Cause studies in which remote sensing techniques were adapted to assist in the solution of particular problem situations in Texas involving vegetation are described. In each case, the final sensing technique developed for operational use by the concerned organizations employed photographic sensors which were optimized through studies of the spectral reflectance characteristics of the vegetation species and background conditions unique to the problem being considered. The three examples described are: (1) Assisting Aquatic Plant Monitoring and Control; (2) Improving Vegetation Utilization in Urban Planning; and (3) Enforcing the Quarantine of Diseased Crops

Benton, A. R., Jr.

Haas, R. H.

Rouse, J. W., Jr.

Toler, R. W.

English

NASA Technical Reports Server

THREE EXAMPLES OF APPLIED REMOTE SENSING OF VEGETATION* L-19
J. W. Rouse, Jr., A. R. Benton, Jr., R. W. Toler
R. H. Haas
Texas A§M University
College Station, Texas
SUMMARY
This paper describes three very different cases
in which remote sensing techniques were adapted to assist
in the solution of particular problem situations in Texas
involving vegetation. In each case, the final sensing
technique developed for operational use by the concerned
organizations employed photographic sensors which were
optimized through studies of the spectral reflectance char-
acteristics of the vegetation species and background condi-
tions unique to the problem being considered. The three
examples described are: (1) Assisting Aquatic Plant
Monitoring and Control; (2) Improving Vegetation Utilization
in Urban Planning; and (3) Enforcing the Quarantine of
Diseased Crops.
ASSISTING AQUATIC PLANT MONITORING AND CONTROL
Concept
The infestation and rapid growth of aquatic plants
in Texas reservoirs has become a serious state problem.
*Supported by NASA Grant NGL 44-001-001.
1797
https://ntrs.nasa.gov/search.jsp?R=19760010481 2020-03-22T16:16:37+00:00Z
These plants have adverse effects on navigation, flood
control and drainage, fish and wildlife, recreation, public
health, and water quality. The growth and spread of these
plants is so dynamic that it has been impossible to monitor
and control the infestation by conventional means. The
Texas Parks and Wildlife Department, with major funding
assistance from the Corps of Engineers, has initiated
systematic chemical spray programs costing over $50,000
annually in an effort to eliminate the problem (over $300,000
total expenditure in Texas to date), but the program has
been only marginally successful and the aquatic infestation
is still spreading each year within affected lakes and into
new lakes. It was hypothesized that use of remote sensing
techniques could aid in monitoring the species type and
growth rate, and in determining more optimum periods and
locations for application of chemical sprays.
Procedure
Color and color infrared photography was selected
as the basic sensing technique. It was determined that
processing control for the films had to be far more stringent
than in most work with this approach to assure acquisition
of reliable temporal measurements. Repeated flights over an
extensive aquatic plant region of Lake Livingston in east
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AQUATIC PLANT MONITORING - Lake Livingston, Texas; east end of
Jungle area, showing old river channel at right. Area to right
of channel is land; area to left is water covered by water
hyacinth and duckweed. (Black and white reduction of color
infrared transparency).
AQUATIC PLANT MONITORING - Entrance to Beacon Bay Marina.
Cloudy patches offshore are areas of hydrilla infestation.
(Enlargement of color infrared transparency).
1799
Texas were performed, with supporting ground observations,
to develop acceptable flight parameters, exposure settings,
film processing procedures, and interpretation guides. Sig-
natures of surface species were shown to provide adequate
differentiation, however species such as hydrilla, coontail,
and myriphyllum, which have both submersed and emersed
states, often require temporal data to insure discrimination
when submersed. The procedure established requires careful
control of the sensing technique and use of sequential pho-
tography throughout the growing season.
Results
The sequential photography showed that there is no
single period of youth, maturity, or senescence in the
aquatic plants in Texas lakes. Newly emergent areas con-
tinually appear, even in mid-to-late season, both on the
fringes of mature patches and in completely new areas of the
lake. In the case of water hyacinth, new areas of youthful
activity reoccur in areas where the mature plants have been
sprayed with chemical herbicide. These findings account for
the lack of success often experienced with the present her-
bicide application program.
Sequential imaging showing the effects of herbi-
cide stress indicated repeated patterns of distinct stress
1800
bands, dieback, occasional disappearance of the vegetation
mat, reemergence of the youthful plants, and steady and
vigorous regrowth in the sprayed areas.
The findings included the following:
- Aquatic plants in Texas lakes are very dynamic
systems.
- The seasonal evolution of aquatic plants can be
monitored by remote sensing techniques. An esti-
mate of aquatic plant biomass may be feasible.
- The maximum value of the remote sensing approach
may be in the accurate monitoring of the effects of
chemical herbicide treatments (and probably biologi-
cal control agents as well) on plant status and
regrowth.
- Evidence was found that application of the herbicide
2,4-D in the concentrations presently used may be
counterproductive for long-range plant control.
- LANDSAT imagery is useful in nonitoring seasonal
growth of hyacinth and duckweed in large lakes
with known infestations.
- Hydrilla, a particularly noxious aquatic plant
species, has been identified on color and color
infrared photography and is now known to exist
in Lake Livingston.
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Payoff
The imagery collected as part of this project
has been presented to the Trinity River Authority, Texas
Parks Department, Texas Water Quality Board, and EPA.
Representatives of these agencies were advised of the docu-
mented dynamic proportions of the aquatic plant problem in
Texas lakes and of the evidence found that the current con-
trol program was inadequate to eliminate the spread of these
plants. One of the agencies responsible for the control pro-
gram in Lake Livingston, the Trinity River Authority (TRA),
reevaluated their approach and have adopted a systematic
remote sensing survey of the lake for their 1975 season
plant control program. The technique developed in this proj-
ect will be employed during 1975 by Texas A§M University
under contract to the Trinity River Authority. These data
will also be employed by the Texas Parks and Wildlife
Department as part of their chemical spray program. The
1975 work is a pilot project for subsequent application of
the approach to other lakes in Texas.
IMPROVING VEGETATION UTILIZATION IN URBAN PLANNING
Concept
The Federal Government has authorized the develop-
ment of certain entirely new planned communities as an experiment
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in urban planning with minimum environmental impact. The
Woodlands is one of these Title VII communities located 28
miles north of Houston, Texas in Montgomery County. In pre-
paration for this development, Mitchell Associates began com-
piling extensive background information on the 17,776 acre
construction site. This included geologic, topographic,
water resources, and soil maps and surveys of wildlife resources,
These data were formatted as a series of thematic maps and
overlays. An attempt was made to acquire sufficient vegeta-
tion information using ground survey techniques in order to
supplement these maps. However, it was found that because
of the quantity and quality of vegetation information required
to support the project planning activities, the ground survey
methods were inadequate. It was hypothesized that aerial
remote sensing techniques could be used to provide satisfac-
tory vegetation species identification and vegetation distri-
bution maps more rapidly and at less cost than existing methods.
Procedure
The nature of the information required dictated
that a ground survey approach must be employed during the
initial stages. The objective of the remote sensing pro-
cedure developed was to optimize the ground survey and
considerably reduce the intensity of the ground sampling.
1803
THE WOODLANDS - Initial development area, showing vegetation
types, recreational facilities and cultural features. (Black
and white reduction from color infrared transparency).
\ - ... - - U
...
M»r>
'•..- ».; ««
M»B
 I9>; •""
THE WOODLANDS - Section of vegetation - cultural map made
from color infrared photos.
1804
This was accomplished by employing a photo interpretation
grid-sampling procedure with color and color infrared
photography acquired at a scale of 1:6000. Tests with black
and white film and with several grid-sampling methods were
conducted prior to developing an acceptably reliable approach.
Results
Color and color infrared photography was used to
prepare vegetation maps of critical portions of the Woodlands
construction sites. The maps showed location, species, size,
and relative health of the vegetation in the area. Ground
sampling was substantially reduced, and it was found that
an extension of the technique to new areas could be done
reliably with virtually no ground verification. A series of
vegetation maps were constructed using sequential photography.
The sequential photos proved to be useful in
recording construction progress and the impact of construc-
tion activities on the vegetation. The definition obtainable
from the 1:6000 scale photos allowed examination of indivi-
dual trees and clumps of underbrush. This gave the developer
insight into the undesirable environmental effects of common
construction practices. To this end, the developer evolved
a system of protective fences and barricades to prevent trees
from being barked, shrubs from being overrun, and root systems
1805
from being overcompacted. In certain cases, subcontractors
were taken off the project because of damage they had done
to the vegetation.
Payoff
The vegetation maps prepared by the Remote Sensing
Center were incorporated into the construction planning
documents for the Woodlands. These data were used to select
the locations of commercial buildings, homes, and roads within
the site. The specific benefits obtained as a direct result
of the use of these vegetation maps included:
- reduced landscaping costs due to the extensive
utilization of the natural vegetation.
- reduced need for artificial drainage systems because
of the maintenance of natural ground cover in select
areas.
- increased land value and greater profit per acre
of development due to limited construction-related
environmental degradation.
The remote sensing procedure developed offers the
additional advantage that environmental damage due to
urbanization can be monitored in a rapid, cost-effective
manner. The general methodology developed in this project
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has been adopted by the Woodlands developer for his future
urban planning activities.
ENFORCING THE QUARANTINE OF DISEASED CROPS
Concept
St. Augustine grass is the primary turf used for
lawns and pasture throughout the South. Ninety-six percent
of the lawns along the Texas Gulf Coast are St. Augustine.
This turf grass was attacked by a strain of Panicum Mosaic
Virus, termed St. Augustine Decline (SAD), beginning in the
mid-1960's. The damage caused by the virus has been exten-
sive to both homeowners and commercial growers in Texas.
Consequently, the Texas Department of Agriculture (TDA) has
quarantined all commercial farms pending development of a
SAD-resistant grass species. The quarantine has been costly
and only partially successful. The TDA spends in excess of
$10,000 each year just to survey the diseased crops. The
manual survey process requires more than six weeks to com-
plete. An improved survey technique and a more effective
quarantine enforcement procedure was needed. It was
hypothesized that remote sensing techniques could assist
with this state problem.
1807
Procedure
A project was initiated by the Remote Sensing
Center in cooperation with the Johnson Space Center to
determine a remote sensing technique for the early, reliable
detection of SAD virus symptoms. Greenhouse samples, test
plots, and commercial fields were measured. Initial results
of both spectrophotometer and spectroradiometer readings
indicated little spectral signature differences between
healthy and diseased grasses in the infrared region and only
slight differences in the green region. However, the use of
light polarizers showed significant differences in light
reflectance in both the red and blue portions of the spectrum.
The aerial detection method subsequently developed
consisted of four Hasselblad cameras with polarizers using
Plus-X film with red, green, and blue filters and black-and-
white infrared film with an 89B IR filter.
Results
During the spring of 1974, the Texas Department
of Agriculture requested that the Remote Sensing Center fly
a SAD detection mission over commercial fields in south Texas.
The area included farms that were known to have SAD infested
crops. These farmers had been requested by TDA to plow under
the diseased areas. However, the farmers had not been responsive
1808
ST. AUGUSTINE DECLINE - Pan American University Campus,
lawns infected with St. Augustine Decline, Diseased areas
are detectable and intensities differentiable on the original
color transparency.
ST. AUGUSTINE DECLINE - NASA truck-mounted spectroradiometer
measuring control plantings of SAD-diseased and healthy turf.
1809
to the request and the IDA Quarantine Division was aware
of attempts to illegally harvest and ship some of the
diseased turf. The farmers were notified by letter from
the IDA that their farms would be overflown during March 1974
for the purpose of remote sensing SAD infected areas. On
March 4, 1974, just prior to the scheduled flights, a visual
inspection of the suspect commercial farms confirmed that
all SAD infected grass areas had been voluntarily destroyed
by the growers.
Payoff
Whereas the commercial turf grass growers in Texas
realized that the existing manual inspection techniques of
the TDA were inadequate to enable TDA to properly enforce
the state-wide quarantine, the advent of an aerial remote
sensing technique convinced the growers that the quarantine
could be effectively enforced and, hence, they chose to
comply with the TDA regulations.
As a result of this project activity, the Texas
Department of Agriculture now has available a reliable,
cost-effective remote sensing technique for surveying and
enforcing quarantine restrictions on the Texas turf producers.
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Three examples of applied remote sensing of vegetation

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