Cliff Feature Delineation Tool and Baseline Builder Tool, 

Version 1.0 User Guide

Open-File Report 2020–1070

U.S. Department of the Interior

U.S. Geological Survey
Cover: Digital three-dimensional rendering of the coastal cliffs around Point Dume in Malibu, California. Cliff feature outputs from the Cliff Feature Delineation Tool 

are shown to conceptually display the cliff delineation process, including cross-shore transects (green), the cliff top line (red), the cliff toe line (blue), and subsidiary 

cliff features (orange). Base-map data credits: USGS, National Agriculture Imagery Program, NOAA, ESRI, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/

Airbus DS, USDA, AeroGRID, IGN, and the GIS User Community.
Cliff Feature Delineation Tool and Baseline Builder Tool, 

Version 1.0 User Guide

By Alexander C. Seymour, Cheryl J. Hapke, and Jonathan Warrick 

Open-File Report 2020–1070

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly, Director

U.S. Geological Survey, Reston, Virginia: 2020

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment—visit

https://www.usgs.gov/ or call 1–888–ASK–USGS (1–888–275–8747).

For an overview of USGS information products, including maps, imagery, and publications,

visit https://www.usgs.gov/pubprod/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply

endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also may

contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items

must be secured from the copyright owner.

Suggested citation:

Seymour, A.C., Hapke, C.J., and Warrick, J., 2020, Cliff Feature Delineation Tool and Baseline Builder 

version 1.0 user guide: U.S. Geological Survey Open File Report 2020–1070, 54 p., 

https://doi.org/10.3133/ofr20201070.

Associated software release for this publication: 

Seymour, A.C., Hapke, C.J., and Warrick, J., 2020, Cliff Feature Delineation Tool and Baseline Builder 

version 1.0: U.S. Geological Survey software release, https://doi.org/10.5066/P9UKW7PO.

ISSN 2331-1258 (online)
iii

Contents

Abstract ...........................................................................................................................................................1

1. Introduction..................................................................................................................................................1

1.1 Defining the Cliff Feature Delineation Tool............................................................................................2

1.2 Tool Logic Overview..............................................................................................................................2

1.3 Cliff Feature Delineation at the U.S. Geological Survey .......................................................................3

1.4 Experimental Software Use Considerations..........................................................................................4

2. Algorithm Logic............................................................................................................................................4

2.1 Generating Cross-Shore Transects ......................................................................................................5

2.2 Extracting Surface Information Across Cross-Shore Transects ............................................................5

2.3 Locating Cliff Tops, Midpoints, and Basic Toes .....................................................................................7

2.4 Refining the Cliff Toe Location ..............................................................................................................7

2.5 Subsidiary Feature Delineation...........................................................................................................10

2.6 Vectorizing Cliff Features ....................................................................................................................11

2.7 Cleaning the Scratch Workspace........................................................................................................13

3. Installation .................................................................................................................................................14

3.1 System Requirements.........................................................................................................................14

3.2 Unpacking the Tool..............................................................................................................................14

3.3 Working Directory Structure................................................................................................................16

4. Input Data Requirements...........................................................................................................................17

4.1 The Raster Digital Elevation Model.....................................................................................................17

4.2 The Offshore Baseline ........................................................................................................................19

5. Running the Tool........................................................................................................................................20

5.1 Initiating a Cliff Feature Delineation Tool Run.....................................................................................20

5.2 Explanation of Tool Inputs and Starting Parameters...........................................................................21

5.2.1 Offshore Baseline Parameter .......................................................................................................21

5.2.2 Smooth Baseline Parameter.........................................................................................................21

5.2.3 Baseline Smoothing Tolerance .....................................................................................................21

5.2.4 Raster DEM Parameter ................................................................................................................21

5.2.5 Landward Distance and Seaward Distance Parameters ..............................................................21

5.2.6 Transect Interval Parameter .........................................................................................................22

5.2.7 Delineation Mode Parameter........................................................................................................22

5.2.8 Refinement Method Parameter ....................................................................................................23

5.2.9 High Pass Threshold Parameter...................................................................................................23

5.2.10 Subsidiary Feature Delineation Parameter.................................................................................23

5.2.11 Kernel Size Parameter................................................................................................................24

5.2.12 Output Smoothing Tolerance Parameter ....................................................................................24

5.2.13 Output Cleanup Parameter.........................................................................................................24

5.2.14 Series Name Parameter.............................................................................................................25

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline.....................................................26

6.1 Baseline Builder Tool Overview...........................................................................................................26

6.2 Running the Baseline Builder Tool ......................................................................................................28

6.3 Explanation of Baseline Builder Tool Starting Parameters..................................................................29

6.3.1 Input DEM Description..................................................................................................................29
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Figures

1. An elevation profile showing the upward sloping chord line projected across each transect............ 3

2. Maps showing the step-by-step process used by the algorithm to generate cross-shore transects . 6

3. Cliff elevation profiles showing corresponding high-pass profiles and surface plane intersections 

along a cross shore transect ............................................................................................................. 8

4. A surface profile showing chord line length as a potential source of cliff feature misclassification ... 9

5. Surface profiles showing examples of potential errors during high pass method toe refinement ... 10

6. A surface profile showing the possible outputs using the Cliff Feature Delineation Tool................. 11

7. Images showing selected outputs from the Cliff Feature Delineation Tool superimposed on a 

digital elevation model..................................................................................................................... 12

8. An image showing all possible outputs of the Cliff Feature Delineation Tool shown for a short 

stretch of coast in the ArcScene 3D format..................................................................................... 14

9. Instructions for setting up the Cliff Feature Delineation Tool and companion Baseline Builder 

Tool within the ArcGIS toolbox......................................................................................................... 15

10. Images showing the processing steps taken by the Cliff Feature Delineation Tool to cast cross 

shore transects................................................................................................................................ 18

11. Instructions for initiating a Cliff Feature Delineation Tool run .......................................................... 20

12. An image showing the cliff top line, cross-shore transects, and flagged cutback transects............ 25

13. Images showing the processing steps taken by the Baseline Builder Tool to construct alongshore 

baselines adjacent to cliff ................................................................................................................ 27

14. Instructions for running the Baseline Builder Tool ........................................................................... 28

15. An image showing offshore baselines generated with different smoothing tolerances using the 

Baseline Builder Tool....................................................................................................................... 31

6.3.2 Cliff Height Setting........................................................................................................................30

6.3.3 Neighborhood Setting...................................................................................................................30

6.3.4 Baseline Distance Input................................................................................................................30

6.3.5 Smoothing Tolerance Input...........................................................................................................30

6.3.6 Filter Type Parameter...................................................................................................................30

6.3.7 Maximum Elevation Threshold Setting .........................................................................................30

6.3.8 Minimum Elevation Threshold Setting ..........................................................................................31

6.3.9 Output Name ................................................................................................................................31

6.4 Reviewing Baseline Builder Tool Outputs ...........................................................................................32

6.5 Manually Digitizing an Offshore Baseline............................................................................................37

7. Visualizing and Reviewing Cliff Feature Delineation Tool Outputs ............................................................40

7.1 Visualizing Features in ArcScene........................................................................................................41

7.2 Modifying Features in ArcScene .........................................................................................................42

7.3 Visualizing Features in ArcMap...........................................................................................................45

7.4 Exporting Features to Text Tables.......................................................................................................49

7.5 Error Logs ...........................................................................................................................................50

7.6 Intermediate Outputs ..........................................................................................................................50

Acknowledgments .........................................................................................................................................50

References Cited...........................................................................................................................................51

Glossary ........................................................................................................................................................53
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

16. Instructions for editing the Baseline Builder Tool output for use as an offshore baseline................ 32

17. Instructions for manually digitizing a baseline, with the Baseline Builder Tool output used as a digitizing guide ...................................................................................................................................... 37

18. An image showing the ArcScene “Table of Contents” and “Symbol Selector,” which can be used to 

change the symbology of output shapefiles .................................................................................... 41

19. An image showing the key navigation tools for modifying the camera view in ArcScene, along 

with selected cliff feature outputs .................................................................................................... 42

20. Instructions for editing any cliff feature line in ArcScene ................................................................. 42

21. Instructions for graphing cross-shore transects and cliff feature points using ArcGIS Desktop ...... 46
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Conversion Factors

International System of Units to U.S. customary units

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd) 

kilometer (km) 0.6214 mile (mi)

kilometer (km) 0.5400 mile, nautical (nmi)

Datum

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).

Abbreviations 

2D two dimensional

3D three-dimensional

CFDT Cliff Feature Delineation Tool

.csv comma-separated values file

DEM digital elevation model

DSAS Digital Shoreline Analysis System

DSM digital surface model

.geotiff Georeferenced Tagged Image File Format

GIS geographic information system

km kilometer

m meter

NAVD 88 North American Vertical Datum of 1988

sUAS small unmanned aerial system

TIN triangular irregular network

.txt text file

USGS U.S. Geological Survey

UTM Universal Transverse Mercator

.zip lossless data compression archive file
Cliff Feature Delineation Tool and Baseline Builder Tool, 

Version 1.0 User Guide

By Alexander C. Seymour, Cheryl J. Hapke, and Jonathan Warrick 

Abstract

Coastal cliffs constitute 80 percent of the world’s coastline, with seacliffs fronting a large 

proportion of the U.S. West Coast shoreline, particularly in California. Erosion of coastal cliffs 

can threaten infrastructure and human life, yet the spatial and temporal scope of cliff studies have 

been limited by cumbersome traditional methods that rely on the manual interpretation of seacliff features—especially seacliff toes and top edges. The Cliff Feature Delineation Tool (CFDT) 

and the Baseline Builder Tool are designed to increase the efficiency of deriving seacliff features 

from remote sensing datasets by utilizing an automated, quantitative approach that eliminates 

traditional interpretive methods and ensures reproducibility. This document functions as a user 

guide for operating the Cliff Feature Delineation Tool and Baseline Builder Tool and includes a 

walkthrough of data-visualization and data-review workflows for the tools’ three-dimensional 

(3D) cliff feature outputs. Also included is a brief overview of cliff feature delineation at the 

U.S. Geological Survey (USGS) and a detailed description of the tools’ algorithmic logic.

1. Introduction

Coastal cliffs front approximately 80 percent of the world’s shorelines (Emery and Kuhn, 

1982), including long stretches of the U.S. coast where 1,300 kilometers (km) of seacliffs in 

California alone are in an erosive condition (Griggs and Patsch, 2004). Erosion in these areas 

threatens valuable real estate, undermines tourist economies (Hapke and Reid, 2007), and can 

directly endanger human life (Bird, 1994). Despite the widespread occurrence of seacliffs and 

coastal bluffs, the large spatial extent of coastal cliff coverage restricts the frequency of coastal 

change analysis by traditional, manual methods, which are time-consuming and have limited 

repeatability due to their reliance on human interpre tation of the imagery (Rutzinger and others, 2012; Ruggiero and others, 2013). Combined with the increasing availability of large scale, 

high-accuracy, high-resolution lidar and photogrammetric topographic datasets, seacliff change 

research can benefit greatly from automated image analysis and computer vision processes 

that map the morphological features of cliff environments. Outputs from automated algorithms 

can help validate predictive cliff-erosion models (Hapke and Plant, 2010) against a quantitative benchmark or help fill spatial and temporal data gaps that are increasingly constrained by 

manual analysis methods in an era of “big data.” To this end, the Cliff Feature Delineation Tool

(CFDT) and Baseline Builder Tool described in this report are designed to speed the spatial 

delineation of cliff morphology while removing the potential for variable human interpretation, 

ultimately making outputs more repeatable.
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

1.1 Defining the Cliff Feature Delineation Tool

The CFDT is an automated computer-vision application designed to generate 3D line 

features representing the seacliff top, midpoint, and toe on high-relief coastal cliffs. The program 

also delineates 3D points on concavities and convexities across the cliff face (termed “subsidiary 

features”), which may represent talus deposits, secondary cliff tops, and secondary cliff toes. The 

tool package includes algorithms for automatically generating alongshore baselines (the Baseline 

Builder Tool), determining landward or seaward direction, and casting cross-shore transects with 

little or no user intervention. The application is freely available as a script tool for Esri ArcGIS 

Desktop version 10.6 and 10.7; generated 3D shapefiles can be reviewed in ArcGIS, converted to 

traditional cross-shore elevation profiles, exported as text tables, or manipulated in a 3D viewing environment such as Esri ArcScene.1 After cliff feature lines from two or more timepoints 

are delineated, line outputs can be combined with the Digital Shoreline Analysis System (DSAS; 

Himmelstoss, and others, 2018) to determine rates of cliff-top, midline, and toe migration in 

the same way that an analysis is conducted on a shoreline timeseries. This document serves as a 

guide for installing and operating the CFDT, as well as interpreting and conducting a data review 

on its outputs. Additionally, this guide includes a detailed description of CFDT algorithm logic 

and an overview of recent predecessors in the field of cliff feature delineation.

1.2 Tool Logic Overview

The CFDT uses two data inputs to generate cliff feature delineations: a raster digital 

elevation model ([DEM], derived from lidar or photogrammetry) and an offshore baseline automatically generated by the companion Baseline Builder Tool or digitized manually by the user. 

The core function of the CFDT is based on multiple cross-shore transects generated perpendicular to the offshore baseline input at a regular interval specified by the user. Cross-shore transects 

extract the DEM profile of the underlying cliff into a tabular format, where an algorithm casts 

a first-order polynomial “chord line” between the start and end of each cross-shore transect, 

representing an upward-sloping plane intersecting the cliff face (fig. 1) (Palaseanu-Lovejoy and 

others, 2016). Estimates of the cliff top, cliff toe, and cliff midpoint positions on each transect 

are determined by the maximum vertical distance between the plane and the profile surface. Toe 

position refinement can be conducted through two methods: value thresholding of a high-passfiltered slope raster derived from the input DEM or the filtering of convexities on the lower half 

of the cliff. Subsidiary features are flagged by casting additional chord lines on the upper and 

lower half of the cliff and executing additional concavity-convexity analysis. Top, toe, midline, 

and subsidiary feature estimates for each cross-shore transect are reprojected as shapefiles and 

converted into 3D line and point features using ArcGIS linear referencing.

As previously mentioned, the companion Baseline Builder Tool is responsible for automatically generating offshore baselines adjacent to the seacliffs represented in the DEM, satisfying a required input for the CFDT that would otherwise require manual digitization. This tool 

integrates user-specified height and area parameters into a spatial kernel, which scans the DEM 

1Although the footnotes in this report link to information about tools in Esri ArcGIS Desktop 

version 10.6, information on the Esri ArcGIS Desktop version 10.7 tools can be found by following the links given in the footnotes of this report for the individual version 10.6 tools and selecting “10.7” on the “Other versions” dropdown list found on the page for each tool.
3

1. Introduction

for relief features. Once classified, the relief features are vectorized, buffered, smoothed, and 

then filtered by elevation statistics so that only line segments seaward of relief features near sea 

level are represented in the final baseline.

1.3 Cliff Feature Delineation at the U.S. Geological Survey

The CFDT was preceded by a workflow developed by Palaseanu-Lovejoy and others (2016) that was designed for seacliff feature delineation and bluff erosion analysis in the 

R programming environment. The workflow established the use of chord line projection across 

cross-shore transect elevation profiles, using the greatest chord line to elevation profile difference 

to determine cliff top and toe features. This process also included profile inflection analysis to 

identify cliffs as concave, convex, or complex. The Palaseanu-Lovejoy and others (2016) algorithm, along with subsequent modifications to the basic chord line method (Hapke and others, 

2018), exist within a larger body of algorithm-based cliff delineation work that includes kernelbased DEM analysis (Richter and others, 2013), polynomial-based identification of surface-plane 

breakpoints (Briese, 2004), as well as image classification applied to satellite imagery (Di and 

others, 2003). In this context, the Palaseanu-Lovejoy and others (2016) algorithm provided a 

semiautomated solution for cliff feature delineation independent of surface slope, and it is, therefore, more robust when applied to varied or complex cliff morphologies.

Subsequent coastal-bluff erosion research within the USGS has been split between 

analyzing raw 3D point-cloud models (Warrick and others 2017; Warrick and others 2019) and 

improving upon the Palaseanu-Lovejoy and others (2016) algorithm for application with twodimensional (2D) DEMs (Hapke and others, 2018). Additions to the Palaseanu-Lovejoy and others (2016) technique have included cliff midpoint delineation to help discriminate between cliff 

changes driven by marine and terrestrial processes, along with kernel-based slope statistics and 

secondary chord lines (Hapke and others, 2018) to refine candidates for cliff top and toe locations. These secondary delineations may help refine or improve the accuracy of toe delineation 

compared with Palaseanu-Lovejoy and others (2016) and provide the analyst with guidance to 

manually vectorize areas where cliff position estimates are erroneous.

Figure 1. An elevation profile showing the upward sloping chord line projected across each transect, 

specifically developed by Palaseanu-Lovejoy and others (2016) for cliff feature delineation applications. 

NAVD 88, North American Vertical Datum of 1988.

-5

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 45 50 55 60

Elevation, in meters NAVD88

Transect distance, in meters from seaward extent

Chord line

Elevation profile

re 1
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

The CFDT uses a hybrid approach that synthesizes the Palaseanu-Lovejoy and others 

(2016) and Hapke and others (2018) algorithms with additional processing modifications, building on the fundamental Palaseanu-Lovejoy chord line method. Previous attempts at cliff feature 

delineation required a preexisting shoreline vector, or integrated DEM information only after 

cross-shore transects or baselines had been digitized or cast by the user, with inconsistencies 

in manual digitization providing opportunities for error accumulation. The CFDT analyzes the 

DEM during the automated generation of an offshore baseline and cross-shore transects, resulting in consistent distances between the baseline and cliff face, in addition to the establishment of 

landward-seaward orientation without user intervention. The tool includes 3D data review functionality, two toe-location refinement methods (one based on an edge-enhancement filter and the 

other on a slope-analysis kernel), a method for delineating subsidiary features on the cliff face, 

options for processing across a range of input DEM resolutions, and recursive error detection on 

the polyline outputs of cliff top and toe features. Toe refinement methods and subsidiary feature 

delineation can identify talus features and concavities-convexities on the cliff face, and they can 

provide several versions of a cliff toe for a given length of cliff. Because cliff morphology is 

variable and a single method may not optimally characterize all cliff types, an analyst can display 

multiple outputs for an overarching area and choose the one that performs best in a given region.

1.4 Experimental Software Use Considerations

The CFDT is intended for experimental use rather than for immediate use in aiding management decisions. The tool contains multiple methods for delineating primary and subsidiary 

cliff features and this guide contains no quantitative assessment of cliff feature delineation accuracy, either absolute or comparative. One method is based on the logic contained in PalaseanuLovejoy and others (2016), and the accuracy of outputs using this method is likely to be similar 

to the accuracy of the results reported in that study. However, the toe refinement and subsidiary 

feature delineation methods used by this tool diverge significantly from those of PalaseanuLovejoy and others (2016). Furthermore, a qualitative investigation of initial results suggests 

that the comparative performance of delineation methods is influenced by cliff morphology and 

foreshore slope, which are discussed further in sections 2.3 and 2.4 of this guide. CFDT users 

should employ quality assurance and control procedures before tool outputs are used to inform 

major management decisions, and they should conduct an accuracy assessment with ground-truth 

data when possible. Any use of trade, firm, or product names in this manual is for descriptive 

purposes only and does not imply endorsement by the U.S. Government.

2. Algorithm Logic

The delineation workflow begins after a user imports a raster DEM and an offshore 

baseline, with the baseline located just offshore of the cliff, generated either using the Baseline 

Builder Tool or through manual digitization (described in section 6). The user then populates the 

setting options in the tool dialog box and initiates the processing run (described in section 5). The 

sections below describe the logical ruleset governing cliff feature delineation in the algorithm. 

Explanation of the specific Python functions used to construct the algorithm logic can be found 

in the inline comments annotating each function in the tool’s script file. 
5

2. Algorithm Logic

2.1 Generating Cross-Shore Transects

The CFDT must first determine the correct landward or seaward orientation, relative to 

the offshore baseline, in order to cast cross-shore transects and extract elevation profiles of the 

seacliff. In this application, cross-shore transects are most effective when they are extended in 

the landward and seaward directions from the input baseline, with the landward component necessarily longer. Additionally, several challenges are present. First, the angle bearing of the baseline can vary widely across a given study area. Second, default topological rules that enforce the 

start or end of digitized lines do not account for topographic context. Lastly, single-orientation 

parameters input by a user are unlikely to result in accurate transect casting directions across the 

whole of a study area with varying shoreline orientations. The algorithm, to address these challenges, automatically determines the landward and seaward orientation on a segment by segment 

basis using the input DEM. Given an offshore baseline input (generated by either the user or the 

Baseline Builder Tool detailed in section 6), the algorithm establishes a buffer on the right and 

left sides of each baseline segment2 and records the mean DEM value within the buffer. For each 

left-right buffer pair, the buffer with the highest mean elevation indicates the landward direction 

(fig. 2A).

Next, CFDT uses a feature in the ArcMap library called “Linear Referencing” (“Create 

Route” and “Create Route Event Layer” tools, Esri ArcMap) to project a framework of points 

representing the start and end vertices of the seaward and landward components of transects cast 

perpendicular to the baseline. Points for both seaward and landward transect distances are initially projected on both sides of the baseline (fig. 2B) but are then spatially filtered by the buffer 

polygons (fig. 2C). This filtering step enforces the landward-seaward orientation of the points, 

with cross-shore transect polylines then generated from the filtered points (“Point to Line” tool, 

Esri ArcMap) (fig. 2D). The linear referencing and orientation workflow also allow specific locations along a given cross-shore transect to be referenced relative to the distance (in meters [m]) 

from the seaward start of a transect. Later steps in the algorithm, which identify cliff features, 

flag the feature locations using this relative distance metric.3 Transects are assigned unique identification numbers in their shapefile attribute table that represent cross-shore transect locations, 

in meters, along the full offshore baseline. The user specifies the spacing between transects (see 

section 5.2.6 for information on how to choose a transect interval).

2.2 Extracting Surface Information Across Cross-Shore Transects

After cross-shore transects are cast, surface information derived from the DEM is extracted along the length of each cross-shore transect and exported in tabular format. The first 

data element is an elevation profile interpolated (by bilinear method) directly from the DEM at 

an interval matching its cell resolution (“Stack Profile” tool, Esri ArcMap). A linear equation is 

appended to the row entries for each cross-shore transect, representing each transect’s primary 

chord line. The chord line construction follows the same logic as Palaseanu-Lovejoy and others (2016); the polynomial is formed by connecting the most seaward xy coordinate on the elevation profile with the most landward xy coordinate (fig. 1). At this stage, any transect that lacks 

2These segments are defined as continuous, unbroken polylines.

3For more information on linear referencing see https://desktop.arcgis.com/en/arcmap/10.6/

manage-data/linear-referencing/what-is-linear-referencing.htm
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Figure 2. Maps showing the step-by-step process used by the algorithm to generate crossshore transects. Images showing (A) elevation scanning buffers projected from offshore baseline 

segments. These buffers identify the landward (pink) and seaward (blue) orientation adjacent to 

each segment. Only one baseline segment is shown in this example, but a typical processing 

run would include multiple segments. Red box identifies location of images in B, C and D. (B) 

Points representing the start and end vertices of landward and seaward transect components 

before orientation filtering. (C) Seaward and landward points remaining after orientation filtering. 

(D) Cross-shore transects formed from filtered seaward and landward points.

250

Meters

Offshore

baseline

Landward

buffer

Seaward

buffer

Landward

transect

points

Seaward

transect

points

Raster DEM

Meters

High: 35

Low: -5 100

Meters

Seaward 

transect 

start

Landward

transect 

end

A

C

B

D
7

2. Algorithm Logic

elevation data at its start or endpoint is removed from processing, as this indicates that the DEM 

does not encompass the full transect extent.

The second element of extracted data is a tabular high-pass profile used to refine cliff toe 

delineation (fig. 3A). A surface-slope raster is first generated from the DEM (“Slope” tool, Esri 

ArcMap) using a 3x3 cell kernel that calculates the rate of elevation change to derive these data.4

Next, this slope raster is processed by a high-pass filter (“Filter” tool, “High” setting, Esri ArcMap), which applies a modified 3x3-cell Laplace kernel.5 High-pass filters are image-analysis 

operators used to accentuate the edges between value gradients in rasters, with filter outputs 

that are signed, unitless values. In this context, the high-pass filter produces a new raster with 

extreme positive and negative values around the intersection of two planar surfaces (fig. 3B). 

Extreme positive values are on the upper side of the edge, and extreme negative values are on 

the lower side of the edge. Values on the planes separate from the planar intersections remain 

close to zero. The negative values on the high-pass filter raster are tabulated and appended to the 

elevation profile (fig. 3A) (“Stack Profile” tool, Esri ArcMap), with positive values excluded, as 

they are not used later. While this tool uses a bilinear interpolation when it extracts data from 

rasters and changes the high-pass values, the spatial location of local high-pass maxima does not 

change. 

2.3 Locating Cliff Tops, Midpoints, and Basic Toes

Cliff top and basic toe delineation occur using logic similar to that established in 

Palaseanu-Lovejoy and others (2016). For these analyses, the vertical distance between the chord 

line and the surface profile is calculated for every extracted cell (row) along the cross-shore 

transect. The cell entry with the greatest positive difference from the chord line is identified as 

the cliff top, and the entry with the greatest negative vertical distance from the chord line is 

identified as the basic cliff toe (fig. 4). After the cliff top and basic toe are determined, the cliff 

midpoint is flagged by identifying the location on the cross-shore transect between the cliff top 

and basic toe where the surface elevation is closest to half of the cliff height, or:

(1)

The cliff midpoint is useful for distinguishing between physical processes affecting the upper and lower 

halves of cliffs, and it is also used later during cliff toe refinement and subsidiary feature delineation.

2.4 Refining the Cliff Toe Location

The basic chord line distance method described above yields strong position estimates for 

the cliff top and toe when cliffs in a study area are relatively high relief, and cross-shore transect 

lengths can be relatively short. These factors allow for a steeper primary chord line that is more 

likely to have a slope exceeding that of the beach fronting the cliff. However, when cliff faces 

are more gradually sloped or transect distances must be made longer, the basic toe delineation 

may become less accurate. This problem occurs when the slope of the foreshore approaches or 

4For more information on the slope algorithm used in the Esri slope tool, see https://desktop.

arcgis.com/en/arcmap/10.6/tools/spatial-analyst-toolbox/how-slope-works.htm

5For more information on the high pass filter algorithm used in the Esri ArcGIS “Filter” tool, see 

https://desktop.arcgis.com/en/arcmap/10.6/tools/spatial-analyst-toolbox/how-filter-works.htm
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

exceeds the slope of the chord line so that the true cliff toe location has a smaller vertical difference from the chord line than areas of the foreshore (fig. 4). For this reason, when basic toe 

misclassifications occur, they usually generate false positives on the foreshore and occasionally 

on the landward extent of the talus. Because cliff morphology is likely to be variable across a 

study area and it is impractical for a human analyst to optimize cross-shore transect lengths for 

every transect interval, two cliff toe refinement methods that can improve the cliff toe delineation 

automatically, without modifying cross-shore transect length, are included.

First, the “High Pass” method scans the high-pass profile for values that exceed a userspecified threshold (fig. 3A), restricting the processing extent to the cross-shore transect area 

between the basic toe and midpoint. This threshold is a unitless, negative high-pass value ranging from −6 to −50 and defaulting to −25 in the absence of user input. Starting at the basic toe 

and moving toward the midpoint, the first cell along the transect with a value that exceeds (has 

a more extreme negative value than) the high-pass threshold is flagged as the refined cliff toe. If 

the user sets the high-pass threshold closer to zero, the refined toe is classified on surface-plane 

intersections that are less different in slope and usually farther seaward. If the algorithm scans 

the region between the basic toe and midpoint without triggering the threshold, the threshold 

Figure 3. Cliff elevation profiles showing (A) a corresponding high-pass profile along a cross-shore 

transect and (B) variously colored dashed-line representations of rough surface planes occurring along the 

cross-shore transect. High-pass value extrema correspond to surface-plane intersections and are more 

extreme when slope differences between two planes are large and occur over a short horizontal distance. 

NAVD 88, North American Vertical Datum of 1988.

0

5

10

15

20

25

30

35

40

-5

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

High-pass value

Elevation, in meters NAVD88

Transect distance, in meters from seaward extent

Elevation profile

High-pass profile

-5

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Elevation, in meters NAVD88

Transect distance, in meters from seaward extent

Elevation profile

Surface planes

True cliff top-toe

Surface plane representations

A

B

 3
9

2. Algorithm Logic

is revised five units6 closer to zero and the region is rescanned starting from the basic toe. This 

process iterates until the threshold is exceeded or the revised threshold reaches –5, as values less 

extreme than –5 represent profile features too small to be cliff toes. In the latter case, the basic 

toe is accepted as the refined toe. A user-modifiable, downward-revising high-pass threshold 

helps compensate for circumstances where increases in the slope across the cliff toe region are 

subtle. In these situations, the high-pass profile values around the toe may be too low to exceed 

the default threshold (fig. 5A) or may be less extreme than planar intersections higher on the cliff 

face between the basic toe and midpoint (fig. 5B).

Second, the “First Concavity” method identifies the cliff toe by casting a secondary chord 

line formed by a linear function connecting the basic toe and the cliff midpoint and then running 

an analysis kernel across the elevation profile (fig. 6). The analysis kernel is one-dimensional (a 

single row of cells), and the user can modify its size (length in cells). The kernel computes averages of the local surface slope, flagging points where the slope of the surface profile dips below 

and rises above the slope of the secondary chord line within the kernel’s extent, representing a 

concavity on the elevation profile (fig.6). The most seaward flagged cell between basic toe and 

cliff midpoint becomes the refined toe position. If no convexity is found on the lower half of the 

cliff, the refined toe location reverts to the basic toe location. 

Both toe refinement methods are restricted to regions of the cliff between one cell seaward 

of the cliff toe and the cliff midpoint in order to avoid the generation of false positives on other 

shoreline or bathymetric features. When basic toe misclassification occurs, toes are most frequently identified seaward of the true toe, and refinement methods perform best in these situations; an 

accurate basic toe may limit refinement analysis to areas on the cliff face above the cliff toe. Thus, 

when cross-shore transects are short (such as on simple, high-relief cliffs), refined toes may appear 

on the cliff face, and the basic toe delineation may outperform the refined delineation.

6The five-unit interval was selected as a compromise between smaller intervals—smaller intervals require more iterations to classify a cliff feature, which consumes more processing time.

Figure 4. A surface profile showing chord line length as a potential source of cliff feature misclassification.

The differences between the chord line and cliff top-toe predictions (profile to chord line distance maxima) are 

shown for short and long transects. The foreshore slope exceeds the chord line slope for the long transect, and 

as a result, the toe is identified seaward of its true location. In this example, the cliff top position is tolerant of 

variability in the slope of the chord line. NAVD 88, North American Vertical Datum of 1988.

-1

4

9

14

19

24

29

34

0 10 20 30 40 50 60 70 80 90 100 110 120

Elevation, in meters NAVD88

Transect distance, in meters from seaward extent

Long chord line

Short chord line

Profile to long

chord line distance 

Profile to short 

chord line distance 

True cliff top-toe

Foreshore

ure 4
10

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

2.5 Subsidiary Feature Delineation

The cliff top, toe, and midline are not the only features on a cliff that have implications 

for how and why a coastal cliff erodes. Convexities and concavities on a cliff face could indicate 

a break in a slope resulting from differential erosion of the cliff, the talus debris fan, or the intersection of the talus debris fan with the cliff face. To delineate these features, secondary chord 

lines are cast on both the upper and lower halves of the cliff. A linear chord connects the basic 

toe and midpoint, and a separate linear chord connects the midpoint and cliff top (fig. 6). The 

same slope-measurement kernel used for “First Concavity” toe refinement then scans the upper 

and lower portions of the cliff separately. Points are flagged any time the analysis kernel detects 

slopes, across its extent, that dip below and then rise above the given chord line (fig. 6), representing a surface concavity (potentially the intersection of a talus debris fan with the cliff face). 

Points are also flagged when the slope rises above and then falls below the given chord line, 

representing a surface convexity (potentially a differential erosion feature on the cliff face or a 

seaward portion of the talus debris fan). Unlike toe refinement, the kernel scans the full extent of 

the upper and lower halves of the cliff, flagging all surface convexities and concavities detected.

Figure 5. Surface profiles showing examples of potential errors during high pass method toe refinement. Graphs showing (A) elevation and high-pass profiles in circumstances where a default –25 high-pass 

threshold will fail to classify a cliff toe, and (B) another feature on the lower half of the cliff face having 

a more extreme high-pass value than the cliff toe. The high-pass value does not have measured units. 

NAVD 88, North American Vertical Datum of 1988.

0

5

10

15

20

25

30

35

40

45

-5

0

5

10

15

20

25

30

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

High-pass value

Elevation, in meters NAVD88

Transect distance, in meters from seaward extent

Elevation profile

High-pass profile

True cliff top-toe

0

10

20

30

40

50

60

70

80

90

-5

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

High-pass value

Elevation, in meters NAVD88

Transect distance, in meters from seaward extent

Elevation profile

High-pass profile

True cliff top-toe

A

B
11

2. Algorithm Logic

The flagged convexities and concavities are then filtered separately by the vertical distance from their respective chord lines; the convexity with the greatest positive vertical distance 

from the secondary chord line and the concavity with the greatest negative vertical distance are 

selected as subsidiary features. This process occurs for both the upper and lower halves of the 

cliff, resulting in a maximum of four subsidiary features possible on a given transect. For Basic 

Delineation mode, an additional subsidiary feature can be identified on the lower half of the cliff 

to allow for the toe of the talus (or the true cliff toe) to be identified in circumstances where the 

coarse toe is misclassified seaward and fails to capture its true location.

For both “First Concavity” toe refinement and subsidiary feature delineation, the user can 

modify the size of the slope-analysis kernel. The optimal kernel size depends on cliff morphology and the input DEM resolution. Modifying the kernel size can make delineation less likely to 

generate false positives on small slope features that are not explanatory for the scale of study or 

can parameterize a finer-scale kernel for use on high-resolution DEMs. For instance, if an input 

DEM with a 0.1-m cell resolution is used as an input, a 3-cell kernel only evaluates 0.3-m portions of a cliff at a given time—this cross-shore length is unlikely to encompass the extent of a 

significant cliff feature on any but the smallest cliffs and instead represents numerous surface 

deviations that do not represent overarching cliff morphology. However, a 30-cell kernel encompassing a 3-m cross-shore length aggregates slope measurements over a larger area, diminishing 

the influence of slope deviations across small linear distances and correlating measurements with 

larger, more relevant cliff features.

2.6 Vectorizing Cliff Features

In the two previous sections, cliff features were identified in a tabular format. However, 

every cell-row extracted from a cross-shore transect and identified as a cliff feature remains 

referenced to its one-dimensional location on a given cross-shore transect. Thus, all delineated 

features can be reprojected as point-feature shapefiles. A linear referencing operation (“Create 

Route” and “Make Route Event Layer” tools, Esri ArcMap) is used to project point shapefiles, 

Figure 6. A surface profile showing the possible outputs using the Cliff Feature Delineation Tool. Elevation profile with secondary chord lines and subsidiary features shown with the primary chord line and 

primary cliff features, including a basic toe and refined toes. Subsidiary features represent convexities and 

concavities on the cliff face relative to the subsidiary chord lines and could indicate geologic controls on cliff 

morphology. NAVD 88, North American Vertical Datum of 1988.

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80 90 100 110 120

Elevation, in meters NAVD88

Transect distance, in meters from seaward extent

Elevation profile

Primary chord line

Secondary chord line

Primary cliff feature

Secondary cliff feature

1

2

3

5 4

6 7 8

1. Cliff top

2. Convexity (potential differential-erosion feature)

3. Cliff midpoint

4. Concavity (talus and cliff-face intersection)

5. Convexity (seaward portion of talus debris fan)

6. Refined cliff toe (first concavity method)

7. Basic cliff toe

8. Refined cliff toe (high-pass method)

re 6
12

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Figure 7. Images showing (A) linear cliff features constructed alongshore, including a cliff top, cliff midline, cliff toe, and refined cliff toe generated using the “First Concavity” method, and (B) linear cliff feature 

lines converted from point features referenced to a one-dimensional position along a given cross-shore 

transect. DEM, digital elevation model.

150

Meters

Offshore baseline

Cross-shore transects

Cliff-top line

Cliff-mid line

Cliff-toe line

Refined toe (first concavity)

Cliff-mid point

Cliff-top point

Cliff-toe point

Cliff-toe point

Raster DEM

Meters

High: 35

Low: -5

25

Meters

A

B
13

2. Algorithm Logic

which are then converted to lines (“Point to Line” tool, Esri ArcMap) (fig. 7). A separate polyline shapefile is output for the cliff top, midpoint, and toe (or multiple toes if Multi Delineation

mode is selected). Primary cliff features are additionally generated as point shapefiles, along with 

subsidiary features. Cliff feature lines are broken wherever a user leaves gaps after digitizing the 

offshore baseline, and gaps are also left in areas where the feature delineation failed to generate 

valid outputs. For instance, if an error or exception occurs during delineation of the coarse toe, 

midpoint, or top, the algorithm cancels delineation and skips to the next transect because these 

initial delineations are prerequisites for any location refinement or subsidiary feature delineation. 

If offshore baselines were not digitized in accordance with proper protocols (outlined in 

section 6), cliff feature lines might cut back on themselves alongshore. The CFDT checks for 

remaining cutbacks by intersecting cross-shore transects with cliff feature lines and flags transects that cross over a given feature line more than once. Depending on the user-defined settings, 

transects are buffered and either erase underlying transects or simply flag transects where cutbacks occur. It is common to encounter cutback transects around baselines that surround narrow 

headlands or cliffs on shorelines with short alongshore crenulations. 

Once all features are converted to line shapefiles and erroneous sections are removed, all 

cliff feature lines, subsidiary feature points, and cross-shore transects are converted to 3D vectors 

for viewing in 3D visualization software like ArcScene. The input DEM is treated as an elevation 

benchmark over which feature lines and points are interpolated (“Interpolate Shape” tool, “Bilinear” method, Esri ArcMap), resulting in feature lines that conform closely to the DEM surface. 

Importantly, only the z values of the input lines are interpolated—no modification occurs to the 

x or y coordinates of the polyline. For this reason, the cliff midline, which likely falls on the face 

of a high-relief surface, may appear to have a high variance between cross-shore transects as it 

conforms to the face of the cliff between midpoint positions on transects (fig. 8). This is entirely 

normal and is a product of the alongshore resolution of outputs (the Transect Interval chosen by 

the user).

2.7 Cleaning the Scratch Workspace

At several points in the script, the algorithm scans the scratch workspace to delete intermediate files generated during processing. These files can number in the thousands and are associated with route-merging processes when tabular features are converted to shapefiles or with 

erase processes that clean up erroneous sections of cliff feature lines. The algorithm also deletes 

these files if an exception is encountered that prevents the tool from completing its processing 

run. This step is critical; if these files persist after a given tool run, the intermediate outputs left 

in the scratch workspace are integrated into the next tool run, which causes erroneous projected 

feature lines and unexpected gaps in datasets where valid data was erased. For this reason, if the 

computer restarts unexpectedly, or if ArcMap closes unexpectedly before a processing run can 

complete, the user should delete all files remaining in the “Scratch” folder to ensure they are not 

inadvertently integrated into the next batch of outputs.
14

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Figure 8. An image showing all possible outputs of the Cliff Feature Delineation Tool shown for 

a short stretch of coast in the ArcScene 3D format, including the cliff top (red), midline (green), toe 

(blue), refined toe from the high-pass filter method (pink), and refined toe from the first concavity 

method (orange). Cliff point features are shown in colors corresponding to these lines. Subsidiary 

point features are shown as brown points, and cross-shore transects are displayed in dark red. A 

triangular irregular network (TIN) derived from the input raster digital elevation model (DEM) is displayed as the backdrop. 3D, three-dimensional.

3. Installation

3.1 System Requirements

CFDT v1.0 requires the following to run:

1. Microsoft Windows 7 or Windows 10 operating system.

2. ArcGIS Desktop Standard license or higher. This tool was developed for use with ArcGIS 

Desktop version 10.6 and 10.7.

A. ArcGIS Desktop Spatial Analyst and 3D Analyst extensions,

B. ArcGIS Desktop .NET support feature (installed by default), and

C. Microsoft .NET framework of 4.2.2 or later (installed by default).

3.2 Unpacking the Tool

The Cliff Feature Delineation Tool and companion Baseline Builder Tool exist as Python 

scripts within an ArcGIS toolbox, along with a preestablished set of folders in a working directory. Follow the steps in figure 9 to set up the tools for use.

5 meters

Cliff top

Cliff midpoint

Cliff toe (basic)

Cliff toe (first concavity)

Cliff toe (high pass)

Subsidiary feature
15

3. Installation

Software setup steps Visual guidance

1. Download the CFDT .zip folder. Download link: https://doi.org/10.5066/P9UKW7PO

2. Extract the .zip folder to the chosen directory. This directory is where final and 

intermediate outputs are stored and should 

have several gigabytes of free storage space 

available.

3. Open ArcMap.

4. From the main menu, open the “Catalog” 

pane.

5. Click the “Connect to Folder” button in the 

“Catalog” pane, then navigate to the CFDT 

directory extracted in step 2. Select it and 

click “OK.”

6. The CFDT directory should now appear under the “Folder Connections” section of the 

“Catalog” and can be accessed by ArcMap.

Figure 9. Instructions for setting up the Cliff Feature Delineation Tool (CFDT) and companion Baseline 

Builder Tool within the ArcGIS toolbox. .zip, lossless data compression archive file.
16

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

3.3 Working Directory Structure

The directory extracted during section 3.2 contains the following files and folders required for the tool to operate:

● Data: Final feature delineation outputs are saved to this location. The user can delete 

files contained in this directory. Note that storing other files in this directory does not 

cause errors.

● Scratch: Intermediate rasters and shapefiles generated during processing are saved to 

this location. Most of these files are deleted at the end of a processing run, but some are 

left to aid the user in troubleshooting unexpected problems detected in the results. Intermediate results are overwritten during each processing run. The user may delete files 

contained in this directory. However, storing any additional files to this location may 

cause errors to develop in tool outputs.

● Scratch.gdb: Intermediate geodatabase files are saved to this location. The user may 

delete files contained in this geodatabase. However, this should be done through the 

ArcGIS Catalog, not through Windows File Explorer. The user should not store any additional files to this location.

● Tables: All intermediate tabular files are saved to this location. These files remain after 

processing to aid the user in troubleshooting unexpected problems detected in the results. These tables are overwritten during each processing run. The user may delete files 

contained in this directory. The user should not store additional tables in this location.

● Scripts: The Python scripts containing the operating code for the CFDT and Baseline 

Builder Tool are stored in this location. These files should not be moved or modified in 

any way unless the user is attempting to change the tools’ functionality. 

● Toolbox.tbx: This ArcGIS toolbox is the intermediary between the Python script in the 

Scripts folder and the ArcMap interface that allows the user to enter tool run parameters 

and execute processing runs. The toolbox should not be moved or modified.

● Docs: Tool “readme” documents are stored in this location, including this user manual 

and example argument text (.txt) files for executing the CFDT and Baseline Builder 

Tool outside of the ArcMap environment. Original files that are unpacked with the tool 

in this directory should not be deleted as the user may require them for reference. Other 

files may be stored in this directory.

● Inputs: This directory is provided as a location to store DEM and offshore baseline datasets used as initial tool inputs. Use of this folder is optional and users may add, remove, 

or modify files in this folder as desired. 

Except for the “Inputs” folder, the CFDT and Baseline Builder Tools reference the above folders 

by pathname. Modifying the names of any folders causes the tool to fail. Adding other folders to 

the directory is acceptable.
17

4. Input Data Requirements

4. Input Data Requirements

Two datasets are required for the CFDT to run: a raster DEM and an offshore baseline. 

Requirements for the datasets appear in this section.

4.1 The Raster Digital Elevation Model

● The “Raster DEM” is a raster digital elevation model (DEM) in Georeferenced Tagged 

Image File Format (.geotiff) that characterizes the topography on and around the seacliffs (fig. 10). 

● Topobathymetric or topographic DEMs may be used. In either case, data values must 

exist at the seaward and landward extent of cross-shore transects. If there is insufficient 

DEM coverage on transect extents, the user can use ArcMap’s “Euclidean Allocation” 

and “Mosaic to New Raster” tools to extend the DEM with proxy values drawn from the 

DEM’s edge.7

● Any patches of “Null” or “NoData” values within the data extent of the raster DEM 

should be filled; otherwise, cliff features are delineated erroneously. The user can apply 

raster extension techniques, such as ArcMap’s “Euclidean Allocation” and “Mosaic to 

New Raster” tools, to fill these areas. Additionally, if a hydro-flattened DEM is available 

for the study area, the voids are already filled. 

● The CFDT accepts DEMs in any spatial resolution, including those derived from traditional aerial lidar and small unmanned aerial system (sUAS) missions. During CFDT 

testing, 1.0- and 0.5-m resolution DEMs were appropriate to delineate the talus and 

subsidiary cliff features on seacliffs 20–50 m tall—coarser resolutions may be acceptable for larger cliffs, and finer resolution may be beneficial for smaller cliffs. Generally, 

if a DEM’s resolution is too coarse for the user to recognize an existing talus or convexities-concavities on an elevation profile of a cliff face, finer resolutions (if available) can 

improve delineation. 

● It is not advisable to substitute a digital surface model (DSM) for the DEM. A DSM 

includes elevation values representing foliage and built structures. These elements may 

cause cliff feature misclassifications, as the tool cannot distinguish between bare-earth 

elevations and built structures or trees.

● The DEM must be projected in a Universal Transverse Mercator (UTM) coordinate 

system, with the vertical and horizontal units in meters. Additionally, the horizontal and 

vertical coordinate system used must match that of the offshore baseline. Use the “ArcMap Project” tool to change the spatial reference of a DEM or baseline shapefile.8

7For more information on the “Euclidean Allocation” tool, please visit https://desktop.arcgis.

com/en/arcmap/10.6/tools/spatial-analyst-toolbox/euclidean-allocation.htm. For more information on the “Mosaic to New Raster” tool, please visit https://desktop.arcgis.com/en/arcmap/10.6/

tools/data-management-toolbox/mosaic-to-new-raster.htm.

8For more information on the Esri ArcGIS “ArcMap Project” tool, see https://desktop.arcgis.

com/en/arcmap/10.6/tools/data-management-toolbox/project.htm.
18

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Figure 10. Images showing (A) the raster digital elevation model (DEM) with an overlying offshore 

baseline generated with the Baseline Builder Tool, along with cross-shore transects split into landward 

and seaward components, as specified by the distance parameters selected by the user. (B) The transect interval (a 5-meter [m] interval in this example) determines the alongshore resolution of the Cliff 

Feature Delineation Tool (CFDT) outputs.

Landward

transect

component

Seaward

transect

component

Offshore

baseline

Raster DEM

Meters

High : 35

Low : -5

100

Meters

Transect 

interval

5 m

5 m

5 m

5 m

5 m

5 m

A

B
19

4. Input Data Requirements

4.2 The Offshore Baseline

● The Offshore Baseline input is a polyline running alongshore and seaward of the seacliff features to be delineated (fig. 10). Cross-shore transects are generated perpendicular to this baseline, with the longest component cast in the landward direction. 

● For obtaining the best results, this baseline should be approximately 5–30 pixels from 

the seaward extent of the cliff toe or talus debris fan (if one exists). The baseline setback 

should be considered at the same time as the settings for the Landward Distance and

Seaward Distance parameters (section 5.2.4). There is no maximum length limitation 

on the baseline.

● Baseline segments may assume any orientation and direction. However, large changes 

in baseline segments’ angle bearing between adjacent cross-shore transects should be 

minimized. Gaps should be left in the baseline where no cliff features exist, around narrow jutting headlands, and in areas where the analyst does not want tool outputs. 

● The input baseline shapefile may be single or multipart, providing all entries in the attribute table have an “ID” field with the same value.

● The offshore baseline shapefile must be defined in a projected UTM coordinate system, 

and the spatial reference must match that of the input raster DEM.9 To change the spatial reference of a DEM or baseline shapefile, use the ArcMap “Project” tool.10

TIP: The included Baseline Builder Tool can automatically generate an offshore baseline, use 

a baseline from a previous dataset, or allow a new baseline to be digitized manually. Baselines 

generated with the Baseline Builder Tool automatically conform to projection and attribution 

requirements. For more information on automatically generating a baseline, see section 6.

9To check the spatial reference of the input DEM or baseline, right-click on the raster or shapefile 

in the ArcMap Catalog, click “Properties,” select the “General” tab, and scroll down to the “Spatial Reference>>xy” coordinate system entry.

10For more information on the ArcMap “Project” tool, see https://desktop.arcgis.com/en/

arcmap/10.6/tools/data-management-toolbox/project.htm.
20

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

5. Running the Tool

5.1 Initiating a Cliff Feature Delineation Tool Run

Follow the steps in figure 11 to run the Cliff Feature Delineation Tool.

Software steps Visual guidance

1. Open ArcMap, open the Catalog 

pane, and expand the “Folder 

Connections” folder. Expand the 

CFDT directory,11 which may 

take a moment to process.

2. Expand the “Toolbox.tbx” file, 

right-click on the “Cliff Feature 

Delineation Tool,” and select 

“Open” from the dropdown list.

3. Fill out the CFTD dialog box 

with the desired input datasets 

and processing settings. Click the 

“Show Help” button at any time 

for an explanation of settings. 

When all settings are chosen, 

click “OK” to initiate the processing run.

Figure 11. Instructions for initiating a Cliff Feature Delineation Tool (CFDT) run.

11If the “CFTDv1” directory does not appear in the “Folder Connections” folder, follow step 3 of 

section 3.2 in this guide to reestablish the directory in the connected-folders list.
21

5. Running the Tool

5.2 Explanation of Tool Inputs and Starting Parameters

An explanation of tool parameters and tips on how to select input values is below. For 

a more detailed conceptual description on the function of parameters and associated processes, 

please refer to section 2.

5.2.1 Offshore Baseline Parameter

The “Offshore Baseline” input is a reference polyline shapefile from which cross-shore 

transects are cast onto seacliffs. The user can use the browse button to navigate to, and select, a 

baseline shapefile. The dataset must meet the requirements detailed in section 4.2.

5.2.2 Smooth Baseline Parameter

The Smooth Baseline input determines whether or not the algorithm smooths the input 

baseline before processing. Some input baselines, such as those generated by the Baseline Builder Tool, are already smoothed and additional smoothing may not be appropriate. 

● No: Baseline smoothing is not performed. This is the default option.

● Yes: Baseline smoothing is performed. The level of smoothing is determined by the 

Baseline Smoothing Tolerance parameter described below.

5.2.3 Baseline Smoothing Tolerance

The “Baseline Smoothing Tolerance” parameter is optional and specifies the extent of 

smoothing performed on a baseline before processing, assuming the user selected “Yes” for 

the “Smooth Baseline” option described above. The input, which represents meters, can be any 

integer between 0 and 1,000. The relative influence of high (larger input) and low (smaller input) 

smoothing tolerances is displayed in section 6.2.

5.2.4 Raster DEM Parameter

The “Raster DEM” parameter specifies the DEM characterizing the seacliffs to be delineated. The user can use the browse button to navigate to, and select, a DEM .geotiff. The dataset 

must meet the requirements detailed in section 4.1.

5.2.5 Landward Distance and Seaward Distance Parameters

The “Landward Distance” input is the distance in meters that the cross-shore transect is 

projected landward from the offshore baseline (fig. 10), while the “Seaward Distance” input is 

the distance the cross-shore transect is projected seaward from the baseline. Together, the parameters represent the cross-shore transect footprint, which determines where feature delineation occurs and influences the angle of the chord line generated on each transect. Delineation can suffer 

when the chord line slope is more gradual than the foreshore slope (fig. 4), if the seaward extent 

of the transect falls on, or landward of, the true cliff toe or talus (section 2.4), or if the landward 

transect extent does not reach far enough landward of the cliff toe. 

The landward transect distance can often be 95 percent of the total transect length. In 

most situations, the seaward distance may be kept short (1 m) but can also be extended to prevent 

the seaward end of the transect from falling on top of the cliff toe’s true location when baselines 
22

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

intersect with the cliff face or true toe. (section 2.4). The seaward and landward distances should 

never extend cross-shore transects into areas of a DEM with null values, as this introduces error 

into feature delineation results. It is important to remember that if there is insufficient DEM coverage seaward of the baseline, the user can use ArcMap’s “Euclidean Allocation” and “Mosaic to 

New Raster” tools to extend the DEM with proxy values drawn from the DEM’s edge.12

TIP: A useful strategy for processing in this version of the CFDT is to generate cross-shore transects 

with a seaward extent that is set back from the seaward extent of the cliff face by a distance approximate to the specified spatial kernel size in meters. In this scenario, the refined delineation methods 

are likely to classify the cliff toe accurately, even when the basic toe is erroneous. The Baseline 

Builder Tool can be set up to build a baseline close to the cliff face, and the seaward transect distance 

can add seaward extent as needed. The “Landward Transect Distance” input should be set so that the 

true cliff top is easily encompassed by the cross-shore transect. In delineation tests on cliff features 

20–50 m tall and without complex high-relief features landward of the cliff face, cliff toe and top 

delineation were still successful when the landward transect extent overshot the true cliff top by 

40 m or more. There is little consequence, other than additional processing time, when the landward 

transect extent overshoots the true cliff top; if it falls short, the feature is erroneously classified.

5.2.6 Transect Interval Parameter

The “Transect Interval” input is the distance, in meters, along the offshore baseline between generated transects (fig. 10). This input determines the alongshore resolution of cliff feature outputs. A higher transect frequency (1–5 m or less) can be chosen when input DEMs have 

high resolution, cliffs are not very high relief, and study areas are small (1-km shoreline length 

or less) where fine scale linear outputs are meaningful. For larger regional analysis, alongshore 

transect frequency can be lower (5–50 m or more) to improve processing time. Increasing the 

frequency of transect generation increases processing time. 

5.2.7 Delineation Mode Parameter

The Delineation Mode input determines which algorithms are used to identify final cliff 

features. The different mode options are described below:

● Basic Delineation: This setting outputs cliff tops, midpoints, and toes associated only 

with “Basic Delineation” (see section 2.3 for more information on how “Basic Delineation” works).

● Refined Delineation: This setting outputs cliff tops and midpoints as with “Basic Delineation,” but cliff toes are derived from a chosen refined delineation method. The Refinement Method (either high pass or first concavity) is specified by the “Refinement 

Method” parameter below.

● Multi Delineation: This setting outputs cliff tops, midpoints, as well as all possible versions of refined toes. Outputs include a basic cliff toe, a cliff toe refined with the HighPass method, and a cliff toe refined with the First Concavity method.

12For more information on the Esri ArcGIS “Euclidean Allocation” tool, visit https://desktop.

arcgis.com/en/arcmap/10.6/tools/spatial-analyst-toolbox/euclidean-allocation.htm. For more 

information on the Esri ArcGIS “Mosaic to New Raster” tool, visit https://desktop.arcgis.com/en/

arcmap/10.6/tools/data-management-toolbox/mosaic-to-new-raster.htm.
23

5. Running the Tool

TIP: “Basic Delineation” mode performs especially well on high-relief or sheer cliffs where 

cross-shore transects can be kept relatively short. Refined delineation methods perform comparatively well when the cliff morphology is complex and cross-shore transects must be extended.

5.2.8 Refinement Method Parameter

If “Refined Delineation” mode is selected in the previous step, there are two methods 

available for toe-position refinement:

● High Pass: This method identifies the cliff toe by analyzing a high-pass profile derived 

from the slope of the raster DEM underlying the cross-shore transects (see section 2.4 for 

more information on the “High Pass” method). This method of toe refinement is more 

likely to identify the toe at the seaward edge of a talus. Cliff tops and midlines are identified using the same method as “Basic Delineation” mode 

● First Concavity: This method identifies the cliff toe by projecting a chord line between 

the coarsely delineated toe and the cliff midline, and then runs a one-dimensional slopeanalysis kernel across the elevation profile surface between the toe and midline (see 

section 2.4 for more information on how the first concavity method works). The size of 

the analysis kernel is determined by the Kernel Size input parameter further detailed in 

section 5.2.11.

TIP: “Multi Delineation” mode (section 5.2.7) generates high pass, first concavity, and basic 

toes. If the user is unsure which refinement method might yield the best results, “Multi Delineation” mode is an effective choice that negates the input for the “Refinement Method.”

5.2.9 High Pass Threshold Parameter

The High Pass Threshold input controls the high-pass-filtered threshold used to refine 

the location of the cliff toe for the “High Pass” refined delineation method. A point along a transect with a greater negative value (further from zero) than the threshold triggers toe identification. If no value is triggered by the user-defined threshold on the lower half of the cliff, the value 

is automatically revised closer to zero until a threshold is triggered (see section 2.4 for more 

information on how the “High Pass” method works).

The default value of –25 may not be optimal for all cliff morphologies, but it is an effective starting point. First running CFDT with the default value of −25 and evaluating the delineated features in a 3D format is recommended, as high-pass values interpreted without context 

could appear arbitrary. If the cliff toe is consistently delineated landward of the true toe location, 

consider using a value closer to zero. If the delineated location is consistently seaward of the true 

toe location, consider a value further from zero. The allowed input range is from −6 to −50.

TIP: If the user chooses “First Concavity” for the “Refinement Method” parameter, this input is 

negated.

5.2.10 Subsidiary Feature Delineation Parameter

The Subsidiary Feature Delineation input determines whether subsidiary features are 

delineated as 3D point shapefiles. Subsidiary features are convexities and concavities on the cliff 

face and can represent geologic controls on cliff morphology (see section 2.5 for more information on how “Subsidiary Feature Delineation” works).
24

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

● Yes: Subsidiary features are delineated; this is the default setting. The algorithm allows 

one convexity and one concavity to be delineated on the lower and upper halves of the 

cliff, permitting a maximum of four points per cross-shore transect.

● No: Subsidiary features are NOT delineated.

Like “First Concavity” toe refinement, “Subsidiary Feature Delineation” uses a one-dimensional slope-analysis kernel, and the size of the one-dimensional kernel used in this process 

is enforced by the “Kernel Size” parameter in section 5.2.11.

5.2.11 Kernel Size Parameter

The “Kernel Size” input modifies the size of the one-dimensional analysis kernel used 

in “First Concavity” toe refinement and “Subsidiary Feature Delineation.” The kernel size is the 

number of cells in a processing kernel (the kernel’s neighborhood) and the default input is three 

cells (resulting in a 1x3 cell neighborhood running along the cross-shore transect). Because a 

kernel must have a central member, the kernel size must be an odd value and can never be less 

than three cells in size. Users are encouraged to check the spatial resolution of their input DEM 

when choosing a kernel size so that they are aware of the planar length of the kernel in meters. 

During tool development, subsidiary delineation was tested on a 1-m resolution DEM with 

kernel sizes of three and five cells (3-m and 5-m spatial kernels). Both kernel sizes yielded acceptable concavity locations on cliffs 30–40 m in height. If higher resolution DEMs are used as inputs, 

users should consider increasing the kernel size to maintain a relevant spatial kernel length. For 

instance, for a DEM with a cell resolution of 0.5 m, a kernel size of seven would result in a 3.5-m 

spatial kernel. Significantly smaller cliffs benefit from a smaller spatial kernel, and taller or gradually sloping cliffs benefit from a larger spatial kernel. When all other conditions are equal, a larger 

spatial kernel is less sensitive to deviations in surface slope over small distances.

5.2.12 Output Smoothing Tolerance Parameter

The Output Smoothing Tolerance input (in meters) determines the level of smoothing 

performed on cliff feature line outputs. The higher the tolerance, the more smoothing is performed. A lower tolerance results in fewer modifications to output line features while leaving the 

feature with more angular transitions between segments.

5.2.13 Output Cleanup Parameter

The Output Cleanup input determines how to handle feature-line cutbacks or regions 

where more than one instance is identified along a single cross-section profile. Cutbacks can 

occur along crenulated sections of coast and narrow headlands where offshore baselines have 

excessive curvature (fig. 12). Cutbacks can also be identified in areas where cross-shore transects 

overlap with both sides of a jutting headland. Cutbacks can be handled in two ways:

● Flag Cutbacks: This is the default setting. The tool flags cross-shore transects with 

cutbacks along their extent, saving them for use in data review and modification by the 

user. This setting is also useful in situations where the user does not want to automatically delete the outputs around narrow, jutting headlands.

● Delete Cutbacks: The tool automatically deletes sections of the cliff feature lines 

around cross-shore transects on which cutbacks were detected.
25

5. Running the Tool

5.2.14 Series Name Parameter

The Series Name input adds a user-specified suffix to the names of final model outputs. Final outputs are written to the “Data” folder within the workspace. The closed phrase “SeriesName” 

in the following shapefile output conventions is merely a placeholder for the name a user assigns 

when generating final model output files. The naming conventions for outputs are as follows:

● Cliff top polyline shapefile: CliffTopLine3D_SeriesName.shp

● Cliff midline polyline shapefile: Midline3D_SeriesName.shp

● Basic cliff toe polyline shapefile: CliffToeLine3D_SeriesName.shp

● Cross-shore transects polyline shapefile: Transects3D_SeriesName.shp

● Refined toe polyline shapefile (High Pass): RefinedToeHPLine3D_SeriesName.shp

● Refined toe polyline shapefile (First Concavity): RefinedToeFCLine3D_SeriesName.shp 

● Subsidiary features point shapefile: SubsidiaryFeatures3D_SeriesName.shp 

● Basic toe, refined toes, midpoints, and tops point shapefile: PrimaryFeaturePoints_

SeriesName.shp

● Flagged cutback transects: CutbackTransects_SeriesName.shp

Figure 12. An image showing the cliff top line, cross-shore transects, and flagged cutback transects. Cutback transects mark any locations where cliff feature lines, such as the cliff top, cut back 

on themselves alongshore. In this example, feature line cutbacks occurred because the baseline 

exhibited too much curvature around a jutting headland. DEM, digital elevation model.

Cliff top

Baseline

Flagged

cutback

transects

Cross-shore

transects

Raster DEM

Meters

High: 35

Low: -5 50

Meters
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Additionally, an error-log table is generated in the “Tables” folder within the workspace 

following the naming convention TransectErrorRecord_SeriesName.csv. If there are unexpected 

gaps in the delineated outputs, they may be explained in this table. 

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

6.1 Baseline Builder Tool Overview

As mentioned in section 5.2.1, offshore baselines should be digitized close to the cliff 

features delineated (approximately 5–30 pixels seaward of the cliff face). By using refined delineation methods, baselines can be farther from the cliff and still produce clear feature delineations. However, initiating cross-shore transects farther from the cliff increases the probability that 

adjacent cross-shore transect lines cross over one another before reaching the cliff face, generating cliff feature cutbacks during delineation. Consistent baseline placement is also useful when 

digital surface models from photogrammetric approaches are used as “Raster DEM” inputs into 

the CFDT, as these datasets rarely extend seaward of the subaerial beach and cannot accommodate cross-shore transects cast from offshore where no data exist.

Maintaining a consistent distance from the cliff face and line curvature when manually 

vectorizing the offshore baseline from a DEM or aerial image can be difficult. To this end, a 

Baseline Builder Tool is included in the working directory toolbox that can generate an automated baseline around cliff features in a study area. Users can treat this baseline as the “Offshore 

Baseline” input into CFDT or use it as a manual vectorization guide, helping users vectorize their 

baseline at consistent distances from cliff features. 

The Baseline Builder Tool operates by scanning the DEM and selecting areas where high 

relief features meet the topographic relief threshold specified by the user. First, an analysis kernel 

calculates the elevation range in a neighborhood around each pixel of the DEM, with the results 

output to a new raster (figs. 13A, B). Cells that meet or exceed an elevation-range threshold 

specified by the user are then classified as relief regions (fig. 13C). Both the size of the kernel 

neighborhood and the elevation-range threshold are modifiable, allowing the user to direct the algorithm to only classify certain cliff morphologies. For instance, by specifying a relatively small 

kernel neighborhood and a relatively large elevation-range threshold, only tall, high-relief cliffs 

classify as relief regions. The classified area is then buffered by the distance the user chooses the 

offshore baseline to be from the cliff face (fig. 13D). 

The above topographic analysis scans the entire input DEM for relief regions, and buffers are produced both landward and seaward of classified pixels (fig. 13D). Segments are filtered 

by their maximum elevation to remove buffer segments occurring on the landward side of cliffs 

(fig. 13E). Specifically, the filter removes buffer segments with a maximum elevation above the 

mean elevation of the classified relief area, minus 1 standard deviation. Finally, the remaining 

buffer is smoothed with a tolerance specified by the user (fig. 13F). This process leaves smoothed 

polylines offset a consistent distance seaward of classified relief features. The user then enters a 

short editing session where the smoothed line is quality-reviewed for use as an offshore baseline 

input or used as a vectorization guide for a manually digitized baseline.
27

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

Figure 13. Images showing (A) the ”Raster DEM” input into the Baseline Builder Tool; (B) the elevation 

range around each pixel within the neighborhood of the analysis kernel; (C) a classified relief region satisfying the user’s elevation range specifications; (D) a polygon buffer projected outwards around the classified 

relief region; (E) the buffer remaining after being elevation-filtered to remove any landward components; 

and (F) the final, smoothed offshore baseline. DEM, digital elevation model; NAVD 88, North American 

Vertical Datum of 1988.

Raster DEM

Meters, NAVD88

High: 35

Low: -5

100

Meters

Elevation range

Meters

High: 30

Low: 0

Relief region

Relief buffer Elevation-filtered buffer Smoothed baseline

A B C

D E F
28

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

6.2 Running the Baseline Builder Tool

Follow the steps in figure 14 to operate the Baseline Builder Tool.

Software steps Visual guidance

1. Open ArcMap and expand 

“Toolbox.tbx” in the CFDT 

working directory, right-click 

on the “Baseline Builder” 

script, and select “Open” in 

the dropdown list. 

2. Select the desired options 

in the tool dialog box. Once 

all settings are chosen, click 

“OK” to initiate the processing run.

•	 Parameters and inputs introduced in this dialog box 

are described in detail in 

section 6.3.

•	 Click the “Show Help” 

button anytime to show an 

explanation of input parameters.

Figure 14. Instructions for running the Baseline Builder Tool. CFDT, Cliff Feature Delineation Tool; DEM, 

digital elevation model.
29

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

Software steps Visual guidance

3. Once the run has completed 

successfully, expand the 

“Data” folder, and add the 

tool output “AutoBase_Output 

Name.shp” to the map. The 

shapefile should appear as a 

polyline running alongshore 

and seaward of cliff features. 

Adding the DEM to the map 

for reference is also helpful.

Figure 14. Instructions for running the Baseline Builder Tool. CFDT, Cliff Feature Delineation Tool; 

DEM, digital elevation model.—Continued

TIP: Like the CFDT, the Baseline Builder Tool generates intermediate outputs in the 

“Scratch” folder, which are overwritten during each processing run. One output in particular, 

“CliffRegion.tif,” shows the raster areas the Baseline Builder Tool classified as meeting the 

user’s “Cliff Height” and “Neighborhood” settings. If unsatisfactory gaps are seen in the baseline 

output in step 3, they should correspond to gaps in this intermediate output where relief was too 

low to satisfy the input parameters. The user can then rerun the Baseline Builder Tool with more 

appropriate “Cliff Height” and “Neighborhood” settings or digitize that section manually.

6.3 Explanation of Baseline Builder Tool Starting Parameters

Explanations of the Baseline Builder Tool inputs and starting parameters introduced in 

figure 14, step 2, are given in this section. 

6.3.1 Input DEM Description

The Input DEM is the DEM containing the cliff features from which the baseline should 

be built seaward. This is the same “Raster DEM” that is used for cliff feature delineation.
30

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

6.3.2 Cliff Height Setting

The Cliff Height is the minimum height of cliffs, in meters, the user desires to delineate 

in the study area. Selecting a greater height prevents a baseline from being built offshore from 

lower cliffs. This height should be interpreted as the vertical distance between the beach or cliff 

toe and the top of the cliff.

6.3.3 Neighborhood Setting

The Neighborhood is the 2D kernel size, in meters, used to scan the DEM for the userspecified “Cliff Height.” If the elevation range over the areas of the kernel meets or exceeds the 

parameter for “Cliff Height,” the central kernel member is classified as cliff area, and a baseline 

can be built seaward of it. 

6.3.4 Baseline Distance Input

The Baseline Distance is the chosen seaward distance, in meters, between the cliff face and 

the offshore baseline. It determines how close the baseline or digitizing guide is built from the cliff.

6.3.5 Smoothing Tolerance Input

The Smoothing Tolerance input controls how smooth the curvature is on output baselines. For this application, a minimum “Smoothing Tolerance” of 100–150 m is necessary to 

remove sharp bends in the baseline. The higher the “Smoothing Tolerance,” the more gradual the 

curvature in the output baseline (fig. 15).

6.3.6 Filter Type Parameter

The Baseline Builder Tool constructs polylines on both landward and seaward sides of 

relief features and uses elevation filtering to extract only the polylines seaward of relief features. 

Two modes of elevation filtering for the Filter Type input can be used: “Automatic” and “Manual Threshold.”

● Automatic: The “Automatic” setting works well when the input raster DEM does 

not extend far inland or when most relief features detected by the “Cliff Height” and 

“Neighborhood” parameters are associated with the seacliffs. This input requires no additional input from the user. The performance under this setting degrades when rasters 

extend further inland and more relief features are classified at higher elevations.

● Manual Threshold: The “Manual Threshold” setting works well when the raster DEM 

extends far inland or when many relief features are classified away from the shoreline at 

higher elevations. When enabled, the algorithm extracts polylines falling within a userspecified elevation range (see the “Maximum” and “Minimum Elevation Threshold” 

parameters below).

6.3.7 Maximum Elevation Threshold Setting

Polylines occurring above the Maximum Elevation Threshold elevation are filtered out 

of baseline results under the “Manual Threshold” filter-type setting; this setting is unavailable 

under the “Automatic” filter-type setting.
31

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

6.3.8 Minimum Elevation Threshold Setting

Polylines occurring below the Minimum Elevation Threshold elevation are filtered out 

of baseline results under the “Manual Threshold” filter-type setting; this setting is unavailable 

under the “Automatic” filter-type setting.

6.3.9 Output Name

The Output Name is the suffix of the name given to the output digitization guide or automatic baseline: AutoBase_OutputName.shp.

TIP: The “Cliff Height” and “Neighborhood” parameters can be interpreted as scanning for 

levels of topographic relief and slope. Thus, the user can specify heights and kernel areas that are 

associated with features much shorter than cliffs and that occur over shorter planar distances. 

Figure 15. An image showing offshore baselines generated with different smoothing tolerances 

(1,000 meters [m], 600 m, 300 m, and 100 m) using the Baseline Builder Tool. Cross-shore transects are 

projected perpendicular to a given baseline segment, so the smoothing tolerance increases or decreases 

the local variability in the bearing of the transects cast. If aggressive smoothing brings the baseline in contact with cliff features, the baseline is automatically clipped. DEM, digital elevation model; NAVD 88, North 

American Vertical Datum of 1988.

Smoothing

tolerance 1000

meters

Smoothing

tolerance 600

meters

Smoothing

tolerance 300

meters

Smoothing

tolerance 100

meters

Raster DEM

Meters, NAVD88

High: 35

Low: -5

210

Meters

1,000

Meters
32

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

6.4 Reviewing Baseline Builder Tool Outputs

Follow the steps in figure 16 to edit the Baseline Builder Tool output for use as an offshore baseline.

Editing steps Visual guidance

1. Add the “Editor” toolbar to 

the map by clicking “Customize” in the menu at the top of 

the ArcMap window, selecting 

“Toolbars,” from the dropdown list, and then selecting 

“Editor” from the subsequent 

dropdown list.

2. After adding the baseline 

and DEM to the map, start an 

editing session by clicking the 

“Editor” dropdown list on the 

toolbar and selecting “Start 

Editing” on the dropdown list. 

Copying and saving a version 

of the data to be edited before 

an editing session is a suggested practice; edits saved during 

an editing session cannot be 

undone.

Figure 16. Instructions for editing the Baseline Builder Tool output for use as an offshore baseline.
33

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

Editing steps Visual guidance

3. Ensure that baseline sections 

were not produced in inappropriate areas. For instance, 

baselines may be produced 

around high-relief bathymetry or running cross-shore 

adjacent to canyons or gullies 

close to the shoreline. There 

may also be curved line sections at the end of baselines 

where cliff features within 

the parameters specified by 

the “Cliff Height” setting no 

longer exist.

4. If inappropriate sections are 

found, click the “Edit” icon on 

the “Editor” toolbar, which lets 

a user select features on the 

map. Delete unwanted sections 

by selecting them—multiple 

features can be selected by 

holding the left mouse button 

and dragging a bounding box 

around the desired features 

or by holding the shift key 

while left-clicking individual 

features—and pressing the 

delete key.

Figure 16. Instructions for editing the Baseline Builder Tool output for use as an offshore 

baseline.—Continued
34

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Editing steps Visual guidance

5. Gaps in the baseline, around 

specific features, can be created by selecting a line with the 

“Edit” icon and then selecting 

the “Split Line” icon from the 

toolbar. Click on the two extents of the line (start and end) 

where the gap is needed.

6. Once the gap sections are split 

from the baseline, select the 

sections to be removed with 

the “Edit” icon, and delete 

them by pressing the “Delete” 

key.

Figure 16. Instructions for editing the Baseline Builder Tool output for use as an offshore 

baseline.—Continued
35

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

Editing steps Visual guidance

7. Remove unwanted curved sections at the end of baselines by 

repeating steps 5 and 6. Note 

that these end sections only 

need to be split at one point, 

not two.

8. Automatic baseline sections 

can be manually redigitized as 

needed. The simplest method 

is to select the section to be 

edited and then select the 

“Reshape Feature” icon on the 

“Editor” toolbar. Now, click 

on the starting extent of the 

baseline section where manual 

digitization is needed. Vertices 

can then be added alongshore 

where desired.

Figure 16. Instructions for editing the Baseline Builder Tool output for use as an offshore 

baseline.—Continued
36

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Editing steps Visual guidance

9. The final vertex must end on 

the automatically generated 

baseline, representing the end 

extent of the section to be 

reshaped. Right-click and select “Finish Sketch” from the 

dropdown list that appears.

10. Once all changes are made, 

expand the “Editor” dropdown 

list and click “Save Edits.” 

Next, click “Stop Editing.” 

The baseline can now be used 

as an input to the CFDT.

Figure 16. Instructions for editing the Baseline Builder Tool output for use as an offshore baseline.—Continued

TIP: Steps 4–7 require that the “Snapping” setting be enabled, and an appropriate snapping 

tolerance can make baseline editing easier. To enable or modify the snapping tolerance, open the 

“Editor” toolbar dropdown list, navigate to “Snapping,” click “Options,” and set the “Tolerance.” 

A higher number causes the mouse cursor to snap to the baseline from farther away, and a tolerance of 0 disables snapping.
37

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

6.5 Manually Digitizing an Offshore Baseline

Follow the steps in figure 17 to manually digitize a baseline using the Baseline Builder 

Tool output as a guide. 

Digitizing steps Visual guidance

1. Create an empty polyline feature 

class by opening the ArcMap 

“Search” tab near the top of the 

ArcMap window. Type in “Create Feature Class” in the search 

window and open the “Create 

Feature Class” tool.

2. Run the “Create Feature Class” 

tool. Type in a name for the manual baseline and choose a folder 

into which it can be output. Select “Polyline” for geometry type 

and specify a coordinate system 

(which must be the same spatial 

reference as the DEM). All other 

dialog options can be left with 

default values or blank. Click 

“OK.” This process generates an 

empty polyline shapefile at the 

directory location specified and 

adds it to the map.

Figure 17. Instructions for manually digitizing a baseline, with the Baseline Builder Tool output used as 

a digitizing guide. CFDT, Cliff Feature Delineation Tool; DEM, digital elevation model.
38

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Digitizing steps Visual guidance

3. If not already done, add the 

“Editor” toolbar to the map by 

clicking the “Customize” menu 

at the top of the ArcMap window, 

selecting “Toolbars,” and then 

selecting “Editor.”

4. Start an editing session by clicking the “Editor” dropdown list on 

the toolbar and selecting “Start 

Editing.”

5. Open the “Create Feature” tab on 

the “Editor” toolbar. Select the 

empty shapefile generated during 

step 2 from the layers displayed 

on the “Create Feature” tab, then 

select the “Line” option from the 

“Construction Tools” at the bottom of the “Create Features” tab.

Figure 17. Instructions for manually digitizing a baseline, with the Baseline Builder Tool output used as 

a digitizing guide. CFDT, Cliff Feature Delineation Tool; DEM, digital elevation model.—Continued
39

6. Using the Baseline Builder Tool and Vectorizing an Offshore Baseline

Digitizing steps Visual guidance

6. Click on the map to manually 

add baseline vertices.

7. If needed, hovering the mouse 

cursor near an automated baseline added to the map snaps the 

mouse cursor onto it. The snapping tolerance can be changed 

(making it easier or harder for 

the cursor to snap to the baseline 

extent) by opening the “Editor” 

toolbar dropdown list, navigating 

to “Snapping,” selecting “Options,” and changing the “Tolerance.” A higher number causes 

the input-device cursor to snap to 

the baseline from farther away, 

and a tolerance of zero disables 

snapping.

Figure 17. Instructions for manually digitizing a baseline, with the Baseline Builder Tool output used as 

a digitizing guide. CFDT, Cliff Feature Delineation Tool; DEM, digital elevation model.—Continued
40

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Digitizing steps Visual guidance

8. Finish a baseline section at any 

time by right-clicking on the map 

and selecting “Finish Sketch.” 

Alternatively, cancel a baseline 

segment by right-clicking and 

selecting “Delete Sketch.” Subsequent sections can be added by 

following steps 6–7 and clicking 

“Finish Sketch” at the end of 

each segment.

10. Once all segments are digitized, 

expand the “Editor” menu and 

click “Save Edits.” Then click 

“Stop Editing” to end the editing 

session. The baseline is now 

ready to be used in the CFDT.

7. Visualizing and Reviewing Cliff Feature Delineation Tool Outputs

Several visualization and review options are available for CFDT outputs. Features can be 

projected in a 3D format in ArcScene, which provides the most rapid means of assessing the validity of tool outputs and is the preferred format for manually editing cliff feature lines. Data products 

Figure 17. Instructions for manually digitizing a baseline, with the Baseline Builder Tool output used as a 

digitizing guide. CFDT, Cliff Feature Delineation Tool; DEM, digital elevation model.—Continued
41

7. Visualizing and Reviewing Cliff Feature Delineation Tool Outputs

can also be displayed in a 2D format in ArcMap where cross-shore elevation profile graphs can be 

generated from transects. Both ArcScene and ArcMap give access to output shapefile attribute tables 

which provide coordinate information on the location of delineated features on cross-shore transects. 

7.1 Visualizing Features in ArcScene

To open the CFDT outputs in a 3D environment, first open ArcScene, which should be 

included in the ArcGIS installation. Next, open the “Catalog” and, if necessary, connect to the 

CFDT working directory before expanding the “Data” folder, as described in section 3.2. Add 

any of the desired cliff feature outputs to the map by dragging the shapefiles from the catalog 

into the main map panel. A list of the possible outputs can be found in section 5.2.14. 

To change the symbology for output shapefiles, navigate to the “Table of Contents” and 

double click on the current symbology for a given shapefile, which opens the “Symbol Selector”

(fig. 18). Change the line or point color or width and click “OK” when finished.

Several navigation tools are available at the top of the ArcScene window to allow the user 

to explore the 3D scene. Ensure that the navigation tools are visible by opening the “Customize” 

menu, expanding “Toolbars,” and ensuring “Tools” is checked. Use “Navigate Mode” to change the 

view of outputs in the map panel (fig. 19). Holding the left mouse button while moving the mouse 

rotates the current view. Scrolling the center mouse wheel zooms in and out of the current view. 

The scene can be panned by using “Pan Mode” (fig. 19) or pressing down the central mouse wheel 

while dragging the mouse. The level of zooming and panning permitted by ArcScene depends on 

how far the current view is panned from a “Camera Target,” which is not overtly displayed to the 

user. If panning or zooming becomes restricted, set a new camera target on a feature in the center 

of the screen by clicking a desired feature with the “Center on Target” button (fig. 19) or by holding 

down the “Ctrl” key and left-clicking on a feature while in “Navigate Mode.” Returning to a full 

view of all features in the map is accomplished by clicking on the “Full Extent” icon (fig. 19).

Figure 18. An image showing the ArcScene “Table of Contents” and “Symbol 

Selector,” which can be used to change the symbology of output shapefiles.
42

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Figure 20. Instructions for editing any cliff feature line in ArcScene.

Figure 19. An image showing the key navigation tools (bracketed in red) for 

modifying the camera view in ArcScene, along with selected cliff feature outputs.

7.2 Modifying Features in ArcScene

The process for editing 3D features is like the process for digitizing offshore baselines 

outlined in section 5.2.1. Complete the steps in figure 20 to modify any cliff feature line.

Editing steps Visual guidance

1. If the “3D Editor” toolbar is 

not already added, select the 

“Customize” tab in the main 

menu, select “Toolbars” in 

the dropdown list, and select 

“3D Editor.” 

2. Select the “3D Editor” 

dropdown list and click 

“Start Editing.” Remember 

to create a backup version of 

the shapefile, as saved edits 

cannot be undone.
43

7. Visualizing and Reviewing Cliff Feature Delineation Tool Outputs

Editing steps Visual guidance

3. Select the “3D Editor” 

dropdown list again, select 

“Snapping,” and select the 

“Snapping Window” (“Snapping Environment” checkbox) panel. Additionally, 

check the snapping settings 

under “Options” to ensure 

that a desirable snapping 

tolerance is set. A higher 

tolerance snaps the cursor 

to boundaries from farther 

away.

4. By checking and unchecking boxes in the “Snapping 

Environment” checkbox, 

the user can filter layers and 

choose which parts of the 

lines (“Vertex”, “Edge,” or 

“End”) are allowed for snapping.

5. Removing an erroneous section of cliff feature line first 

requires a user to select the 

line with the “Edit Placement” tool.

Figure 20. Instructions for editing any cliff feature line in ArcScene.—Continued
44

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Editing steps Visual guidance

6. Once selected, use the “Split 

Line” tool to split the erroneous section off at either end 

of its extent. 

Note that the options in the 

“Snapping Environment” 

checkbox window must be 

set to the vertices of the feature being edited in this step.

7. The erroneous section can 

be selected separately with 

the “Edit Placement” tool 

and deleted with the “Delete” key.

8. Redigitizing the erased line 

section is done by opening 

the “Create Features” panel 

on the “3D Editor” toolbar 

and selecting the line to 

be redigitized. Also, select 

“Line” under the “Construction Tools” section of the 

“Create Features” panel.

Figure 20. Instructions for editing any cliff feature line in ArcScene.—Continued
45

7. Visualizing and Reviewing Cliff Feature Delineation Tool Outputs

Editing steps Visual guidance

9. Vertices can now be added 

by snapping to other features 

such as cross-shore transects, 

refined toes, or subsidiary 

feature points. Vertices 

should always be located 

by snapping to existing 

features; otherwise, appropriate height values are 

difficult to determine. When 

satisfied with a segment, 

right-click and select “Finish 

Sketch” from the dropdown 

list. Cancel the segment by 

right-clicking and selecting 

“Delete Sketch” from the 

dropdown list.

10. Complete steps 5–9 to 

edit any other line sections. 

When satisfied with the edits, click on the “3D Editor” 

dropdown list, select “Save 

Edits,” and then select “Stop 

Editing.”

TIP: Quickly switch between the “Create Features” and “Snapping Environments” panels 

by dragging each panel to a different location in the ArcScene window to display both 

simultaneously.

7.3 Visualizing Features in ArcMap

Cliff feature outputs can be added to ArcMap by dragging them from the catalog to the 

main map panel in the same manner as is done in section 7.1, although it is not recommended to 

conduct edits in this format because the view is 2D, and the position of delineated features on the 

cliff face appears ambiguous. During a data review, ArcMap is suitable for generating traditional 

elevation profile graphs and reviewing any cutback transects generated during processing.

Figure 20. Instructions for editing any cliff feature line in ArcScene.—Continued
46

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Complete the steps shown in figure 21 to generate elevation profile graphs and feature 

point locations across a given cross-shore transect in ArcMap.

Software steps Visual guidance

1. Select the “Customize” 

dropdown list at the top of 

the ArcMap window, select 

the “Toolbars” dropdown list, 

and then select “3D Analyst.” 

Add the “3D Transects” to the 

map, along with any other 3D 

features to be mapped, such 

as primary feature points or 

subsidiary features.

2. Select a cross-shore transect 

by clicking on the “Select 

Features” icon located near the 

top of the ArcMap window in 

the main toolbar. 

3. Click the “Profile Graph” icon 

on the “3D Analyst” toolbar, 

which presents an elevation 

profile graph.

Figure 21. Instructions for graphing cross-shore transects and cliff feature points using ArcGIS Desktop.
47

7. Visualizing and Reviewing Cliff Feature Delineation Tool Outputs

Software steps Visual guidance

4. Add primary features (such 

as cliff toes, midpoints, and 

tops) or subsidiary features to 

the graph by selecting them on 

the main map panel. Note that 

the transect itself should be 

deselected for this step; also, 

be sure to only select points 

from the cross-shore transect 

currently being graphed.

5. Move back to the profile graph 

and right-click anywhere on 

the graph, then select “Properties.” Open the “Series” tab, 

click “Add” (at the bottom left 

of the “Graph Properties” dialog box), and then select “New 

Series.”

Figure 21. Instructions for graphing cross-shore transects and cliff feature points using ArcGIS 

Desktop.—Continued
48

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Software steps Visual guidance

6. Populate the series settings. 

For the “Graph Type” field, 

select “Scatter Plot,” and for 

the “Layer/Table” field, select 

the shapefile encompassing 

the features selected in step 

4. For the “Y Field,” select 

“Point_Z,” and for the “X 

Field,” select “DIST” and then 

click “Apply.” 

Note: Points from other transects 

may appear on the graph until 

step 7 is completed.

7. Open the “Appearance” tab 

and select the “Show only 

selected features/records on the 

graph” button. Otherwise, the 

graph displays feature points 

from the whole map. Click on 

“OK.”

Note: Points from other transects 

might be displayed on the 

graph until this step is completed.

Figure 21. Instructions for graphing cross-shore transects and cliff feature points using ArcGIS 

Desktop.—Continued
49

7. Visualizing and Reviewing Cliff Feature Delineation Tool Outputs

Software steps Visual guidance

8. The feature points appear on 

the elevation profile. Rightclicking on a point or part of an 

elevation profile and selecting 

“Identify” displays the elevation (Point_Z) and distance 

(DIST) along the cross-shore 

transect at that location, as well 

as the type of point (“F_Type,” 

primary features only). For 

instance, “ToeFC” indicates 

a toe identified with the first 

concavity method, while “Toe” 

refers to the basic method.

TIP: Change the title and axis labels by navigating to the “Appearance” tab of the graph properties. The elevation profile or point colors can be changed under the “Series” tab. The axis 

scale and other settings can be changed by right-clicking on the graph and selecting “Advanced 

Properties.”

The “3D Transects” shapefile contains additional information in its attribute table, which 

can be accessed by right-clicking on its entry in the “Table of Contents” and selecting “Open 

Attribute Table.” Up to five columns (Top_X, Mid_X, Toe_X, ToeHP_X, and ToeFC_X) record 

the distance along the cross-shore transect where the cliff top, midpoint, basic toe, high-pass toe, 

and first concavity toe were identified, respectively. The “Shape_Leng” column records the total 

cross-shore transect length in meters. Two columns, “Start_Elev” and “End_Elev”, record the 

elevations at the start and end of the transect and can be used to calculate the slope of the chord 

line. The “FMF” column serves two purposes as the unique identifier for the transect and for recording the distance along the offshore baseline at which it was generated. The “FMF” value can 

be referenced in the “SubsidiaryFeatures3D” and “PrimaryFeaturePoints” attribute table under 

the “RIF” column, and it also appears in the attribute tables of many intermediate outputs. Users 

can thereby link the data in any given output to a given cross-shore transect. Both subsidiary and 

primary feature point shapefiles have “Point_Z” and “DIST” fields, which record the elevation 

and distance of the point along a given cross-shore transect. 

7.4 Exporting Features to Text Tables

For point shapefiles such as “PrimaryFeaturePoints” and “SubsidiaryFeatures3D,” there 

are several methods of exporting the results as text tables for use in other software programs. If 

the user has ArcMap’s spatial statistics license enabled, the best method is to select the desired 

Figure 21. Instructions for graphing cross-shore transects and cliff feature points using ArcGIS 

Desktop.—Continued
50

Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

point shapefile as an input into the “Export Feature Attribute to ASCII” tool, which exports the xy

coordinates of each point, along with all attribute-table information. If the user lacks the spatial 

statistics license, they can instead run the “Feature Class Z to ASCII” tool, which exports the xyz

coordinates of each point feature but omits other attribute-table information. Alternatively, the user 

can input the desired point shapefile into the “Add XY Coordinates” tool, which appends xy coordinates to the points’ attribute table entries and then exports the table as a Microsoft Excel file using 

the “Table to Excel” tool. This method retains all the attribute table information for the feature.

7.5 Error Logs

The CFDT recursively checks outputs for feature line cutbacks and maintains a record 

of transects in the study area where feature delineation was impossible. To display cross-shore 

transects where feature line cutbacks were detected, navigate to the “Data” folder and drag the 

“CutbackTransects” shapefile with the appropriate series name into the main map panel (fig. 12). 

The “Delete Cutbacks” CFDT option in section 5.2.13 automatically removes cliff feature cutbacks, along with any other section of cliff feature line that comes into the vicinity of a flagged 

cutback transect. If no transect features are displayed on the map when adding the “CutbackTransects” shapefile, no feature line cutbacks were detected during processing. 

Additionally, the “Tables” folder in the working directory contains a “TransectErrorRecords” comma-separated values file (.csv) listing any other transects where errors were encountered during feature delineation. The file can be opened in Microsoft Excel or any text editor, or 

it can be added to the main map panel. View the entries in ArcMap by right-clicking on the file 

in the “Table of Contents” and selecting “Open.” For this table, the “RIF” column corresponds 

to a respective cross-shore transect (the “FMF” column on the “3D Transects” attribute table). A 

short explanation of the problem encountered is provided in the “ErrorType” column. The “ErrorCode” column is for internal use by the tool script.

7.6 Intermediate Outputs

Some intermediate outputs generated during processing are kept in the “Scratch,” 

“Scratch.gdb,” and “Tables” folders in the CFDT working directory after each processing run. 

These outputs are useful during troubleshooting; when errors or unusual outputs are recognized, 

a user can add intermediate outputs to the mapping panel and review their attribute tables, which 

can provide clues regarding when and why anomalies were generated. The file names are also 

directly cross-referenced in the tool script, so a user can open the script file and determine which 

processes an intermediate output was associated with. Intermediate outputs are not appended 

with a series name, therefore they are overwritten during each subsequent processing run. 

Acknowledgments

Thanks go to the GIS and Python Knowledge Base Help Group at the USGS, including 

Shane Wright, Marc Hunter, Gregory Cocks, and Curtis Price. This group offered critical debugging advice for aspects of the CFDT and Baseline Builder Tool. Thanks also go to Kyle Glaws, 

who supported the development of cliff feature delineation at the USGS with an earlier, semiautomated tool that used related algorithmic logic. 
51

References Cited

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issue no. 12, chap. 21, p. 299–309. [Also available at https://www.jstor.org/stable/25735606.] 

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of Photogrammetry, Remote Sensing and Spatial Information Sciences, XX ISPRS Congress, 

commission III, v. XXXV-B3, p. 1097–1102, accessed August 23, 2019, at 

https://www.isprs.org/proceedings/XXXV/congress/comm3/papers/430.pdf.

Di, K., Wang, J., Ma R., and Li, R., 2003, Automatic shoreline extraction from high-resolution 

IKONOS satellite imagery, in Proceedings, ASPRS Annual Conference, 2003, Anchorage, 

Alaska—Technology—Converging at the Top of the World, May 5–9: Bethesda, Md., American Society for Photogrammetry and Remote Sensing, 12 p. [Also available at: 

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https://doi.org/10.1130/0016-7606(1982)93%3C644:SCTPPA%3E2.0.CO;2.

Griggs, G.B., and Patsch, K., 2004, California’s coastal cliffs and bluffs, in Hampton, M.A., and 

Griggs, G.B., eds., Formation, evolution, and stability of coastal cliffs—Status and trends: 

U.S. Geological Survey Professional Paper 1693, p. 53–64, accessed May 05, 2019, at 

https://doi.org/10.3133/pp1693.

Hapke, C., and Plant, N., 2010, Predicting coastal cliff erosion using a Bayesian probabilistic 

model: Marine Geology, v. 278, nos. 1–4, p. 140–149. [Also available at: 

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abs/2018AGUFMEP13A..05H/abstract.

Hapke, C.J., and Reid, D., 2007, The National assessment of shoreline change, part 4—Historical coastal cliff retreat along the California coast: U.S. Geological Survey Open-File Report 2007–1133, 51 p., accessed April 25, 2019, at https://doi.org/10.3133/ofr20071133.

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Young, A., 2016, Automatic delineation of seacliff limits using lidar-derived high-resolution 

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Ruggiero, P., Kratzmann, M.G., Himmelstoss, E.A., Reid, D., Allan, J., and Kaminsky, G., 2013, 

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Glossary

Glossary

Baseline Builder Tool A software tool that automatically generates offshore baselines adjacent 

to the seacliffs represented in a DEM, satisfying a required input for the Cliff Feature Delineation 

Tool that would otherwise necessitate manual digitization.

Baseline Distance A Baseline Builder Tool input representing the desired seaward distance, in 

meters, between the cliff face and the offshore baseline.

Baseline Smoothing Tolerance An optional parameter in the Baseline Builder Tool that specifies 

the extent of smoothing performed on a baseline before it is processed by the CFDT.

Basic Delineation A cliff delineation mode of the CFDT that uses the vertical distance from the 

primary chord line to identify cliff top and toe features.

Cliff Feature Delineation Tool (CFDT) Software designed to speed the spatial delineation of cliff 

morphology while removing the potential for variable human interpretation, ultimately making 

outputs more repeatable.

Cliff Height The minimum height, in meters, of cliffs that are to be classified in the study area 

using the Baseline Builder Tool.

Delete Cutbacks An error-handling option in the CFDT that deletes any cliff feature lines that 

cut back on themselves.

Delineation Mode An input that determines which and how many algorithms in the CFDT are 

used to identify final cliff features.

Filter Type A control that allows the selection of one of the two elevation filtering types that can 

be used to generate a baseline in the Baseline Builder Tool: “Automatic” or “Elevation Threshold.”

First Concavity A refinement method in the CFDT that identifies a cliff toe by projecting a 

chord line between the coarsely delineated toe and the cliff midline and then running a one-dimensional slope-analysis kernel across the elevation profile surface between the toe and midline.

Flag Cutbacks An error-handling option in the CFDT that flags regions where cliff feature lines 

cut back on themselves rather than simply deleting the features.

High Pass A refinement method in the CFDT that identifies the cliff toe by analyzing a highpass profile of the beach and cliff.

High Pass Threshold A control in the CFDT that allows a user to tune cliff toe delineation during the high-pass refinement method.

Input DEM The DEM input into the Baseline Builder Tool containing the cliff features from 

which the baseline should be built seaward; it is the same raster DEM that is to be used for cliff 

feature delineation in the CFDT.

Kernel Size An input that modifies the size of the one-dimensional analysis kernel used in “First 

Concavity” toe refinement and “Subsidiary Feature Delineation.”

Landward Distance A CFDT input that indicates the distance in meters that the cross-shore transect projects landward from the offshore baseline.

Maximum Elevation Threshold A filter setting in the Baseline Builder Tool that causes polylines 

occurring above a given elevation to be filtered out of baseline results under the “Manual Threshold” filter-type setting and is unavailable under the “Automatic” filter-type setting.
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Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide

Minimum Elevation Threshold A filter setting in the Baseline Builder Tool that causes polylines 

occurring below a given elevation to be filtered out of baseline results under the “Manual Threshold” filter-type setting and is unavailable under the “Automatic” filter-type setting.

Multi Delineation A delineation mode in the CFDT that executes all 3 delineation methods for 

the cliff toe.

Neighborhood The size, in meters, of the 2D kernel size used in the Baseline Builder Tool to 

scan the DEM for the user-specified “Cliff Height.”

Offshore Baseline A polyline generated by the Baseline Builder Tool, or manually digitized, 

that runs alongshore and seaward of the seacliff features to be delineated. This polyline is a prerequisite for running the CFDT.

Output Cleanup An input in the CFDT that determines how to handle feature line cutbacks 

or regions where more than one cliff top-toe instance is identified along a single cross-section 

profile.

Output Name The file name suffix given to the output digitization guide or automatic baseline. 

All outputs use the name format “AutoBase_OutputName.shp”.

Output Smoothing Tolerance An input into the CFDT measured in meters that determines the 

level of smoothing performed on output cliff feature lines.

Refined Delineation Outputs cliff tops and midpoints as with “Basic Delineation,” but cliff toes 

are derived from a selected “Refined Delineation” method.

Refinement Method One of two options available for toe-position refinement in the CFDT: 

“High Pass” or “First Concavity.”

Seaward Distance A CFDT input that indicates the distance in meters that the cross-shore transect projects seaward from the offshore baseline.

Series Name A CFDT input that adds a user-specified suffix to the names of final model outputs 

for the purpose of identifying tool results from one run to the next.

Smooth Baseline An input that determines whether the CFDT smooths the input baseline before 

it proceeds with cliff feature identification.

Smoothing Tolerance A Baseline Builder Tool input, in meters, that controls the smoothness of 

the curvature for output baselines.

Subsidiary Feature Delineation A selectable CFDT mode that identifies convexities and concavities across the cliff face other than the cliff top and toe using a one-dimensional analysis kernel.

Transect Interval An input in the CFDT that defines the distance in meters, along the offshore 

baseline, between generated transects.

Seymour and others—Cliff Feature Delineation Tool and Baseline Builder Tool, Version 1.0 User Guide—Open-File Report 2020–1070

ISSN 2331-1258 (online)

https://doi.org/10.3133/ofr20201070