EROSION AND AGRICULTURAL PRACTICES
THAMES RIVER BASIN
An Experience '77 Program carried out under the direction of the
Agriculture and Land Use Subcommittee
THAMES RIVER IMPLEMENTATION COMMITTEE
April, 1978
Representation - Agriculture and Land Use Sub-committee
R. Heard, Ministry of Agriculture and Food, London, Ontario
McFadden, Ministry of Natural Resources, London, Ontario
C. Schenk, Ministry of the Environment, London, Ontario
Thompson, Ontario Federation of Agriculture, R. R. # 1, Blenheim, Ontario.
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS
i
BACKGROUND
1
STUDY SCOPE AND SURVEY METHODOLOGY
Terms of Reference
Field Survey Methodology
4
4
5
SURVEY RESULTS
Introduction
Survey Results by Sub-Basin Area
Lower Thames
Central Thames
South Thames
North Thames
8
8
12
12
12
14
16
OBSERVATIONS
20
RELEVANT LITERATURE
33
APPENDIX
I
II
Watercourses Surveyed by Sub-Basin Area
Sample Field Sheet.
39
40
ILLUSTRATIONS
Page
MAPS:
Map No. 1
Map No. 2
Watercourses Surveyed: Thames River Basin
Survey Results - Thames River Basin
9
19
Survey Results by Sub-Basin Area
11
TABLE:
Table 1
PHOTOGRAPHS
Photo
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
No.
Removal of the forest cover accelerates stream-bank erosion.
Erosion along the Lower Thames River.
Cattle access to watercourses.
Close cropping along the margins of drains.
Erosion of a drain near Highgate.
Erosion from cattle access and poor drainage practices.
Vegetative buffers along watercourses.
Exposed stream and ditch banks.
Emphasis on row crops.
Contour plowing a beneficial practice.
Fertilizer application.
Crop residues prevent erosion.
Use of vegetative cover on ditch banks.
The results of poor drainage practices.
Effect of inadequate tile outlets.
Properly constructed tile outlets.
13
13
15
15
17
17
21
21
24
24
27
27
29
29
30
30
ACKNOWLEDGEMENTS
The Agriculture and Land Use Sub-committee of the Thames River Implementation
Committee gratefully acknowledges the assistance of the following individuals,
organizations and ministries in the preparation of the report on Erosion and Agricultural
Practices in the Thames River Basin:
-
The Upper and Lower Thames Conservation Authorities, the Woodstock office of the
Ontario Ministry of Agriculture and Food and the Corporation of the Town of St.
Marys for providing office facilities for field personnel.
-
Messrs. B. Hann, L. Kerr, P. Agar, G. Agar and K. Thompson for personal and
practical insights respecting erosion problems and farm practices.
-
Professor M. Troughton, D. Graves and other members of the cartography section
and staff of the map library of the Department of Geography, University of Western
Ontario, for providing professional guidance, mapping advice and assistance.
-
Messrs. I. Baskett (Milk Marketing-Board), J. Brent, D. Agar, I. Kennedy and Mrs.
J. Ryan of the Ontario Ministry of Agriculture and Food for providing information on
dairy cattle operations and general advice on agricultural problems and practices.
-
R. A. Forsyth, D. A. Taylor, A. W. Scott, H. W. Buck and A. N. Watson, Agricultural
Representatives of the Ontario Ministry of Agriculture and Food; Dr. G. J. Wall,
Department of Land Resource Science, University of Guelph; Mrs. K. Knapp; J. B.
Connor, University of Toronto; C. Piper, Maitland River Conservation Authority; and
Messrs. T. Phillips, M. Blythe and W. Baskerville of the Long Point Region
Conservation Authority for general advice and assistance.
i
-
All members of the farm community within the Thames River Basin whose
co-operation facilitated the work of the field survey crews.
-
J. F. Longworth of the Ministry of the Environment and Mrs. R. Chalk who shared
the responsibility for the field supervision of students involved in the project, the
compilation of data and the preparation of this report
-
And most importantly, the following Experience '77 students who were responsible
for the collection of field data so essential to the development of the information
base:
Monica Betz, Lambeth, Ontario
Fern Cole, Thorndale, Ontario
Dianne Corbett, Ailsa Craig, Ontario
Susan Devaux, Brockville, Ontario
Jill Easter, Brockville, Ontario
William Groombridge, Waterloo, Ontario
Robert Innes, St. Paul's Station, Ontario
Dorothea Kanter, Dorchester, Ontario
Lyle Long, Lambeth, Ontario
Mary McTavish, Gadshill, Ontario
Charlene Peat, Norwich, Ontario
Marlene Platten, Fenelon Falls, Ontario
Louise Ridley, St. Marys, Ontario
Robert Wilkins, London, Ontario
ii
BACKGROUND
This report on "Erosion and Agricultural Practices" is an outcome of the Thames
River Basin Water Management Study undertaken jointly by the Ministries of Environment
and Natural Resources. The latter study was initiated in response to water quality, flooding
and erosion problems throughout the watershed and their implications for future
population growth, economic development and land use practices.
Although previous independent studies had been undertaken by the Upper Thames
River Conservation Authority, the Lower Thames Valley Conservation Authority, the
Province and municipalities within the watershed, it became increasingly apparent that the
complexity and interrelated nature of water resource problems required a co-ordinated and
multi-disciplinary approach to their identification and resolution. Consequently, the Ontario
Ministries of the Environment and Natural Resources undertook a detailed and
comprehensive study of the Thames River watershed in 1972.
The resulting report entitled "Water Management Study - Thames River Basin",
contained 29 recommendations dealing with problems of water quality and management,
flood control and urban and agricultural land use.
In order to address these problems, the study recommended the establishment of
a joint committee. In the fall of 1976, the Thames River Implementation Committee
(T.R.I.C.) was formed with representation from the following:
Ministry of the Environment
Ministry of Natural Resources
Ministry of Agriculture and Food
Ministry of Treasury, Economics and Intergovernmental Affairs
1
Ministry of Housing
Upper Thames River Conservation Authority
Lower Thames Valley Conservation Authority
Association of Municipal Engineers
Federation of Agriculture
Because of the diversity of the problems identified, three sub-committees were
established to investigate and report on specific recommendations.
The Agriculture and Land Use Sub-committee was assigned responsibility for ten
recommendations contained in the Water Management Study, three of which (nos. 12, 20
and 27) became the subject of further attention in the summer of 1977. These three
recommendations are as follows:
12.
"A program of restricting free access of livestock to streams should be
commenced. It is recommended that the Department (sic. Ministry) of
Agriculture and Food take the lead role in undertaking a detailed study of the
implications of such a program to farmers; of the best methods such as
fencing or vegetative barriers; and of the feasibility of provincial subsidies to
encourage such a program."
20.
"Soil erosion control programs including strip cropping, crop rotation,
diversion terraces, grassed waterways and vegetative buffer zones or
reforestation should be implemented throughout the watershed with initial
emphasis on areas that should be identified by staff of the Ministries of
Agriculture and Food, Natural Resources and Environment."
27.
For long-term flood control, flow augmentation and erosion control benefits,
it is recommended that sound conservation measures such as reforestation,
2
sound agricultural tillage, use of appropriate ground cover and preservation
of water retaining areas be encouraged and implemented. Reforestation and
establishment of shrub cover along stream banks should be directed to areas
where they would specifically aid in erosion control, streambank stabilization
and the improvement of fish habitat."
In order to fully address the matters identified in recommendation 27, the
subcommittee broadened its perspective to include the impact of artificial drainage works
on water retention areas and erosion.
As a means of documenting the incidence and severity of certain of the problems
identified in the foregoing recommendations and for the purpose of substantiating the
need for remedial measures, the sub-committee initiated a field survey during the summer
of 1977 utilizing students acquired under the Experience '77 program.
3
STUDY SCOPE AND SURVEY METHODOLOGY
TERMS OF REFERENCE
The following terms of reference were established defining the scope of the study
and the field data requirements for the watercourses surveyed within the Thames River
watershed:
a)
To record the nature, location and lineal extent of soil erosion along
streambanks and artificial drainage courses.
b)
To determine the extent and location of points of cattle access to
watercourses and the extent to which such access has contributed to
streambank erosion.
c)
To identify land uses adjacent to the watercourses that are inconsistent with
sound conservation practices with particular emphasis on cropping to stream
margins, the removal of vegetative buffers and tillage practices inconsistent
with accepted soil conservation measures.
d)
To formulate a coding system to record field data for subsequent
transposition to suitable base mapping.
e)
To provide photographic documentation of illustrative problem areas.
f)
To identify serious problems contributing to water quality impairment
requiring immediate remedial action.
g)
To research relevant technical reports including the preparation of a
4
bibliography of significant literature.
h)
To develop a descriptive catalogue of the field data recording system.
i)
To prepare a written synopsis of the information collected in the field.
FIELD SURVEY METHODOLOGY
Under the auspices of the Ontario Experience '77 program, 15 university students
with a geography and/or farm background were hired jointly for a fourteen week period
by the Ministries of the Environment and Natural Resources and the two Conservation
Authorities, to carry out the necessary field survey. Four survey teams were established
and assigned responsibility for the respective sub-basins comprising the Thames River
watershed.
Because of the extensive area of the watershed, total coverage of all watercourses
was not possible during the employment period. Consequently the following criteria were
applied as a basis for defining priorities:
a)
Watercourses identified in the Thames River Basin study as having high
levels of BOD, coliforms, nitrogen and phosphorus were accorded first
priority.
b)
Following completion of the aforementioned watercourses, one creek within
each nutrient sub-basin as defined in the parent study was surveyed with
respect to the incidence of cattle access, the adequacy of stream buffers and
the extent of erosion to permit possible subsequent correlation with water
quality monitoring systems.
5
c)
Watercourses selected for study were surveyed commencing with the
headwaters. A complete data base respecting cattle access, bank erosion,
and the adequacy of stream buffers was established for each.
Commencement at the headwaters of each stream was intended to ensure
that areas upstream from small population centres were covered within the
limited time period in response to their identification in the parent study as
significant sources of pollution.
d)
The Thames River itself was accorded a lower priority due to time constraints
and the fact that the main watercourse has been the subject of previous
studies.
The watercourses included in the survey are listed in Appendix I.
Data were recorded on a standardized field sheet (see Appendix II) and on
topographic mapping having a scale of 1:25,000, for each of the sub-basin areas
comprising the total watershed.
Each field data sheet describes a section of the watercourse that is numerically and
geographically keyed to the relevant topographic map. The data sheet identifies the name
and/or nature of the watercourse e.g., tributary, municipal drain; the adjacent land use
and the dimension of vegetative buffers; the presence, lineal extent and probable cause
of streambank erosion e.g., gullying, discharge of drainage tiles, slumping, cattle access;
the proximity of other pollution sources to the watercourse e.g., feedlots, poultry
operations; and a visual assessment of water quality.
For purposes of graphic illustration, field data were subsequently transposed to
"single factor" overlay maps. For a detailed description of each site however, reference
must be made to the respective field data sheets.
6
Information pertaining to the survey is retained on file at the Ministry of the Environment,
985 Adelaide Street South, London, Ontario and is available for scrutiny or use by anyone
interested in the detailed results of the program.
As a precautionary note, the Committee wishes to emphasize that the data collected
reflect only the conditions that existed during the summer of 1977 and are therefore
subject to change. Although every attempt was made to minimize subjectivity through the
use of a standardized field sheet, variations in the students' perception of the problem and
the approximation of distances must be recognized as a limitation by those intending to
make subsequent use of the data for other purposes.
7
SURVEY RESULTS
INTRODUCTION
The field survey carried out during the summer of 1977 covered all or part of 32
different tributary watercourses in addition to sections of the Thames River itself. Although
time did not permit every watercourse to be surveyed, the number and distribution of
those completed was considered sufficient to be representative of the Thames River basin
as a whole.
In order to distribute the work of the field crews, the survey results were collected
and tabulated separately for each of four sub-basin areas referred to as the Lower, Central,
South and North Thames. The boundaries of the sub-basins, the name and location of the
watercourses surveyed and the survey results, are shown on Map 1 and Table 1,
respectively.
Data contained in Table I entitled "Survey Results by Sub Basin Area" address the
study's three principal areas of concern viz., erosion, stream buffers and cattle access to
watercourses.
Column 1 of the Table indicates the total miles of watercourse surveyed. This figure
is twice the actual length of the watercourse since the data respecting erosion and stream
buffers apply to both banks.
Column 2 refers to the total miles of eroded bank as evidenced by slumping,
undercutting or other natural causes and from cattle access. Column 3 indicates the
percentage of streambank eroded relative to the total number of miles surveyed within the
sub-basin.
8
9-A
9-B
Column 4 indicates the number of miles of watercourse where cropping has
occurred closer than 5 feet to the top of the stream bank i.e., the vegetative buffer is less
than 5 feet. Although this distance is an arbitrary one, it was considered to represent the
minimum width necessary to intercept nutrients and suspended particles during periods
of heavy runoff and reduce the likelihood of bank slumping caused by the encroachment
of heavy farm machinery.
The effectiveness of this distance will vary however, depending on the bank stability
and profile, the susceptibility of differing soils to erosion, the nature of adjoining crops and
tillage practices and finally, the characteristics of the vegetative cover itself. For example,
sand loam soils would be more susceptible to slumping than heavy clay and therefore
require a wider buffer, whereas a buffer consisting of trees and shrubs would constitute
a more effective means of stabilizing the bank and impeding cattle access than a grass
cover functioning solely as a nutrient and sediment trap. The percentage of total
watercourse length having less than the minimum buffer is shown in column 5.
Column 6 deals with cattle access and records the number of sightings of livestock
observed at or within watercourses as well as other physical evidence of their presence.
The bottom row of the Table aggregates the sub-basin area data to illustrate the
extent of the problem for the Thames River basin as a whole.
Following is a brief description of the survey results for each of the sub-basins
together with a concluding observation on variations throughout the entire watershed.
10
TABLE1.
Survey Results By Sub-basin Area
Miles of
Total Miles
Miles
Surveyed
Eroded
Lower Thames
339
249
74
292
86
27
Central Thames
366
193
53
150
41
99
South Thames
1114
230
21
117
11
321
North Thames
1369
382
28
104
8
678
Total:
3188
1054
33
664
21
1125
(1)
(2)
(3)
(4)
(5)
(6)
Sub-Basin Name
%
Buffers
%
< 5 Ft.
11
Cattle
Access
SURVEY RESULTS BY SUB-BASIN AREA
1.
LOWER THAMES
The Lower Thames sub-basin falls primarily within the County of Kent. Three
watercourses were surveyed having a combined length of 339 miles. The principal
characteristics of this watershed are the emphasis on the production of cash crops
and the extensive use of tile drains necessitated by the flat topography and
inherently poor natural drainage of the predominantly clay soils. As a result, many
of the tributaries within the upper reaches of the watercourses consisted of
municipal drains fed by field tiles. Because of the intensity of crop production, the
prevailing tendency was to crop close to the margins of drains and natural
watercourses. Consequently, this sub-basin displayed the highest percentage of
eroded streambank and buffers less than 5 feet, i.e., 74% and 86% respectively.
In contrast however, evidence of cattle access was the lowest in the Thames
watershed.
2.
CENTRAL THAMES
The Central Thames sub-basin falls primarily within the County of Elgin and the
southwesterly portion of the County of Middlesex. Five watercourses were surveyed
having a total length of 366 miles. This sub-basin contains a mixture of clay soils
and sand over clay with the latter predominating in the westerly and northeasterly
portion and the former occurring to the north and east. Since the sand layer is thin,
the underlying clay impedes the natural drainage and field tiles and municipal drains
comprise the upper reaches of many tributaries. Cash cropping is not as intensive
as in the Lower Thames and the basin exhibits a transition to more general
agriculture and livestock production.
12
Photo 1.
Removal of the forest cover from the margins of the Medway River leaves the
streambank vulnerable to the erosive action of water and eventual undercutting.
The root structure of trees and shrubs can bind soil particles together and retard the
rate and severity of natural erosion.
Photo 2.
Poorly constructed tile outlets, cropping too close to the bank, the removal of
stabilizing vegetation or a combination of all three may have been responsible for
this serious example of erosion along the Lower Thames River.
13
Evidence of cattle access was almost four times greater than in the Lower Thames.
Slightly more than half of the total watercourse length surveyed exhibited evidence
of erosion (53%) whereas approximately two-fifths (41%) had buffers less than the
five-foot minimum.
3.
SOUTH THAMES
The South Thames sub-basin falls primarily within the southerly portion of the
County of Middlesex and includes the majority of the County of Oxford. Fourteen
watercourses were surveyed within this area representing a total length of 1,114
miles or slightly more than one-third of the total. Much of the sub-basin consists of
till plains characterized by loam soils and exhibits greater topographic variations
than the sub-basin to the west. Since the soils themselves have excellent natural
drainage, there are fewer municipal drains and a corresponding smaller percentage
of erosion (21%) and stream buffers less than the minimum* (11%). Since this
sub-basin borders the City of London and other principal urban centres in and
adjacent to the two counties, there is an increasing emphasis on dairying as
reflected in the higher figures respecting cattle access.
____________________
*
There is likely a greater tendency to crop closer to a straight drain than a meandering
natural watercourse.
14
Photo 3.
Unrestricted cattle access to watercourses is a major contributor to streambank
erosion and the impairment of water quality.
Photo 4.
The practice of cropping close to municipal drains reduces the width and
effectiveness of stream buffers to Intercept soil particles and nutrients. The result
is sedimentation and weed growth necessitating premature cleaning.
15
4.
NORTH THAMES
The North Thames sub—basin corresponds generally to the central portion of
Middlesex County north of London and much of the County of Perth. Twelve
streams were surveyed comprising a total length of 1369 miles. Topographically,
this area is similar to the South Thames although variations in relief are not as
pronounced. This similarity is reflected in the relatively low percentages of eroded
streambank (28%) and buffer areas less than the minimum (8%). Evidence of cattle
access however, was the highest of all sub-basin areas. An emphasis on cattle
farming in this area accounts for the low percentage of inadequate stream buffers
since herds are often pastured within floodplain areas and along steeply sloping
banks unsuitable for crop production.
Aggregating the data for each of the sub-basin areas indicates that one-third of the
total length of all watercourses surveyed showed evidence of erosion; slightly more than
one-fifth was subject to close cropping practices and exhibited buffers of less than 5 feet;
and a total of slightly more than 1100 occurrences of cattle access were recorded during
the course of the field survey. In the absence of any accepted yardsticks, it is not possible
to comment on the severity of the problems. However, the data derived from the field
survey quantifies the relative magnitude of perceivable agricultural influences on water
quality and demonstrates that the nature, extent and intensity of the problems vary
throughout the Thames River Basin as a whole.
16
Photo 5.
A combination of steeply sloping banks, a lack of vegetative cover and cattle access
have accelerated the rate of erosion resulting in sedimentation and impairment of
this drain near Highgate.
Photo 6.
The trampling of the stream banks by cattle has destroyed the vegetative cover
leaving the banks exposed to the erosive action of water. This problem is
compounded by a poorly constructed tile outlet resulting in incipient gullying.
17
Map No. 2, "Survey Results -Thames River Basin", graphically illustrates by
sub-basin, the data obtained from the Table except for livestock access. In the latter case,
the potential for livestock access is reflected by numbers indicating the actual distribution
of dairy cattle. Similar information on the number of beef cattle was not readily available.
At any rate, it becomes apparent from an examination of the map that bank erosion and
inadequate buffers are more prevalent in the Lower and Central Thames whereas the
problem of cattle access can be expected to vary in relation to their geographical
distribution.
Assuming that the financial resources necessary to implement any remedial
demonstration programs are limited, this information should prove useful in determining
the most suitable locations for remedial measures that would yield the maximum return
in terms of controlling erosion and cattle access and improving water quality. The means
of accomplishing these objectives without unduly adding to the costs of agricultural
production is currently receiving attention by the Thames River Implementation
Committee.
18
Map No. 2:
SURVEY RESULTS: THAMES RIVER BASIN
19
OBSERVATIONS
The principal purpose of the study has been to identify by means of field survey,
those matters addressed by recommendations 12, 20 and 27 contained in the Water
Management Study - Thames River Basin. Although intended to be primarily descriptive,
the tabulation of survey results would be incomplete without some supplementary
observations respecting the underlying causes of the problems and possible remedial
actions.
Many of these causes are attributable to changes in agricultural practices affecting
the entire Thames River Basin such as the trend to larger mechanized farms and changing
farm economics that dictate an increasing emphasis on the production of cash crops, the
maximizing of arable land and more intensive agricultural operations. It is the purpose of
this concluding section therefore, to examine these trends; identify the resulting farm
practices contributing to soil erosion and other forms of water quality impairment; and to
suggest possible remedial measures and future courses of action.
TRENDS IN AGRICULTURE
In recent years, average farm sizes have increased through consolidation whereas
the acreage devoted to the production of crops has also been expanded by means of
artificial drainage schemes, the removal of fence lines and forest cover and the gradual
reduction of vegetative buffers adjacent to stream margins. This trend is a response to the
mechanization of agriculture and the economic necessity of maximizing the productive
capabilities of large, powerful and expensive farm equipment. These capabilities can only
be achieved with larger fields that can be "worked" with maximum speed and efficiency
by reducing turning motions.
20
Photo 7.
A vegetative buffer should be retained between cropped areas and the watercourse
to serve as a nutrient and sediment trap.
Photo 8.
Removal of the protective vegetative cover exposes the bank to the erosive action
water resulting in gullying and bank slumping.
21
Larger fields however, increase the potential for erosion since the velocity of water
runoff increases with the length of uninterrupted passage. The problem is further
aggravated where row crops are planted transcurrent to the contours and runoff is
channelized.
The larger, faster and more powerful farm machinery also contribute to increasing
soil erosion. Fields may be worked repeatedly and to greater depths, ultimately causing
compaction and thereby affecting the infiltration capacity of the soil. Subsoils containing
a lower organic content are brought to the surface and their lower permeability increases
runoff. Conversely, the pulverization of soils through repeated tillage facilitates the surface
translocation of soil particles to adjacent drains and watercourses.
Where cropping occurs too close to stream margins, heavy farm machinery is
instrumental in the breakdown of banks resulting in their eventual slumping.
The costs of mechanization in particular and farm economics in general have
created pressures on the farmer to maximize yields and financial returns by the planting
of cash crops such as corn and soybeans. Previously marginal lands have been converted
to the production of these crops by the installation of artificial drainage works and fields
have been expanded by clearing wooded areas and reducing the width of vegetative cover
along stream margins. As a further means of maximizing yields, row crops are planted
consecutively and the virtual elimination of crop rotation in some areas has increased the
susceptibility of soils to erosion. The practice of plowing under the residue after removal
of the cash crops and working the land extensively in preparation for spring planting
further exposes the soil to erosion.
22
Heavy applications of commercial fertilizers may also be employed to maintain high
levels of production. Where applications are excessive, surficial runoff results in the
translocation of nutrients to watercourses and the resulting stimulation of aquatic
vegetation. Excessive aquatic plant growth upsets normal oxygen balances necessary to
support aquatic life in watercourses, thus resulting in further impairment of water quality.
Throughout the basin, but particularly in the Lower Thames, the amount of arable
acreage and crop yields have been expanded by the installation of artificial drainage works
consisting of field tiles and open drains. The inherent poor natural drainage of these areas
has been surmounted by the installation of these artifical drainage works, resulting in a
more rapid rate of infiltration and discharge to open drains, higher spring floods,
accelerated streambank erosion and increased sediment loads entering watercourses.
Based on information obtained from the Milk Industry Branch of the Ministry of
Agriculture and Food, approximately 53,000 dairy cattle and 1,100 dairy operations are
situated within the Thames River Basin, the largest concentrations occurring in the North
and South Thames areas.
Dairy operations are heavily concentrated in Oxford and Perth counties whereas the
largest number of beef herders is found in Middlesex County.
In addition to the geographic concentration of cattle, livestock operations per se
have become more intensified. Since 1974, the number of dairy herds in excess of 75 head
more than doubled in the North Thames area. Sightings of cattle access in this area were
numerous in contrast to the Lower Thames.
23
Photo 9.
Where row crops predominate, runoff is channelized increasing soil losses. The rate
of erosion is accelerated where the rows are planted down rather than across the
slope.
Photo 10.
Contour plowing is an effective means of reducing soil losses from sheet and rill
erosion.
24
In addition to the organic pollution and bank erosion resulting from direct cattle
access to watercourses, the impairment of water quality may also occur from the feedlot
itself. A number of examples were recorded of feedlots located too close to watercourses
or tributary drains resulting in surficial runoff of pollutants.
SOIL EROSION
A discussion of soil erosion implies a situation where the rate of precipitation
exceeds the rate of infiltration resulting in runoff. Conservation measures are necessary
therefore, to safely remove surface water without excessive soil loss.
Since the less extreme forms of erosion are frequently imperceptible, a major
problem is convincing individuals that they are in fact occurring. Since sheet and rill
erosion* occur uniformly over a slope, they frequently go unnoticed until a significant
proportion of the productive topsoil has been removed. In contrast, the evidence of gully
and streambank erosion is more pronounced and remedial action accorded a higher
priority.
Although soil losses from fields may be visually imperceptible, a preliminary analysis
of fluvial sedimentation in Ontario suggests that 50% of the annual loads occurs during
the months of highest precipitation viz., March and April.
Since erosion is a natural process, conservation measures can only retard the rate
and severity. Gullies constitute an extreme and advanced form that must be treated in the
early stages. One means of stabilizing the problem is the cessation of cropping and
reversion to a grassed waterway.
______________________
*
Sheet erosion occurs where water runoff is distributed uniformly over a broad expanse of
exposed soil surface. Rill erosion results from rivulets or "small streams" and most
frequently occurs in the cultivation corridors between row crops.
25
In order to reduce soil losses from fields, a vegetative cover or mulch is required
during all seasons. The canopy effect of the cover reduces rain splash and prevents the
resulting soil crusting from inhibiting infiltration.
Contour plowing and strip cropping also retard the velocity of water flow and its
ability to transport soil particles. This conservation practice is particularly important where
fields border watercourses and topographic extremes generate rapid runoff. Another
approach to reducing soil erosion is to spring plow. This is feasible in sandy and gravelly
soils that dry more rapidly and are highly porous.
A winter cover crop constitutes an ideal method of reducing erosion. Where this is
not feasible, the stalks and roots of harvested crops should be left uncultivated.
Excessive working of the soil also facilitates erosion since fine particles are
susceptible to detachment and transportation by both wind and water.
Flow in many of the Thames tributaries originates from field tiles that progress to
open drains prior to discharge to the natural watercourse. Poorly constructed tile outlets
to drains and watercourses are a common occurrence throughout the basin. The most
frequent problems arise from outfalls of insufficient length to prevent the discharge from
eroding the streambank and eventually undercutting the pipe.
Numerous problems were observed with respect to the construction of open drains
particularly where dredging resulted in steeply sloping unstable banks that were devoid of
vegetation and susceptible to erosion. An important consideration in the construction of
drains is the stability of soils. For example, a 1:1 slope may be adequate to ensure bank
26
Photo 11.
Excessive applications of fertilizer, poor tillage practices and a predominance of row
crops combine to increase the potential for water quality impairment.
Photo 12.
Maintaining the crop residue after harvesting is an effective mean of preventing
sheet and rill erosion during the spring freshet.
27
stability in areas of clay soils.* Soils having a high sand content however, may require
slopes of up to 3:1.
Following construction or dredging, steps to reestablish the vegetation on all
disturbed areas should be initiated to capitalize on the availability of soil moisture. The
canopy effect of a vegetative cover in combination with proper bank gradients will reduce
soil losses and eliminate the need for frequent dredging. A combination of Birdsfoot Trefoil
and Creeping Red Fescue is an example of an effective seed mixture for streambank
stabilization. Ditch bank seeding is presently the subject of research at the University of
Guelph and the Ontario College of Agricultural Technology in Ridgetown.
From observations in the field, there is a prevailing tendency to crop close to the
margins of drains and natural watercourses. This practice was especially prevalent in the
Lower Thames where the upper reaches of watercourses consisted mainly of drainage
ditches. In addition to slumping of banks caused by the encroachment of heavy machinery,
the reduction in stream buffers facilitates the access of soil particles and nutrients to the
watercourse. It is worth noting that existing land use control legislation deals with setback
requirements for urban uses but neglects to address similar concerns in agricultural areas.
Soil erosion resulting from cattle access to watercourses is prevalent throughout the
basin with the exception of the Lower Thames area where cash cropping predominates.
_______________
*
A 1:1 slope means 1 lineal unit of horizontal setback for every lineal unit of vertical depth.
For example, where the depth of ditch is 1 foot, the bank would be sloped back an equal
distance. Expressed as an angle, a 1:1 slope is equal to 45 degrees.
28
Photo 13.
Ditching operations should ensure that slopes are not too steep and vegetative
cover is replaced as quickly a possible to avoid ..........
Photo 14
........... erosion, slumping and sedimentation such as are evident along this ditch.
29
Photo 15.
Where field tile outlets are not sufficiently extended, the erosive action of the
discharge eventually undercuts the pipe leading to severe gullying.
Photo 16.
A properly constructed drainage outlet discharges directly to the water thereby
preventing bank erosion.
30
Beef herds tend to be held intensively in feedlot areas whereas dairy cattle may
either be contained intensively or grazed. Where cattle are pastured within the floodplain,
the breakdown of stream banks is a common occurrence.
During periods of high water flow, these banks are more susceptible to the erosive
action of water. Animal wastes also contribute directly to the impairment of water quality
where grazing is practised. The problem is accentuated by increasing herd sizes,
particularly during the summer months when streamflows are low.
To combat erosion, gravel cross-overs have been employed as a means of limiting
the number of access points since cattle exhibit a preference for the gently sloping gravel
bank. Complete fencing has also been recommended coupled with the construction of
watering ponds and dugouts. Since fencing could involve substantial costs to the farmer,
the feasibility of this approach may be dependent on financial subsidies.
As an alternative to grazing, many farmers are intensively feeding their cattle.
Unless the feedlots are properly located and sound manure management practices are
followed, water quality impairment may occur where feedlot runoff gains direct access to
a drain or natural watercourse. Feedlots are more susceptible to runoff since soils are compacted by the concentration of animals thereby reducing their infiltration capacity.
Although the Agricultural Code of Practice addresses proper manure management
techniques, there are no controls respecting the setback of feedlots from watercourses.
In summary, this report has identified a number of agricultural practices resulting
in various forms of soil erosion that contribute to an impairment of water quality.
31
Intensive cash cropping and livestock operations, poor tillage practices, the
improper construction and maintenance of drains, cattle access to watercourses and the
diminution of stream buffers are all contributing factors. The significance of any one factor
however, varies in each of the four sub-basins. Problems arising from drainage works,
inadequate stream buffers and intensive cash cropping have a higher priority in the Lower
Thames area whereas cattle access is more significant in the North and South Thames
areas coupled with a general need for the observance of soil conservation practices
dictated by the more undulating topography.
Hopefully, this study has demonstrated that the problems identified in the Thames
River Basin report exist to an extent warranting a concerted and comprehensive program
of remedial action. Initially, this program might take the form of one or more
demonstration projects applied to tributary watersheds to permit a comparative evaluation
of the impact of remedial measures on water quality. The impetus for such a project
however, will only materialize if there is a recognition and acceptance on behalf of the farm
community that agricultural practices and the maintenance of water quality are interrelated
and that improvements to both are mutually beneficial and essential to the long term
viability of agriculture and the optimization of water use potential.
32
RELEVANT LITERATURE
1.
Bangay, G. E. 1976. Livestock and Poultry Wastes in The Great Lakes Basin:
Environmental Concerns and Management Issues. Social Science Series No. 15,
Environment Canada, Inland Waters Directorate, Ontario Region, Burlington,
Ontario.
2.
Barlow, Thomas. 1977. "Solving the Soil Erosion Problem." Journal of Soil and Water
Conservation. Soil Conservation Society of America. 32(3):146-192.
3.
Bone, Samuel W., et al. Ohio Erosion Control and Sediment Pollution Abatement
Guide for Agricultural Land. Co-operative Extension Service/Ohio State University,
Bulletin 59.
4.
Buckman, Harry O. and Nyle C. Brady. 1969. The Nature and Properties of Soils.
Seventh Edition, Macmillan Company: London.
5.
Charng-Ning, Chen. 1974. Planning Tools for Erosion
Control in Urbanizing
Watersheds. Proceedings: New Hampshire Conference on Urban Runoff Quality and
Quantity.
6.
Dickinson, W. T., A. Scott, G. Wall. 1975. "Fluvial Sedimentation in Southern
Ontario." Canadian Journal of Earth Sciences. The National Research Council of
Canada. 12(11):1813-1819.
7.
Dickinson, W. T., G. J. Wall. No Date. "A Statement re- The Influence of Land Use
on Erosion and Transfer Processes of Sediment."
8.
Dickinson, W. T., G. J. Wall. 1976. "Temporal Pattern of Erosion and Fluvial
Sedimentation in the Great Lakes Basin." Geoscience Canada, 3(3):158-163.
33
9.
Dickinson, W. T., 1977. "Careless Cropping Practices Contributing to Soil Erosion."
London Free Press, October , 1977.
10.
Environmental Protection Agency. 1971. Agricultural Pollution in the Great Lakes
Basin. Washington, U. S. Printing Office.
11.
Forster, D. Lynn. 1975. "Simulated Beef Feed Lot Behaviour Under Alternative Water
Pollution Control Rules." American Journal of Agriculture Economics.
12.
Found, W. C., A. R. Hill, E. S. Spence. 1976. "Economic and Environmental Impacts
of Agricultural Land Drainage in Ontario." Journal of Soil and Water Conservation.
January-February:(20-24).
13.
Gifford, Gerald F., Richard H. Hawkins. 1976. "Grazing Systems and Watershed
Management: A look at the Record." Journal of Soil and Water Conservation.
NovemberDecember:281-282.
14.
Grant, Kenneth E. 1975. "Erosion in 1973-74: The Record and the Challenge."
Journal of Soil and. Water Conservation. January-February:(29-32).
15.
Gray, Stephen, L. 1970. Eutrophication: Factors Affecting it, Ways of Measuring it,
Ways of Reducing it. Publication No. ES-14, Institute of Environmental Sciences and
Engineering, University of Toronto.
16.
Haussmann, F. C. 1975. Thames River Basin Water Management Study Technical
Report: The Public Consultation Program. Ontario Ministry of the Environment.
34
17.
Hoover, J. R., G. O. Schwab. 1968. "How Drain Spacing and Crop Sequence Affect
Tile Flow." Reprinted from Ohio Report, 53(5):73-74.
18.
Kasal, James. 1976. Trade-Offs Between Farm Income and Selected Environmental
Indicators: A Case Study
of Soil Loss, Fertilizer, and Land Use Constraints.
Economic Research Service, United States, Department of Agriculture, Technical
Bulletin No. 1550.
19.
Keeney, Dennis R., Kwang W. Lee, Leo M. Walsh. 1975. Guidelines for the
Application of Wastewater Sludge to Agricultural land in Wisconsin. Technical
Bulletin No. 88, Department of Natural Resources, Madison, Wisconsin.
20.
Ketcheson, J. W. 1977. "Why Plow?" London Free Press. October, 1977.
21.
Messih, S. Population and Land Use in the Thames River Basin. S. Earn, ed. Land
Use Co-ordination and Special Studies Section, Environmental Approvals Branch,
Ministry of the Environment.
22.
Moldenhauer, W. C., C. A. Onstad. 1975. "Achieving Specified Soil Loss Levels."
Journal of Soil and Water Conservation. July-August:(166-168).
23.
Ontario Ministry of Agriculture and Food. 1975. 1975 Field Crop Recommendations.
Publication No. 296.
24.
Ontario Ministry of Agriculture and Food. 1975. Agricultural Statistics for Ontario,
1975. Publication No. 20, Prepared by Statistics Section, Economics Branch.
35
25.
Ontario Ministry of Agriculture and Food, Ontario Ministry of the Environment,
Ontario Ministry of Housing. 1976. Agricultural Code of Practice.
26.
Ontario Ministry of the Environment. 1975. Water Management Study: Thames
River Basin.
27.
Phillips, Ted. 1977. Report on Vegetative Municipal Drain Stabilization Trials in
Former Windham Township within
the Watershed of the Long Point Region
Conservation Authority. Long Point Region Conservation Authority, Simcoe, Ontario.
28.
Ontario Ministry of the Environment. 1975. Water Management Study Summary
Report: Thames River Basin.
29.
Ripley, P. O., William Kalbfleisch, S. J. Bourget, D. J. Cooper. 1961. Soil Erosion by
Water: Cause, Damage Control. Canada Department of Agriculture, Publication
1083.
30.
Seitz, W. D., R. G. F. Spitze. 1973. "Environmentalizing Agricultural Production
Control Policies." Journal of Soil and Water Conservation. March-April:(61-64).
31.
Select Committee on Land Drainage. 1974. Agricultural Land Drainage in Ontario.
Final Report of the Select Committee on Land Drainage. Fourth Session, 29th
Legislature; 23 Elizabeth II.
32.
Soil Conservation Service, U. S. Department of Agriculture. 1973. Drainage of
Agricultural land: A Practical Handbook for the Planning, Design, Construction and
Maintenance of Agricultural Drainage Systems. Water Information Centre: Port
Washington, New York.
36
33.
Van Haverbeke, David F., Leon Chesnin, David R. Miller. 1976. "Feed Lot Waste
Runoff and Mortality of Windbreak Trees." Journal of Soil and Water Conservation,
JanuaryFebruary:14-17.
34.
Van Vliet, L. J. P., G. J. Wall, W. T. Dickinson. 1976. "The Effect of Agricultural Land
Use on Potential Sheet Erosion Losses in Southern Ontario." Canadian Journal of
Soil Science. 56:433-451.
35.
Walker, R. L. and Partners, Consulting Engineers and Economists. 1974.
"Sedimentation and Pollution of Watercourses. Contribution of Sediments and Other
Pollutants to Receiving Waters from Major Urban Land Development Activities."
Ottawa.
36.
Webber, L. R., J. H. Lane. 1969. "The Nitrogen Problem in the Land Disposal of
Liquid Manure." Paper presented at the Animal Waste Management Conference,
Syracuse, New York.
37.
White, Richard K., et al. Ohio Livestock Management Guide. Co-operative Extension
Service, Ohio State University, Bulletin 604.
38.
Whitely, H. R. 1973. "The Farm Operator as Water Manager." Notes on Agriculture.
Guelph, Ontario Agricultural College, IX (1).
39.
Wischmeier, W. H. 1976. "Use and Misuse of the Universal Soil Loss Equation: The
Equation's Developer Offers Some Do's and Don't's in Using this Soil Conservation
Planning Tool." Journal of Soil and Water Conservation. January-February.
37
40.
Woodruff, N. P., Leon Lyles, J. D. Dickerson, D. V. Armbrust. 1974. "Using Cattle
Feedlot Manure to Control Wind Erosion." Journal of Soil and Water Conservation,
May-June: 127-129.
41.
Zovne, Jerome, J., Theodore A. Bean, James K. Koelliker, John A. Anschutz. 1977.
"Model to Evaluate Feed Lot Runoff Control Systems." Journal of the Irrigation and
Drainage Division, 103 (IRI): 79-92.
38
APPENDIX I
WATERCOURSES SURVEYED BY SUB-BASIN AREA
North Thames
North Thames River
Whirl Creek
Black Creek
Avon River
Otter Creek
Trout Creek
Gregory Creek
Wye Creek
Stoney Creek
Medway River
Fish Creek
Flat Creek
South Thames
Pottersburg Creek
Waubuno Creek
Middle Thames River
Holiday Creek
North Branch Creek
Mud Creek
Phelan Creek
Cedar Creek
Deer Creek
Reynolds Creek
Dingman Creek
Sharon Creek
Oxbow Creek
Thames River
Central Thames
Cornwall Creek
Fleming Creek
Newbiggin Creek
Gentleman Creek
Thames River
Lower Thames
MacGregor Creek
Proctor Drain
Tilbury Creek
39
APPENDIX II
THAMES RIVER BASIN STUDY
FIELD DATA SHEETS
TOPO SHEET NAME:
AERIAL PHOTO #:
SITE:
DATE:
TIME:
TEAM MEMBERS:
1)
WATERCOURSE(Name of Watercourse, if any)
Tributary
River
Municipal Drain
Drain Meandering? Yes, ________
No _________
2)
LAND USE
Location
Feet
Land Use
A
B
C
(Land Uses: Barren, Grass, Scrub, Wooded,
Cultivated or Cropped)
3)
EROSION
(a)
Gullying
(b)
length __________ ft.
depth __________ ft.
Other Types
(i)
(ii)
(iii)
undercutting
slumping
cattle erosion
-
Yes __________
Yes __________
Yes __________
No __________
No __________
No __________
trampling down bank
breaking down bank
evidence:
Yes _____
Yes _____
No _____
No _____
-
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
footprints
dung
paths
cattle seen
pastured woodlot
40
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
APPENDIX II (cont’d)
3)
(c)
Extent of Erosion
i)
ii)
iii)
4)
length of shoreline affected
height of erosion on bank
are trees sliding in
Is there a feedlot in close proximity to the watercourse?
Yes _____ No _____
5)
___________ ft.
___________ ft.
Yes _____ No _____
WATER QUALITY (check one)
Clear
Semi-Turbid
Murky
ADDITIONAL COMMENTS:
41