DSAS Introduction and Expected Results

Main Ideas / Lessons

• The video is a walkthrough of how to use the Digital Shoreline Analysis System (DSAS) Version 6 (standalone), created by the USGS.
• DSAS v6 is similar to v5.1, but differs because it is now standalone and not integrated with ArcMap. The tool is moving toward ArcGIS Pro, and DSAS v6 works separately from ArcMap.
• The workflow generally follows this sequence:
  1. Prepare/convert required input layers (typically in ArcGIS Pro).
  2. Import GeoJSON layers into DSAS v6.
  3. DSAS generates transects (via the cast/transaction-style tool).
  4. DSAS calculates rate of shoreline change (via the calculate-rates tool).
• Outputs include:
  • Change classification along transects (erosion / neutral / deposition)
  • A summary statistics report

Step-by-Step Methodology (Workflow and Instructions)

1) Set Up DSAS v6 / Interface Basics

• Download and install DSAS v6 (standalone).
• Use DSAS documentation on the USGS website:
  • No updated v6 user guide is available yet (per the presenter), so the walkthrough relies mainly on v5.1 documentation while noting differences.
• Review the DSAS tour, especially the “what’s new”/settings sections.
• In DSAS settings:
  • Link your data folders using the data library.
  • DSAS displays only specific file types—emphasized in the video as GeoJSON.

2) Prepare Input Data Conceptually (Mostly Outside DSAS)

DSAS requires:

• A Baseline (offshore reference line)
• Multiple Shorelines (dated shoreline positions)

Notes from the presenter:

• Baseline/shoreline requirements are described in the USGS user handbook, and for v6 they are the same as in v5.1.
• Baseline and shoreline digitizing/conversion is done in ArcGIS Pro:
  • Digitize baseline and shorelines on imagery.
  • Convert outputs to GeoJSON before importing into DSAS.

3) Import Baseline and Shoreline GeoJSON Files into DSAS

• Locate the DSAS sample data folder (the presenter uses samples downloaded locally).
• In DSAS:
  • Add/select the Baseline layer.
  • Add/select the Shoreline layer(s).
• Resolve attribute requirements flagged by DSAS:
  • Date field must be named/typed as date.
  • Uncertainty field must be named/typed as uncertainty
    • Default uncertainty mentioned: 10
  • Baseline ID uses ID for the offshore baseline.
• Confirm baseline location and orientation visually:
  • Baseline should be a set distance offshore.
  • It should be parallel to the shoreline so transects generate correctly and don’t intersect shoreline features improperly.

4) Generate Transects (Cast Transects Tool)

• Use the cast transects tool to create transects from the baseline so they intersect shorelines.
• Provide required parameters, including:
  • Baseline layer
  • Shoreline layer
  • Spacing (example shown: 50 m)
  • Length (how far transects extend from the baseline so they intersect all shorelines)
  • Smoothing distance:
    • Controls transect behavior along curved coasts.
    • Must be chosen based on the study site; example shown: 250
  • Metadata:
    • Presenter emphasizes filling this in, even if not done in the demo.
• Output check:
  • Ensure transects extend across all shoreline dates.
  • Verify transects are not incorrectly overlapping (especially near curves)—they may come close but should not overlap.

5) Calculate Shoreline Change Rates (Calculate Rates Tool)

After generating transects:

• Use the calculate rates tool to compute shoreline movement between dated shoreline positions.
• Confirm setup matches the shoreline set:
  • Baseline layer
  • Shoreline layer(s)
  • Transect layer
• Ensure DSAS uses all shoreline dates:
  • Dated shorelines are represented by different positions; the presenter notes colors may not make this obvious at first glance.
• Key calculation choices:
  • Select an appropriate statistic. Example used:
    • Endpoint rate
      • Defined as: distance between the oldest and newest shoreline divided by the time span (years/lapse years)
  • Set confidence level:
    • Example used: 95%
• Output check:
  • Confirm the calculated layers and classifications are added correctly.

6) Interpret Outputs (End Products)

Main interpretation output:

• A transect-based change layer with:
  • Red = erosion
  • Yellow = neutral / little change (described range: about −0.25 m to +0.25 m)
  • Blue = deposition

Another key end product:

• A summary report including:
  • Transect dates
  • Thresholds and counts (e.g., number of transects)
  • Confidence interval percent
  • Uncertainty value used
  • Transect spacing and smoothing
  • Coordinate system
  • Rate statistics for each transect

Example statistic from the demo:

• About 71% accreting (deposition)
• About 25% eroding

Sources / Speakers Featured (Identified)

• Speaker: Unnamed presenter (no name given in subtitles)
• Source mentioned: USGS (United States Geological Survey) — creator of DSAS
• Software/tool sources mentioned:
  • ArcMap (not integrated in DSAS v6; DSAS is moving away from it)
  • ArcGIS Pro (future focus for DSAS integration)
• Data source: USGS-provided DSAS sample data (used for the demo)