https://experience.arcgis.com/experience/9aa09c1728634be0bb3ac64a0de82578

This interactive application presents a terrain-based avalanche susceptibility model for the central Sierra Nevada corridor spanning the Tahoe National Forest and Eldorado National Forest. The model identifies and classifies terrain where avalanche release is more likely based on topographic characteristics derived from a digital elevation model.

Model Overview

The avalanche susceptibility surface was generated using a multi-factor terrain analysis incorporating:

• Slope (primary driver) – Slopes between 25° and 60° were evaluated, with peak weighting assigned to 35–40° terrain where slab avalanches most commonly initiate.

• Aspect – North through northeast-facing slopes were weighted higher due to reduced solar radiation and greater potential for persistent weak layers.

• Curvature – Convex terrain features were emphasized, as rollovers and convexities often promote slab tension and fracture initiation.

• Elevation constraint – Analysis was limited to elevations ≥ 2,000 meters to represent sustained snowpack zones.

These variables were combined using a weighted overlay approach to generate a five-class susceptibility surface:

1. Very Low

2. Low

3. Moderate

4. High

5. Very High

The resulting surface represents terrain susceptibility, not real-time avalanche conditions.

Trail Integration

The viewer includes an interactive trail network layer. Users may:

• Search for trails by name

• Zoom directly to selected trails

• View terrain susceptibility patterns intersecting trail corridors

This enables users to visually assess where recreation routes intersect higher-susceptibility terrain.

Community Observations

A Survey123 form is integrated into this application to allow users to submit field observations including:

• Avalanche occurrence

• Signs of instability

• Observed debris

• Photos and descriptive comments

Submitted observations are displayed in the map and provide community-based situational awareness. All submissions are user-generated and unverified.

Important Disclaimer

This application represents a modeled terrain susceptibility assessment based solely on static topographic factors. It does not incorporate:

• Current weather conditions

• Snowpack structure

• Wind loading events

• Recent storm cycles

• Official avalanche forecasts

This viewer is not a substitute for avalanche bulletins issued by professional forecasting agencies. Users must consult official avalanche forecasts and practice appropriate backcountry safety protocols.