Outburst floods provide erodability estimates consistent with long-term landscape evolution.

Area of Science:

• Earth Science
• Geomorphology
• Hydrology

Background:

• Current landscape evolution models rely on semi-empirical laws linking riverbed incision to rock erodability and stream power.
• Estimating erodability in these models is challenging due to uncertainties in past climate and streamflow conditions.

Purpose of the Study:

• To develop a novel methodology for estimating outlet erodability using data from lake outburst floods.
• To improve the accuracy and applicability of landscape evolution models by reducing assumptions about past hydrology.

Main Methods:

• Utilized erosion data from 82 outburst floods triggered by overtopping lakes.
• Leveraged geomorphological evidence along spillways to constrain water discharge, bypassing assumptions about past streamflow.

Main Results:

• Obtained erodability values that quantitatively correlate with lithology, consistent with previous river erosion studies.
• Expanded the range of hydrological and temporal scales applicable to fluvial incision models.
• Demonstrated consistency between mathematical formulations of long-term and catastrophic erosional mechanisms.

Conclusions:

• The novel methodology provides reliable erodability estimates, enhancing fluvial incision models.
• Clarified the conditions conducive to runaway erosion during lake outburst floods.
• Suggests a unified understanding of landscape evolution across different timescales and erosional processes.