This study analyzed over 1600 streamlined glacial landforms in Connecticut using LiDAR data and GIS analyses. Key findings include: 1) Drumlin orientations are locally controlled by topography but generally follow regional trends likely set by glacial lobes. 2) Till deposits are found on the up-flow and down-flow sides of obstructions in high relief areas. 3) In high relief areas, drumlin asymmetry is controlled by local topography and drumlin size by the space between hilltops.

1. Analyses of Streamlined Till Deposits
Drumlin measurement comparisons
Drumlin Orientation
Asymmetry
Understanding controls on Connecticut drumlin morphology, location, and orientation using LiDAR and GIS analyses
Ken BOLING and Michael WIZEVICH
Central Connecticut State University bolingkes@ccsu.edu
Understanding controls on Connecticut drumlin morphology, location, and orientation using LiDAR and GIS analyses
Ken BOLING and Michael WIZEVICH
Central Connecticut State University bolingkes@ccsu.edu
Conclusions
References
• Drumlin orientations appear be locally affected by topography (local relief)
while following a general regional trend. The regional trends of drumlin axis
directions appear to be controlled on a scale larger, possibly on the glacial lobe
scale.
• Till deposits tend to occur on the up-flow and down-flow sides of
obstructions in areas of high relief.
• In areas of high relief, drumlin asymmetry is controlled by the local
topographic morphology.
• In areas of high relief, drumlin size is controlled by the inter-hilltop space.
• LiDAR is a useful tool for delineating the morphology of drumlins and other
glacial features.
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Introduction
The surficial material in Connecticut was deposited primarily during
the Quaternary glaciations. Much of this material occurs as till deposits, some of
which have been streamlined to form drumlins. The analysis of these landforms
may reveal important information about the paleoglacial conditions which
produced them. These landforms were mapped by the USGS in 2001 using air
photo based contour maps. Recently, a set of high resolution digital elevation
models (DEM) produced from the Connecticut LiDAR (Light Detection And
Ranging, an optical remote sensing technology) data collected in 2000 was
released. However, a state-wide analysis of these features using this data has not
been done.
This study integrated the LiDAR DEMs with 10 ft. horizontal
resolution and 1 ft. vertical resolution obtained from the CLEAR website
(http://clear.uconn.edu.) Over 1600 streamlined features were mapped over the
state of Connecticut, an area of 14,356 km2. Streamlined till features were then
separated into categories based on their morphology and relation to bedrock
obstacles. The morphologic type, morphometry, orientation, and location of these
forms were analyzed and compared to the original Quaternary map produced by
the USGS and bedrock geologic map of Connecticut.
Examining the map of drumlin long-axis orientations (Fig. 4a), several flow patterns become apparent. The
orientations of the drumlins in the western and eastern highlands are generally northwest to southeast, however in the
central Hartford basin the drumlin orientations are northeast to southwest. This is also seen when comparing drumlin
elevations with axis direction (Fig. 4b).
It is commonly stated that the shape of a drumlin is an indicator of flow
direction, such that they have a longer down-flow side and a shorter up-flow side. This is
apparently not true for the Connecticut drumlins. Drumlins in Connecticut are equally
disposed to be oriented with the steeper side in the up-flow or the down-flow direction. The
reason for this variation in asymmetry appears to be due to differences in the elevation of
each side. Drumlins occurring on the up-flow side of an obstruction tend to have a shorter
down-flow side than drumlins on the down-flow side of obstructions (Fig. 6).
Stone, J.R., Schafer, J.P., London, E.H., DiGiaronno, M.L., Lewis, R., and Thompson, W.B.,
2000, Quaternary map of Connecticut and Long island sound basin: U.S. Geological Survey,
scale 1:125000 sheet 1 of 2.
Clark, C.D.; Hughes, Anna L.C.; Greenwood, Sarah L.; Spagnolo, Matteo; Ng, Felix S.L.. 2009
Size and shape characteristics of drumlins, derived from a large sample, and associated scaling
laws. Quaternary Science Reviews, 28 (7-8). 677-692.
Figure 3a. Drumlin field in northwest Connecticut. These drumlins
sit at a high elevation on top of high-relief, hard metamorphic
bedrock. Till is easily differentiated from bedrock; till deposits
appear smoother and lack jointing or structural patterns.
Classifications of Drumlin Morphology
Full LiDAR map of Connecticut, Colorized for elevation, compiled from
115 quadrangle maps downloaded from the CLEAR site.
h
Methodology
Each streamlined till feature identified in the survey was manually
digitized using ArcGIS software. Two line features representing the long axis and
width measurements, as well as a point feature at the highest elevation along the axis
were created for each drumlin. The width and highest point were determined using a
5-ft contour map generated from the LiDAR DEM. The long axis was determined
using an “aspect” map, which assigns each slope direction in the DEM a different
color, making the central axis readily apparent (Fig. 1). The actual spatial values for
these data points were then interpolated directly from these created features, using
the LiDAR DEMs as a base to calculate elevation. The advantage to this approach is
that the DEM contains detailed elevation data which can be determined for any
point.
Figure 1. Drumlin axes can easily be determined using an aspect map to
show the point where the direction of the slope is reversed.
Classic Drumlin-
Streamlined till deposit that
forms a topographic high
point relative to the
surrounding area. It has a
relatively smooth and
regular surface. It has a base
that is clearly
distinguishable from
surrounding drumlins and
does not appear to be
associated with bed rock.
Figure 2a. classic drumlin with high
symmetry on the western side of the
central valley.
Down-Flow Obstruction
Till Accumulation-
Streamlined till deposits that
occur on the down-flow side
of a bedrock obstruction to
flow.
Figure 2c. Feature occurring on the
down-flow side of a basalt ridge that
obstructed flow.
Figure 2b. Several drumlins on top of a
large till deposit on the eastern side of
the valley.
Complex Drumlins-
Drumlins that occur together
in large complexes, and
have bases which are
indistinguishable from one
another.
Irregular streamlined
deposits – Streamlined till
deposits which are similar in
appearance to drumlins but
do not fit into the other
categories due to their
apparent association with
underlying bedrock, possibly
due to their thickness.
Figure 2e. Highly irregular streamlined
deposits, occurring in an area of high
relief, shown in aspect.
Up-flow obstruction till
accumulation- streamlined
till deposits which occur on
the up-flow side of an a
bedrock obstruction to flow.
Figure 2d. Streamlined till deposits
occurring on the up-flow side of an
obstruction, shown here on an aspect map.
Due to the variety and complexity of the streamlined till
deposits mapped in this survey, it was necessary to organize
them into categories:
•Complex Drumlins
•Classic Drumlins
•Down-Flow Obstruction Till Accumulations
•Up-Flow Obstruction Till Accumulations
•Irregular
After mapping and categorizing these features, several regional trends became apparent. The drumlins in the
northern part of the basin are mostly classic drumlins, except for the complexes on the eastern edge of the basin (Fig. 3d)
While in the southern areas of the basin, drumlins tend to form small complexes on the up-flow sides of the basalt ridges, but
are absent on the down-flow sides. The most densely populated drumlin fields occur in the metamorphic highlands(Fig. 3a and
3b). Both of these fields occur on the down-flow side of regional-scale metamorphic ridges. Obstructions seem to control the
locations of till accumulation (Fig. 3c).
Figure 3b. Drumlin field in northeast Connecticut. Drumlins occur
on top of bedrock ridges that appear to be controlled by structural
trends. They mainly occur together with indistinguishable bases
(drumlin complexes).
Figure 3c. Drumlins on top of thick till deposits that accumulated
on both the up-flow and down-flow sides of a ridge-forming
granitic gneiss.
Figure 3d. Classic drumlins in the Mesozoic Hartford rift basin
sit on the low relief, relatively soft sedimentary rock. These
drumlins are very regular, but some have been modified by
processes when surrounded by glacial Lake Hitchcock. The
complexes of drumlins on the eastern edge of the basin sit at a
higher elevation.
Several morphometric variables were determined for each drumlin, including length, width, elongation ratio
(length/width), up and down-flow axis angles, underlying rock type, axis direction, elevations at the highest point and end
points of the drumlin axis, and asymmetry ratio (up-flow distance / down-flow distance). These values were then analyzed
to determine any relationships.
The most frequently referenced drumlin attribute is the length / width ratio, which is believed to indicate ice-
flow velocity. For this study the length / width ratio did not appear to have any spatial pattern, however plotting the length
against the width yields a graph very similar to those produced in a different study (Clark , 2009).
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
200 220 240 260 280 300 320 340 360
Elevation(ft)
Direction (Polar degrees)
elevation vs direction
Stand-Alone
Complex
Down-Flow
Obstruction
Up-flow
Obstruction
Rock-
Associated
0.01
0.10
1.00
10.00
0.00 0.50 1.00 1.50 2.00
Asymetryratio(log)
Front / back elevation ratio
Asymetryvs elevation ratio
Stand-Alone
complex
Down-Flow Obstruction
Up-Flow Obstruction
Irregular
0.0
1000.0
2000.0
3000.0
4000.0
5000.0
6000.0
7000.0
8000.0
9000.0
10000.0
0.0 500.0 1000.0 1500.0 2000.0 2500.0 3000.0
Length
Width
Length vs Width
Stand-Alone
Complex
Down-Flow Obstruction
Up-flow Obstruction
Rock-Associated
Figure 4a. Long-axis azimuth orientations colorized ranging from
green (120o) to red (210o)
Figure 4b. Drumlin elevation plotted
against axis direction. The smaller
grouping at the bottom is the area of the
central basin where the axis direction
changes.
Classic Drumlin
Complex Drumlin
Irregular
Up-flow
Down-flow
Figure 5. drumlin
axis length plotted
against width
Figure 6. Drumlin front/back elevation ratio plotted against asymmetry ratio.
Note that the up-flow and down-flow drumlins are different.