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Quantification and differentiation of delta and fluvial fan channel network morphometrics
Gezovich, Luke J.
Gezovich, Luke J.
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2022
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Abstract
Deltas and fluvial fans are two fan shaped landforms with complex channel networks.
Accurately differentiating between these two landforms is crucial to identifying and
understanding these two landforms on Earth, as well as on other planetary bodies like Mars and
Titan. Differentiating between these landforms is critical for infrastructure planning and sea level
rise resilience as deltas and fluvial fans will react differently to sea level rise. One significant
difference between deltas and fluvial fans is that deltas only form along shorelines where a river
enters an ocean or lake. Fluvial fans may form hundreds of kilometers inland from a shoreline
and are predominantly controlled by upstream controls. Fluvial fans form by channel avulsions
whereas deltas primarily build by mouth bar deposition and consequent channel bifurcations.
Here I present an ensemble of quantitative metrics to differentiate morphologically fluvial fans
from deltas. To achieve this, I quantify channel bifurcation/divergence angles, channel lengths
and widths between these bifurcation/divergence nodes, channel orders, and the number of
terminal channels. Previous research on delta channel morphometrics strongly suggest that
delta s exhibit an average channel bifurcation angle around 72 while maintaining a distinct
downstream non linear decrease in channel lengths and widths for successive bifurcations. Our
results show that fluvial fans differ from deltas by exhibiting a considerably smaller divergence
angle, and down fan channel length shortening that is not associated with divergence orders.
Our results further suggest there exists a statistically significant difference between deltas and
fluvial fans channel networks. These results indicate that channel network assessments show a
difference between deltas and fluvial fans, and that the channel networks need to be carefully
assessed if used for paleo shoreline estimations on planetary bodies. Additional evidence is
needed for the presence of shorelines as fluvial fans may occur at shorelines.
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