Quantifying Hydraulic Geometry and Whitewater Coverage for Steep Proglacial Streams to Support Process-Based Stream...

Area of Science:

• * Hydrology and Fluvial Geomorphology
• * Environmental Remote Sensing
• * Water Resource Management

Background:

• * At-a-station hydraulic geometry (AASHG) describes riverine dependencies on discharge, crucial for stream temperature modeling.
• * Steep proglacial streams present challenges for AASHG derivation due to complex morphology and flow dynamics.
• * Whitewater coverage influences stream surface albedo, a key factor in thermal energy exchange.

Purpose of the Study:

• * To derive AASHG relationships for a steep proglacial channel using novel methods.
• * To quantify whitewater coverage and its relationship with discharge.
• * To support process-based stream temperature modeling by integrating hydraulic and thermal data.

Main Methods:

• * Combined tracer injections with drone-based photogrammetry for data acquisition.
• * Modeled velocity-discharge and width-discharge relationships using power-law functions.
• * Quantified whitewater coverage as a fraction of stream surface area across varying discharges.

Main Results:

• * Power-law functions reasonably characterized velocity-discharge and width-discharge relationships, with sub-reach variations.
• * Whitewater coverage exceeded 50% and showed a significant positive linear relationship with discharge within the sampled flow range.
• * Stream albedo is likely higher than typically assumed in models; glacier retreat may increase downstream warming.

Conclusions:

• * AASHG relationships and whitewater coverage in steep proglacial streams can be effectively quantified using integrated remote sensing and tracer techniques.
• * Significant whitewater coverage necessitates higher albedo values in thermal models.
• * Glacier retreat-induced discharge reduction will likely lower stream albedo and increase downstream warming, compounding other flow-dependent thermal effects.