can be predicted using empirical functions of excess shear stress. The model predicts a nonlinear dependence of bedrock abrasion rate on both sediment supply and transport capacity. Maximum wear rates occur at moderate relative supply rates due to the tradeoff between the availability of abrasive tools and the partial alluviation of the bedrock bed. Maximum wear rates also occur at intermediate levels of excess shear stress due to the reduction in impact frequency as grain motion approaches the threshold of suspension. Measurements of bedrock wear in a laboratory abrasion mill agree well with model predictions and allow calibration of the one free model parameter, which relates rock strength to rock resistance to abrasive wear. The model results suggest that grain size and sediment supply are fundamental controls on bedrock incision rates, not only by bed load abrasion but also by all other mechanisms that require bedrock to be exposed in the channel bed.},
keywords = {bedrock, river incision, saltating bedload},
pubstate = {published},
tppubtype = {article}
}

@article{Siedl1992,
title = {The problem of channel erosion into bedrock},
author = {M.A. Siedl and W.E. Dietrich},
url = {https://angelo.berkeley.edu/wp-content/uploads/Seidl_1992_CatenaSuppl.pdf},
year = {1992},
date = {1992-00-00},
journal = {Catena Suppl.},
volume = {23},
pages = {101-124},
abstract = {Although river incision into the bedrock of uplifted regions creates the dissected topography of landscapes, little is known about the process of channel erosion into
bedrock. Here we present a testable framework for the study of fluvial incision into
bedrock that combines theory with field observation. We quantify a simple erosion
law by measuring drainage areas and slopes on both principal channels and tributaries. The data suggest that both a bedrock tributary and main stem will lower at the same rate at their confluence if the ratio of main stem to tributary drainage
area equals the ratio of tributary to main stem channel slope at the junction. Erosion
across several tributary junctions is therefore linearly related to stream power.
Tributary slopes greater than about 0.2 deviate from this linear prediction,
apparentiy because debris flows scour these steep tributaries. Further field study
suggests that the common elevation of tributary and main stem may result from the
upslope propagation of locally steep reaches generated at tributary mouths. This
propagation continues only to the point on the channel where the channel slope is
too steep to preserve the oversteepened reach, or knickpoint, and debris flow scour
dominates channel erosion.
Our results suggest three general mechanisms by which bedrock channels erode:
(1) vertical wearing of the channel bed due to stream flow, by such processes as
abrasion by transported particles and dissolution; (2) scour by periodic debris flows;
and (3) knickpoint propagation. Consequently, application of a single erosion law to the entire bedrock channel network may be inappropriate. },
keywords = {bedrock, channel erosion, erosion law},
pubstate = {published},
tppubtype = {article}
}