Grainsize Dependent Transport and Deposition in a Landscape Evolution Model

Emry, E.; Han, Kyungdoe; Berry, Michael A.; Wijk, Jolante van; Wilson, John L.; Leary, Ryan J.; García-Castellanos, Daniel

doi:10.1130/abs/2019am-338819

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“…We modified TISC to add the periodic boundary condition and to directly model the simple uplift scenario described above; we did not use the isostasy model. TISC considers only a uniform grain size; without modification (e.g., Emry et al, 2019), it cannot capture properties of alluvial deposits that are sensitive to grain‐size distribution. TISC simulates deltaic sedimentation (i.e., subaqueous deposition) by sequentially distributing sediment from the inlet cells while reducing transport over distance using the sediment‐transport length scale (

l_{f}

).…”

Section: Alluvial Fan Modelling Using a Landscape Evolution Codementioning

confidence: 99%

Autonomous generation of alluvial fans in landscape evolution models

Han

Wilson

Emry

2023

Earth Surf Processes Landf

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We develop a robust and simple rule‐based algorithm to autonomously simulate alluvial fan deposition and evolution under continuously developing landscape conditions without prescribing deposition locations or imposing topographic constraints. Augmented with this algorithm, landscape evolution models are capable of dynamically detecting locations of potential fan deposition by statistical measures of surface topography and fluvial dynamics, then depositing fan sediments where and when the developed conditions require. To assess the method's efficacy in depositing sediment at a mountain‐valley transition zone characterized by a transport surface that permits unobstructed exit of sediment and water, a hypothetical scenario is created that involves a frontal, normal fault. It is followed by a series of sensitivity analyses to ascertain the influence of parameters affecting fan deposition and secondary processes. Uplift (u) and precipitation significantly impact fan morphological characteristics, which are within the range of real‐world fans. Higher rates of each cause the notable expansion of the fan area except in cases of exceptionally high precipitation rates. Fan area has a power‐law relationship with most of the tested parameters, , where is erodibility (lithology), and are fluvial parameters, and is catchment area (~0.9). This study is the first showcasing fan power‐law relationships using numerical modelling. While fan area increases with precipitation, there exists a threshold beyond which fan area diminishes, and the formation of fans ceases altogether. The algorithm provides a basis for improving mechanistic understanding of fans by offering a robust platform for testing process dominance and scaling. The results demonstrate its applicability for landscape evolution simulation over a long time and broad spatial scales. We also investigate the hydrological significance of including autonomously generated alluvial fans in coupled landscape evolution—hydrology models that focus on groundwater as well as surface water hydrology.

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