Appendix C β€” Analysis Process and Tool Dependencies

Overview

This page provides a visual guide to the FluvialGeomorph toolbox analysis workflow, showing the order of operations and dependencies between tools.

TipHow to Use
  • Hover over any tool card to see a description
  • Click on a tool card to view its source code on GitHub
  • Scroll horizontally within each phase to see all tools
  • Tools are organized by analysis phase from left to right

Critical Thinking in FluvialGeomorph Analysis

WarningπŸ€” Think Before You Click

Valley bottom delineation is not a push-button analysis. Success requires careful consideration of your landscape, data quality, and analytical goals before running any tools. This workflow emphasizes critical spatial thinking at every step.

Key Questions to Consider Throughout:

  • Does your watershed boundary accurately represent the hydrologic unit?
  • Are there edge effects or artifacts from the delineation process?
  • Do you need to buffer or expand the boundary for context?
  • How do upstream conditions influence your study area?
  • Is the resolution appropriate for your stream scale?
  • What artifacts exist (pits, flat areas, bridges, culverts)?
  • Is vertical accuracy sufficient for subtle geomorphic features?
  • Do you need to condition the DEM (breach, fill sinks)?
  • When was the LiDAR collected? Has the landscape changed?
  • Using existing mapped streams vs. deriving from DEM?
  • If mapped: Are they accurate? Complete? At appropriate scale?
  • If derived: What flow accumulation threshold represents actual channels?
  • How do you handle intermittent vs. perennial streams?
  • Does the network match what you see in aerial imagery?
  • What defines β€œvalley bottom” in your landscape?
  • Floodplain? Terrace? Active channel migration zone?
  • How wide should the valley be in different stream orders?
  • Are you mapping geomorphic features or regulatory boundaries?
  • What time scale are you considering (modern, Holocene, Pleistocene)?

Remember: The tools execute your decisions. Your expertise in geomorphology, hydrology, and local conditions determines the quality of the results. Validate, iterate, and document your reasoning.

Interactive Workflow Diagram

Phase 1: Data Import & Preparation

LiDAR Processing

LAS Dataset to Raster

ArcGIS Pro

Converts LAS point cloud data to raster DEM

β†’

Mosaic to New Raster

ArcGIS Pro

Mosaics multiple DEM tiles into single raster (if needed)

β†’

Clip Raster

ArcGIS Pro

Clips DEM to study area extent

β†’

Project Raster

ArcGIS Pro

Projects raster to different coordinate system if needed for alignment

Field Data Import

ImportThalweg

toolbox

Imports thalweg survey data into the geodatabase

β†’

ImportFieldXS

toolbox

Imports field cross section survey data

β†’

DEMFromField

toolbox

Creates a DEM from field survey points (alternative to LiDAR)

Phase 2: Geomorphic Analysis

Geomorphic Analysis

HydroDEM

toolbox

Creates a hydrologically conditioned DEM - foundation for flow analysis

β†’

Flow Direction

ArcGIS Pro

Creates flow direction raster (D8 or D-Infinity) - foundation for all flow analyses

β†’

Flow Accumulation

toolbox

Calculates upstream contributing area - used for stream network delineation

β†’

Slope

ArcGIS Pro

Gradient analysis - critical for identifying valley breaks and channel confinement

β†’

REM

toolbox

Relative Elevation Model - removes elevation trend to highlight floodplains and terraces

β†’

TPI

ArcGIS Pro

Topographic Position Index - identifies ridges, valleys, and flat areas

Phase 3: Valley Bottom Delineation

Valley Bottom Delineation

Stream Network Creation

ArcGIS Pro

Raster Calculator or Con tool to threshold flow accumulation - creates binary stream/non-stream raster

β†’

Euclidean Distance

ArcGIS Pro

Measures distance from any cell to nearest stream - helps define lateral valley extent

β†’

Raster Calculator

ArcGIS Pro

Combine slope, REM, distance, TPI using logical criteria - iterative refinement based on visual assessment

β†’

Raster to Polygon

ArcGIS Pro

Converts final valley bottom raster to vector - allows for manual editing and attribution

β†’

Manual Editing

ArcGIS Pro

Remove isolated pixels, adjust boundaries based on aerial imagery or field knowledge, add attributes

Phase 4: Confinement Analysis

Confinement Analysis

Valley Width Measurement

ArcGIS Pro

Transects perpendicular to stream centerline - calculate width at regular intervals

β†’

Confinement Ratio

Analysis

Valley width / Channel width - Confined (<4:1), Partly Confined (4-10:1), Unconfined (>10:1)

β†’

Lateral Confinement

ArcGIS Pro

Buffer analysis showing where valley margins constrain channel - identifies confined vs. unconfined reaches

Phase 5: Stream Network

Stream Network

StreamNetwork

toolbox

Delineates stream network from flow accumulation

β†’

StreamNetworkPoints

toolbox

Creates points along stream network

β†’

Watersheds

toolbox

Delineates watersheds for stream segments

Phase 6: Flowline

Flowline

Flowline

toolbox

Creates stream flowline centerline

β†’

FlowlineThalweg

toolbox

Creates flowline from thalweg survey

β†’

FlowlinePoints

toolbox

Creates regularly spaced points along flowline

Phase 7: Water Surface & Channel

Water Surface & Channel

WaterSurfaceExtent

toolbox

Delineates water surface extent from DEM

β†’

ChannelSlope

toolbox

Calculates channel slope from DEM

β†’

Centerline

toolbox

Creates channel centerline from banklines

Phase 8: Cross Sections

Cross Sections

XSLayout

toolbox

Creates cross section layout lines

β†’

XSField

toolbox

Creates cross sections from field survey data

β†’

XSWatershedArea

toolbox

Calculates watershed area at each cross section

β†’

XSRiverPosition

toolbox

Assigns river position to cross section points

β†’

XSResequence

toolbox

Resequences cross section numbering

Phase 9: Cross Section Points

Cross Section Points

XSPoints

toolbox

Creates cross section points from lines

β†’

XSPoints_Classify

toolbox

Classifies cross section points by position

β†’

BanklinePoints

toolbox

Creates points along banklines

β†’

XSAssignLoops

toolbox

Assigns loop identifiers to cross sections

Phase 10: XS Analysis (R)

XS Analysis (R)

XSDimensions

R

Calculates cross section dimensions

β†’

XSDimensions (alt)

R

Alternative XS dimensions calculation

β†’

XSPlanform

R

Analyzes cross section planform geometry

Phase 11: Hydraulic Modeling

Hydraulic Modeling

XS_RAS_WaterSurface

toolbox

Extracts water surface from HEC-RAS results

Phase 12: Additional Analysis

Additional Analysis

Gradient

R

Calculates stream gradient

β†’

Point_Landcover

toolbox

Extracts landcover data at point locations

Tool Reference Table

Phase Tool Package Purpose Inputs Outputs Dependencies
Phase 1: Data Import & Preparation
1 LAS Dataset to Raster ArcGIS Pro Convert LAS to DEM LAS files DEM raster None
1 Mosaic to New Raster ArcGIS Pro Mosaic DEM tiles Multiple DEMs Mosaicked DEM LAS to Raster
1 Clip Raster ArcGIS Pro Clip DEM to extent DEM, polygon Clipped DEM Mosaic
1 Project Raster ArcGIS Pro Project coordinate system DEM Projected DEM Clip
1 ImportThalweg toolbox Import thalweg survey data Survey data Thalweg features None
1 ImportFieldXS toolbox Import field XS survey Survey data XS features None
1 DEMFromField toolbox Create DEM from field data Survey points DEM raster Field survey
Phase 2: Geomorphic Analysis
2 HydroDEM toolbox Create hydro-conditioned DEM DEM Hydro DEM DEM
2 Flow Direction ArcGIS Pro Calculate flow direction Hydro DEM Flow direction raster HydroDEM
2 Flow Accumulation toolbox Calculate drainage area Flow direction Contributing area Flow Direction
2 Slope ArcGIS Pro Calculate slope DEM Slope raster DEM
2 REM toolbox Relative Elevation Model DEM, flowline REM raster HydroDEM
2 TPI ArcGIS Pro Topographic Position Index DEM TPI raster DEM
Phase 3: Valley Bottom Delineation
3 Stream Network Creation ArcGIS Pro Threshold flow accumulation Flow accumulation Stream raster Flow Accumulation
3 Euclidean Distance ArcGIS Pro Distance from streams Stream raster Distance raster Stream Network
3 Raster Calculator ArcGIS Pro Combine geomorphic criteria Slope, REM, Distance, TPI Valley bottom raster Multiple inputs
3 Raster to Polygon ArcGIS Pro Convert to vector Valley bottom raster Valley polygon Raster Calculator
3 Manual Editing ArcGIS Pro Refine boundaries Valley polygon Final valley bottom Raster to Polygon
Phase 4: Confinement Analysis
4 Valley Width Measurement ArcGIS Pro Measure valley width Valley polygon, centerline Width transects Valley polygon
4 Confinement Ratio Analysis Calculate confinement Valley width, channel width Confinement values Width measurements
4 Lateral Confinement ArcGIS Pro Map confinement zones Valley polygon, channel Confinement polygons Valley polygon
Phase 5: Stream Network
5 StreamNetwork toolbox Delineate stream network Flow accumulation Stream lines ContributingArea
5 StreamNetworkPoints toolbox Create stream points Stream network Stream points StreamNetwork
5 Watersheds toolbox Delineate watersheds Flow direction, points Watershed polygons ContributingArea
Phase 6: Flowline
6 Flowline toolbox Create flowline Stream network Flowline StreamNetwork
6 FlowlineThalweg toolbox Flowline from thalweg Thalweg survey Flowline ImportThalweg
6 FlowlinePoints toolbox Create flowline points Flowline, spacing Flowline points Flowline
Phase 7: Water Surface & Channel
7 WaterSurfaceExtent toolbox Delineate water surface DEM Water surface polygon HydroDEM
7 ChannelSlope toolbox Calculate channel slope DEM, flowline Slope values Flowline
7 Centerline toolbox Create centerline Banklines Centerline Banklines
Phase 8: Cross Sections
8 XSLayout toolbox Create XS layout Flowline, spacing XS lines Flowline
8 XSField toolbox XS from field survey Field survey XS lines ImportFieldXS
8 XSWatershedArea toolbox XS watershed area XS lines, watersheds Area values XSLayout, Watersheds
8 XSRiverPosition toolbox Assign river position XS points Position attributes XSPoints
8 XSResequence toolbox Resequence XS XS lines Resequenced XS XSLayout
Phase 9: Cross Section Points
9 XSPoints toolbox Create XS points XS lines, DEM XS points XSLayout
9 XSPoints_Classify toolbox Classify XS points XS points Classified points XSPoints
9 BanklinePoints toolbox Create bankline points Banklines Bankline points Banklines
9 XSAssignLoops toolbox Assign loop IDs XS lines, loops Loop attributes XSLayout
Phase 10: XS Analysis (R)
10 XSDimensions R Calculate XS dimensions XS points Dimensions XSRiverPosition
10 XSDimensions (alt) R Calculate XS dimensions XS points Dimensions XSRiverPosition
10 XSPlanform R Analyze XS planform XS points Planform metrics XSDimensions
Phase 11: Hydraulic Modeling
11 XS_RAS_WaterSurface toolbox Extract RAS water surface HEC-RAS results Water surface HEC-RAS model
Phase 12: Additional Analysis
12 Gradient R Calculate gradient Profile points Gradient values FlowlinePoints
12 Point_Landcover toolbox Extract landcover Points, landcover raster Landcover attributes Points
Note

Valley Bottom Workflow Focus This workflow emphasizes critical thinking before tool execution. Phase 1 includes LiDAR processing to create the DEM and field data import tools. Phase 2 generates the geomorphic datasets (Flow Direction, Flow Accumulation, Slope, REM, TPI) that are then combined in Phase 3 to delineate valley bottoms. Phase 4 analyzes channel confinement within the delineated valley. Key Change: DetrendDEM is now called REM (Relative Elevation Model) to better reflect its purpose of showing relative topographic position.

Key Considerations

  • Visual comparison with aerial imagery
  • Field validation of key reaches
  • Check for systematic errors
  • Document assumptions and decisions
  • Valley bottom delineation is iterative
  • Adjust thresholds based on local conditions
  • Test sensitivity to parameter changes
  • Validate against known geomorphic features
  • DEM resolution affects feature detection
  • Stream order influences valley width
  • Adjust analysis parameters by stream size
  • Consider multi-scale approaches