278
J.C. Ritchie
Cihlar (1987) describes techniques for using satellite data (MSS, TM, SPOT) for
monitoring potential sheet and rill soil erosion and conservation practices on agriculturallands. However, he found that image-specific predictive relationships were
required to achieve accurate quantitative results. In most studies, photointerpretation
of satellite images has been most useful for repetitive monitoring and large area
reconnaissance (Johannsen and Barney 1981; Johannsen and Saunders 1984) rather
than gathering infonnation about specific sites. Phillips et al. (1986) discuss the many
potential applications of the Thematic Mapper (TM) to conservation assessment and
concluded that TM is a valuable tool for managing the landscape. With the improving
spectral and spatial resolution of current satellites, satellite data will become even
more important for monitoring pattern and rates of soil erosion across the landscape.
Pelletier and Griffin (1988) used photointerpretation of aerial photographs to identifying conservation practices on agricultural lands. They concluded that CIR aerial
photographs were most useful (see Color Plate 12.A for an example of one of the
photographs used). They estimated that more than 90% of the soil conservation
practices used in the United States could be identified at a photographic scale of
I: 10000 and that 29% could still be identified at a scale of I :80000. Stephens and
Cihlar (1982) provided an interpretation key to identify agricultural practice and soil
erosion features from CIR photographs taken in Canada. They also concluded that
most conservation practices could be identified. Wilson et al. (1989) concluded that
SPOT panchromatic data (10 meters) could be visually interpreted to develop an
effective potential soil loss map while TM imagery could be used to update crop
management practices during the growing season. Such monitoring of conservation
practices with remotely sensed data provides a basis for evaluating the effectiveness
of conservation practices, managing soil erosion control practices on the landscape,
and providing data for input for soil erosion models.
Photogranunetric techniques applied to ground and aerial photographs have been
used to measure changes in surface topography and quantify soil loss rates. Welch and
others (Welch and Jordan 1983; Welch et al. 1983; Thomas and Welch 1988)
describe the application of photogranunetric techniques to quantify soil loss using
ground and aerial photographs. They estimated that photogranunetric techniques (Fig.
12.1)with aerial stereo-pairs could provide X, Y, and Z terrain coordinates with
vertical accuracies of ±25 mm at contour intervals of 150 mm. In a three-year study,
they made quantitative estimates of the amount and pattern of soil eroded or deposited
in a 5.34 ha field. The same photogranunetric techniques have been used to measure
stream channel degradation (Collins and Moon 1979) and the development of rills and
ephemeral gullies in agricultural fields (Thomas and Welch 1988).
Photogranunetic techniques were used with photographs taken at 15 to 30 m above
the ground (Spomer and Mahurin 1984; Spomer et al. 1986) to quantify gully
development and hillslope soil erosion. They measured elevation with an accuracy of
±l5 cm and estimated net soil displacement (erosion minus deposition) to be 46,260,
and 605 Mg ha- 1 respectively for 1972-1974, 1974-1978, and 1978-1984. They
estimated that sediment delivery at the end of the catchment was 53% based of the
photogranunetric study as compared with 21 % computed from USLE estimates. They
concluded that remote sensing provided better estimates of soil loss. Using sequential
J.C. Ritchie
Cihlar (1987) describes techniques for using satellite data (MSS, TM, SPOT) for
monitoring potential sheet and rill soil erosion and conservation practices on agriculturallands. However, he found that image-specific predictive relationships were
required to achieve accurate quantitative results. In most studies, photointerpretation
of satellite images has been most useful for repetitive monitoring and large area
reconnaissance (Johannsen and Barney 1981; Johannsen and Saunders 1984) rather
than gathering infonnation about specific sites. Phillips et al. (1986) discuss the many
potential applications of the Thematic Mapper (TM) to conservation assessment and
concluded that TM is a valuable tool for managing the landscape. With the improving
spectral and spatial resolution of current satellites, satellite data will become even
more important for monitoring pattern and rates of soil erosion across the landscape.
Pelletier and Griffin (1988) used photointerpretation of aerial photographs to identifying conservation practices on agricultural lands. They concluded that CIR aerial
photographs were most useful (see Color Plate 12.A for an example of one of the
photographs used). They estimated that more than 90% of the soil conservation
practices used in the United States could be identified at a photographic scale of
I: 10000 and that 29% could still be identified at a scale of I :80000. Stephens and
Cihlar (1982) provided an interpretation key to identify agricultural practice and soil
erosion features from CIR photographs taken in Canada. They also concluded that
most conservation practices could be identified. Wilson et al. (1989) concluded that
SPOT panchromatic data (10 meters) could be visually interpreted to develop an
effective potential soil loss map while TM imagery could be used to update crop
management practices during the growing season. Such monitoring of conservation
practices with remotely sensed data provides a basis for evaluating the effectiveness
of conservation practices, managing soil erosion control practices on the landscape,
and providing data for input for soil erosion models.
Photogranunetric techniques applied to ground and aerial photographs have been
used to measure changes in surface topography and quantify soil loss rates. Welch and
others (Welch and Jordan 1983; Welch et al. 1983; Thomas and Welch 1988)
describe the application of photogranunetric techniques to quantify soil loss using
ground and aerial photographs. They estimated that photogranunetric techniques (Fig.
12.1)with aerial stereo-pairs could provide X, Y, and Z terrain coordinates with
vertical accuracies of ±25 mm at contour intervals of 150 mm. In a three-year study,
they made quantitative estimates of the amount and pattern of soil eroded or deposited
in a 5.34 ha field. The same photogranunetric techniques have been used to measure
stream channel degradation (Collins and Moon 1979) and the development of rills and
ephemeral gullies in agricultural fields (Thomas and Welch 1988).
Photogranunetic techniques were used with photographs taken at 15 to 30 m above
the ground (Spomer and Mahurin 1984; Spomer et al. 1986) to quantify gully
development and hillslope soil erosion. They measured elevation with an accuracy of
±l5 cm and estimated net soil displacement (erosion minus deposition) to be 46,260,
and 605 Mg ha- 1 respectively for 1972-1974, 1974-1978, and 1978-1984. They
estimated that sediment delivery at the end of the catchment was 53% based of the
photogranunetric study as compared with 21 % computed from USLE estimates. They
concluded that remote sensing provided better estimates of soil loss. Using sequential