Modeling Sediment Yield in Land Surface and Earth System Models: Model Comparison, Development, and Evaluation

Abstract

Sediment yield (SY) plays an important role in the global carbon cycle for carrying particulate carbon into rivers and oceans, but it is rarely represented in Earth system models (ESMs). Existing SY models have mostly been tested over a few small catchments in specific regions or in large river basins globally. By comparing the performance of eight well‐known SY models in 454 small catchments with various land covers and uses across the United States, Canada, Puerto Rico, U.S. Virgin Islands, and Guam, we identified the simple Morgan model for its better performance in representing the spatial variability of continental scale SY at spatial scales relevant to ESMs (several to hundreds of square kilometers) than other models because of a more realistic representation of runoff‐driven erosion and sediment transport capacity in the context of current data availability. The results also indicated that runoff‐driven erosion should be formulated using a power function of runoff, shear stress, or stream power to better represent the total effect of concentrated flow if gully erosion and channel erosion are not explicitly modeled. We also demonstrated that the Morgan model can be further improved by removing snowmelt‐driven runoff in modeling runoff‐driven erosion and to a minor degree by integrating a landslide model. The improved Morgan model explains 57% of the spatial variability of the measured SY. The new model also demonstrated the capability to simulate SY in cross‐validation catchments at fine temporal scales, which is important for coupling SY with other biogeochemistry processes in ESMs.

A substantial role of soil erosion in the land carbon sink and its future changes

“…The rectangles grouped in the pink box represent hydrologic fluxes (blue), vegetation conditions (green), and soil biogeochemistry (yellow) that are simulated by the ELM. On the upper right of the pink box, the symbols represent the calculation of rainfall‐driven erosion, runoff‐driven erosion, sediment transport capacity, and sediment yield (the smaller value of total erosion and transport capacity) by the improved Morgan model (Tan et al, ). On the lower right of the pink box, the symbols represent the calculation of erosional biogeochemical fluxes in ELM using the simulated sediment flux [Colour figure can be viewed at wileyonlinelibrary.com]…”

Improving Evapotranspiration Model Performance by Treating Energy Imbalance and Interaction

“…Alternatively, these hypotheses can be evaluated using a multiple-hypothesis approach within a modular framework (Clark et al, 2011). Similar methods have been used for multiple-algorithm comparisons (Tan et al, 2018). Höge et al (2018) identified four model selection classes and further classified nonconsistent or consistent model selection under a Bayesian framework or not.…”

Development of a global sediment dynamics model

“…They considered sediment detachment in hillslopes and used the Rouse number to determine whether the sediment is routed to the downstream pixel. There have also been several studies aimed to incorporate sediment processes into Earth System Model frameworks at shorter time periods (e.g., Naipal et al 2016;Tan et al 2018), but none that explicitly estimates the movement of both suspended sediment and bedload. Cohen et al (2013) developed WBMsed, which is one of the few distributed global-scale sediment models to estimate suspended sediment flow at a daily timescale.…”