This document discusses breaklines, which are linear features that control the behavior of terrain and hydrological modeling. There are two main types of breaklines - traditional breaklines that define terrain features like cliffs and roads, and hydro-enforced breaklines that define streams, ponds, and ditches. The document explains how breaklines are collected, common issues, and provides examples of breakline specifications for projects in Wichita, KS and Missouri that were used for flood mapping and hydrological modeling. It demonstrates how breaklines improve the accuracy of digital terrain models, contours, and hydrological modeling results compared to when breaklines are not used.

1. Breaklines: What Are They
and How Are They Used
March 4, 2010

2. Presentation Overview
 Breaklines – What Are They
 Breakline Issues
 Breaklines for Digital Terrain Model Development
 Breaklines for Contour Development
 Example Project Breakline Specifications
 Water Resources Applications – ESRI Arc Hydro Extension
 Results without Breaklines
 Results with Breaklines

3. Breaklines
What Are Breaklines and
Why Are They Needed?

4. Breakline Definition
 Reflect abrupt changes in the terrain and
control surface behavior by acting as a
barrier to the interpolation of a TIN model
 Breaklines enhance the accuracy of the
surface model in areas where LiDAR points
are not adequate to accurately depict the
surface.
 One driver of contour aesthetic properties
 Generally two types of breaklines
 Traditional breakline features to meet
accuracy specification
 Cliffs, ridgelines, hydro features, road
edges, levees and retaining walls – not
used as much as in the past
 Hydro-enforced breaklines to define the
hydrology,
 Streams, ponds, lakes, ditches – becoming
more common
 Some overlap between the two types

5. Breakline Collection Approaches
Photogrammetric
 Traditional approach
 Utilizes stereo models
(3D)
 Aerial imagery
 Date doesn’t
match LiDAR
 Requires two
lines of sight
 LiDARgrammetry -
LiDAR intensity
images
 Can be expensive

6. Breakline Collection Approaches (cont.)
Heads-up (2D)
 Horizontal placement based
on LiDAR
 Bare-earth LIDAR for
vertical (Z)
 Very effective terrain
modeling in vegetated areas
 Requires only one line of sight
 Less costly in development
vs. traditional methods
 Faster than traditional
methods
 Meets FEMA surface
accuracy requirements

7. Hydro Breaklines
 Hydro breaklines allow for DTM
development that provides
accurate terrain for watershed
modeling, hydraulic & hydrologic
modeling, stormwater and
drainage area delineation, and
stream channel geomorphology
studies
 Enforce stream channels and
ditches into DTM
 Breaklines go around islands in
rivers, lakes, etc.
 Waterbodies are flattened

8. Dual vs. Single Breaklines

9. Dual Line Breaklines
 Upper part of the
channel has no
breaklines
 Lower part of the
channel has dual
breaklines
 River channel flatten with
breaklines on each side
of the channel at waters
edge

10. Hydro Breaklines - Waterbodies
 Waterbodies usually
have a breakline
compiled around the
water’s edge
 LiDAR points inside
breakline are
reclassified and
waterbody is
flattened – same
elevation
 Thisis done for TIN
creation, DTM
generation, contour
development, and
aesthetic

11. Breakline Issues

12. Hydro Connectors
 Culverts
and Dam Outlets – Special
Considerations
Hydro connectors shown as yellow lines

13. Breaklines for Braided Rivers
 Braided rivers
create special
problems,
specifications
need to be
defined
 Treatas multiple
dual breaklines
Platte River in Nebraska

14. Breaklines for Braided Rivers (cont.)
Platte River in Nebraska

15. Breaklines and Wetlands
DEM DTM
 How should
wetlands be
handled?
 Breakline only
around water,
don’t include
vegetation?

16. Buffer Around Breaklines
 Use a buffer to remove bare-earth
points around breaklines,
otherwise artificial dams are
created
 Recommend 5-ft outside buffer
(based on our experience)

17. Breaklines and Digital
Terrain Model Development

18. DTM Results
No breaklines
Breakline enforced

19. DTM Quality (cont.)
With LiDAR data, if breaklines
are not specified, hydro features
will not be as well defined, can
cause modeling errors
With Breaklines
Without Breaklines

20. Breaklines and
Contour Development

21. Contour Results – DEM vs DTM
Contours without breaklines Contours with breaklines

22. Contour Results – 1-ft Interval
Contours without
breaklines
Contours with breaklines

23. Breakline Project
Samples

24. Example Project – Wichita/Sedgwick County, KS
Breaklines Specifications
Linear Features – rivers,
streams, ditches
 Minimum length = 200 ft
 Double line breakline –
channels over 4 ft wide at
base
 Breaklines around islands
 Single line stream breaklines
under 4 ft wide at base
 Stream channel breaklines
only at water/land interface
 Culverts & dam outlets – hydro
connectors – separate feature
class

25. Wichita Example Breaklines for Waterbodies
Waterbodies: Lakes, Ponds (¼ acre or larger)

26. Wichita Example – Other Breaklines
Traditional Breaklines
 Edge of pavement
breaklines along
major roads
 Breaklines
along
top of dams, levees,
dikes

27. Wichita Example – Breakline Density

28. Wichita Example – Breakline Deliverables
 ESRI Geodatabase
 Dataset
 Feature Classes

29. Missouri Example – LiDAR for Flood
Mapping
Hydro-Enforced
Breaklines Only
 Minimum length of 300-
ft
 Breaklines z-values
from bare-earth LiDAR
 Dual breaklines for
streams/ditches > 2-
meters
 Single breaklines for
streams/ditches < 2-
meters
 Stream/ditch breaklines
cut through culverts and
dam outlets

30. Missouri Example – LiDAR for Flood
Mapping (cont.)
 Waterbody breaklines for ½ acre or greater

31. Missouri Example - Breakline Density

32. Missouri Example – Breakline Deliverables
 Shapefiles
 Linear features – includes streams, rivers, ditches
 Polygons - waterbodies

33. Water Resources Applications:
ESRI Arc Hydro Drainage Line Comparison

34. DEM vs Hydro DTM
DEM
Hydro DTM

35. Fill Grid Using DEM & Arc Hydro Drainage
Lines

36. Hydro Breaklines and Hydro Connectors

37. Hydro Fill Grid and Arc Hydro Drainage
Lines
 Dark blue
lines – Arc
Hydro
Drainage
Lines
 YellowLines
– Hydro
Connectors

38. Arc Hydro Drainage Line Comparison
 Dark blue
lines – with
breaklines
 Cyan lines –
without
breaklines
 Yellowlines
– Hydro
Connectors

39. Arc Hydro Catchment Comparison
 Redlines –
catchments
from DEM
 Yellow
lines –
catchments
from DTM
 DTM is
background

40. Arc Hydro Comparison Results #2
 Dark blue
lines – with
breaklines
 Cyan lines
– without
breaklines
 Yellow
Lines -
Hydro
Connectors
 Results
show flow
in different
directions

41. Final Thoughts
When do you need breaklines?
Types of breaklines?

42. Questions
Kenny Legleiter
Senior Government Account Manager
303-353-3837
Kenny.legleiter@merrick.com