Slope Stability in the Marietta Area, 

Washington County, 

Southeastern Ohio 

i 

·I . 

I 

I 

~ ' 

Slope Stability in the Marietta Area, 

Washington County, 

Southeastern Ohio 
Frontispiece: Earth flows and creep along the northeast-facing 

slope 2 kilometers northwest of Stanleyville. 
Slope Stability in the Marietta Area, 

Washington County, 

Southeastern Ohio 

By JOHN S. POMEROY 

An investigation of the distribution of slope movements 

in a part of southeastern Ohicr-a discussion of 

geologic and other factors involved in their genesis 

U.S. GEOLOGICAL SURVEY BULLETIN 1695 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1987 

For sale by the Books and Open-File Reports Section, U.S. Geological Survey, 

Federal Center, Box 25425, Denver, CO 80225 

Library of Congress Cataloging in Publication Data 

Pomeroy, JohnS., 1929-

Siope stability in the Marietta area, Washington County, 

southeastern Ohio. 

(U.S. Geological Survey bulletin; 1695) 

Bibliography: p. 

Supt. of Docs. no.: 119.3:1695 

1. Slopes (Physical geography) -Ohio-Marietta Region. 

2. Earth movements-Ohio-Marietta Region. 

I. Title. II. Series 

QE75.89 no. 1695 557.3 s [551.4'36] 86-600274 

[GB448] 
CONTENTS 

Metric conversion factors VI 

Abstract 1 

Introduction 1 

Terminology 2 

Geology and its relation to slope movements 4 

Clay mineralogy 6 

Methodology 7 

Regional description of slope movements 10 

Area west of Muskingum River 10 

North of Ohio 676 10 

South of Ohio 676 13 

Area between Muskingum River and Duck Creek 15 

West of Interstate 77 15 

North of Ohio 821 15 

South of Ohio 821 18 

East of Interstate 77 20 

Area between Duck Creek and Little Muskingum River 20 

North of Ohio 26 20 

South of Ohio 26 22 

Area south of Little Muskingum River 25 

Discussion of geologic and other factors involved in slope failures 28 

Lithology, stratigraphy, and structure 28 

Slope features 30 

Configuration 30 

Angle-grade 30 

Orientation (aspect) 30 

Surface drainage and the influence of microclimate 31 

Valley stress release 31 

Vegetation 32 

Precipitation 32 

Advice for residents 33 

Identification of a slope failure 33 

Practices that cause slope failures 34 

Remedial actions 35 

Summary 36 

References cited 37 

Appendix 39 

FIGURES 

Frontispiece: Earth flows and creep along the northeast-facing slope 2 kilometers 

northwest of Stanleyville II 

1 . Index maps of Marietta area 2 

2. Features of slope movements 5 

3. Lithologic sections 9 

4. Map of area north of Ohio 676 12 

5. Photograph showing site of slope failure above Gilman Street 13 

Contents V 
FIGURES-Continued 

6. Map of area south of Ohio 676 14 

7-9. Photographs showing slope failures 

7. Rockfall area along Ohio 7 15 

8. Debris slide along Ohio 550 16 

9. Earth flow northwest of Moore Junction 16 

10. Map of area north and west of Ohio 821 17 

11-13. Photographs showing slope failure and drainage channels 

11. Fill and subjacent slope failure along western side of Interstate 77 18 

12. Backyard failure in Devola 18 

13. Ruins of house, east of De vola 18 

14. Graph showing rainfall at Marietta, 1962-83 19 

15. Photograph showing slope drainage channels 20 

16. Map of area south of Ohio 821 21 

17-18. Photographs showing slope failure 

17. Crib failure behind motel, east of Ohio 60 22 

18. Walnut Hills Drive slope movement 22 

19. Map of area east of Interstate 77 and west of Duck Creek 23 

20-22. Photographs showing earth flows 

20. Opposite of Stanleyville 24 

21 . Looking across earth flow 25 

22. Head area of earth flow, east of Ohio 821 25 

23. Map of area north of Ohio 26 26 

24-26. Photographs showing earth flows and earth slump 

24. Head of earth flow 27 

25. Earth flow within concave slope 27 

26. Earth slump along Brush Run 27 

27. Map of area south of Ohio 26 28 

28. Map of area north of Ohio 7 29 

29. Histogram showing orientation of recent slope failures in the Marietta area 30 

30-32. Diagrams showing possible effects of: 

30. Backyard fill placement 34 

31. Lower slope excavation 35 

32. Downspout water on slope 35 

TABLES 

1. Slope-failure-prone soils, estimates of soil properties, and engineering interpretations, Marietta area 8 

2. Summary of selected soil test data and character of underlying bedrock along Interstate 77 10 

3. Aerial photographs used in investigation 11 

Metric Conversion Factors 

Multiply 

metric units 

millimeter (mm) 

centimeter (em) 

meter (m) 

kilometer (km) 

square kilometer (km2) 

cubic meter (m3) 

By 

0.0394 

0.3937 

3.281 

0.621 

0.386 

35.311 

VI Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 

To obtain 

U.S. customary units 

inch (in~ 

inch (inJ 

foot (ft) 

mile (mi) 

square mile (mi2) 

cubic foot (ft3) 
Slope Stability In the Marietta Area, 

Washington County, Southeastern Ohio 

By John S. Pomeroy 

Abstract 

Geologic materials and slopes conducive to naturally 

occurring slope failure abound in the Marietta, Ohio, area. 

About 1,150 recently active earth flows, slumps, debris slides, 

and complex forms of slope failure were mapped within a 

mantle of weathered rock and soil. Earth-flow-type movements 

are the most prominent slope failure forms. Beneath this mantle 

is a thick sequence comprised of the Monongahela Group of 

Pennsylvanian age and the Dunkard Group of Pennsylvanian 

and Permian age. Both of these units contain subhorizontal re,d 

shale and mudstone interbedded with intermittent thin to thick 

sandstone beds. The area was investigated in 1983 and 1984 

to obtain data related to the topographic and geologic setting 

of slope movements. Field data were obtained over a period of 

75 to 80 days along closely spaced traverses in an area of about 

180 square kilometers. 

One large slope movement (approximately 54,000 

square meters) within Marietta has forced the removal of 

18 houses. Another actively moving slope involves a 1 Akilometer-wide area above the Ohio River. A 4.5-squarekilometer forested area southeast of Marietta contains nearly 

90 mappable recent slope failures ranging in size from 100 to 

50,000 square meters. 

Lithologic, geomorphic, and microclimatic factors play 

an important role in the origin and distribution of slope failures. 

Movements in the regolith originate below seeps on slopes of 

low permeability. The slopes most susceptible to movement 

are those overlying relatively thick intervals of shale and mudstone interbedded with thinner intervals of coarser grained 

clastic rock. Slope configuration and angle, aspect, existing 

surface drainage, and the effect of stress release along valley 

walls influence slope failure distribution. 

Beginning in 1970, the Marietta area has been subjected 

to generally greater than normal precipitation resulting in high 

ground-water levels. Long-time residents report an increase in 

slope movements in recent years. The field investigation has 

confirmed the presence of fresh scars above hummocky 

ground along slopes. Most recent movements (about 90 percent) in this largely rural area are initiated by precipitation 

rather than by construction and other slope modifications. 

INTRODUCTION 

The Marietta area (fig. 1), Washington County, 

southeastern Ohio, was investigated during spring 1983 and 

1984 and late fall 1983 to obtain data related to the topographic and geologic setting of slope movements (Pomeroy, 

1984a, b, 1985). The area [about 180 square kilometers 

(km2)] involves most of the Marietta 7112-minute quadrangle 

and parts of the Belmont, Willow Island, Valley Mills, 

Fleming, and Parkersburg 7112-minute quadrangles (fig. 1). 

About 1 0 percent of the area is urbanized. 

The area had been examined briefly in 1978 by Hackman and Thomas (1978) and others as part of a reconnaissance inventory of the entire Appalachian Plateau region 

involving several States. I participated in the field checking 

of the quadrangles in the Marietta area at that time. 

Previous comments about slope problems in the 

Marietta region have been made by Collins and Smith 

(1977) and Ohio State University (1950). A portion of the 

Ohio River shoreline in West Virginia opposite Marietta 

was shown by Lessing and others (1976). Slope stability has 

been discussed in other regions of southeastern and eastern 

Ohio by Everett (1963), Fisher (1969, 1978), Fisher and 

others (1968), Hooper (1969a, b), Hubbard (1908), Lanyon 

and Hall (1983), Lessig (1966), Marshall (1969), Mast 

(1980), Mitchell (1941), Philbrick (1962), Savage (1950, 

1951), Sharpe and Dosch (1942), Sheley (1969), Van 

Buskirk (1977), Waltz and Fisher (1978), and Webb and 

Collins (1967). 

The Marietta area, which lies within the unglaciated 

part of the Appalachian Plateau province, shows a high 

incidence of slope movements typical of the southeastern 

Ohio-western West Virginia-southwestern Pennsylvania 

region. Relief generally is only 91-121 meters (m~ 

markedly less than that in other areas of the Appalachian 

Plateau, which have an average relief of 152-182 m. 

An objective of the current project was to determine 

the areal distribution of slope movements that would lead to 

a better understanding of their topographic and geologic 

setting and of the processes involved. Furthermore, the detailed inventory would enable the investigator to compile a 

slope stability map that would distinguish areas with different potentials for land sliding (U.S. Geological Survey, 

1982, p. 25). The results of the investigation would be applicable to what could be expected in other areas in southeastem Ohio, adjacent West Virginia, and southwestern PennIntroduction 1 
Figure 1. Marietta area. 

400 

Cincinnati 

Figure 1 A. Location of Marietta. 

FLEMING 

C"'un.:htowrP 

0 Columbus 

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W~"ST 

sylvania and, thus, would serve as a prototype for evaluating 

landslide susceptibility in this part of the Appalachian 

Plateau. A basic question to be resolved was the susceptibility to movement of natural, unmodified slopes. 

The selection of the Marietta area was based, in part, 

on the availability of such local sources of information as 

historical data from the Marietta Times and data from the 

Engineering Office of the Ohio Department of Transportation, the Marietta City Engineer's office, the Soil Conservation Service Office, the National Forest Service, and the 

Geology Department at Marietta College. 

Special acknowledgement is extended to Ted Bauer 

(Marietta Times), Robert Jones (Soil Conservation Service), Robert Badger (City Engineer), Richard Delong 

(Ohio Geological Survey), Clayton Blaney (Marietta 

Sewage Treatment Plant), and Victor Wolff (District 10, 

Ohio l)epartment of Transportation). The author is grateful 

BELMONT 

"viRGINIA 

0 

Charleston 

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Wheeling I 

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Pittsburgh 

L---------T----

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50 MILES 

I 

0 50 KILOMETERS 

for the opportunity to discuss his observations and interpretations in traverses with Robert Van Horn (Ohio Geological 

Survey), Marilyn Ortt (Marietta botanist), and John 

Batteiger (Marietta Times). 

TERMINOLOGY 

The term "regolith" is used in this report to describe 

material from rock weathered in place (residuum) as well as 

weathered material that has moved downslope (colluvium). 

Although colluvium is commonly at its maximum thickness 

at the base of the slope, it generally is found along all parts 

of the slope. 

The term "mudstone" is used extensively in this report 

rather than "clay-shale'' or "shale," which were used by 

previous workers in southwestern Pennsylvania and in 

southeastern Ohio. Earlier investigators did not differentiate 

2 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
'2 .2 : 

Figure 4 

0 

I I 

1 MILE 

I 

0 1 KILOMETER 

EXPLANATION 

Area included in figure 

---- Boundary of mapped area 

4 Lithologic sections (fig. 3) 

308 Soil test data (table 2) 

Figure 1 B. Location of maps used in this report. 

between bedded shale and nonbedded mudstone. Berryhill 

and others ( 1971) and Collins and Smith ( 1977) stated that 

mudstone is a more appropriate term than shale for most of 

these fine-grained clastic rocks because the rocks commonly 

lack fissility and are essentially nonbedded. Only where the 

rocks are bedded or fissile should they be called shale. 

A claystone is a clay-rich mudstone. The following definitions of rock types (Gary and others, 1972) are cited here: 

Claystone.-lndurated clay having the texture and composition of shale but lacking its fine lamination and fissility; 

a massive mudstone in which the clay predominates over 

silt. Most claystone is thin and seldom exceeds a few 

meters in thickness and includes underclay beneath a coal 

bed. 

Terminology 3 
Mudstone.- Indurated mud having the texture and composition of shale but lacking its fine lamination and fissility; 

a blocky or massive fine-grained sedimentary rock in 

which the proportions of clay and silt are approximately 

the same; or a general term that should be used only 

where the amounts of clay and silt are not known or 

cannot be identified precisely. Mudstone is not as fine 

grained as claystone, is more abundant in the stratigraphic section, and has greater maximum thickness. 

Shale.- Fine-grained indurated detrital sedimentary rock 

formed by the consolidation of clay, silt, or mud and 

characterized by finely stratified structure and (or) fissility that is approximately parallel to the bedding. 

The term "landslide" has been used widely as an allinclusive term for almost all types of slope movements including some that involve little or no sliding (Varnes, 1978, 

p. 11). In this report, I have used the general term "slope 

movement" rather than landslide except for movements that 

involve only sliding and have used landslide wherever shear 

failure occurs along a specific or multiple surfaces (Varnes, 

1978). 

Following the classification of Varnes (1978, 

fig. 2.1), slope movements in the Marietta area include falls 

(rockfalls), slides (earth and rock slumps, debris slides), 

flows (debris flows, earth flows, debris avalanches, soil 

creep), and complex movements (slump-earth flows, debris 

slide-earth flows) (figs. 2A-C). 

Rockfalls are extremely rapid [greater than 3 meters 

per second (m/s)] free falls of bedrock. Alternating competent and incompetent lithologies, in addition to closely 

spaced vertical joints parallel to the drainage, are contributing factors to the process. Slides are either slumps or debris 

slides. Rock slumps and earth slumps are characterized by 

rotational movement with an upward-curving rupture surface, whereas debris slides take place along planar or mildly 

undulatory surfaces and are called translational movements. 

Slide movements can be very slow [1.5 meters per year 

(m/yr)] to rapid [0.3 meter per minute (m/min)]. Flows are 

of. four types ranging in movement from extremely rapid 

(greater than 3 m/s)-debris avalanche, to very rapid 

(0.3 m/s)-debris flow, to rapid (0.3 m/min) to very slow 

(1.5 m/yr)-earth flow, to extremely slow (0.06 m/yr)-

soil creep. Flows consist of moving material that resembles 

a viscous fluid. Soil creep (fig. 2C) is the extremely slow 

downslope movement of soil and rock material that takes 

place on many slopes where ground breakage is scant or 

absent. Accelerated creep may precede sliding. 

Many slope movements in the area are complex in that 

features of two or more basic slope movements are represented. What starts out as rotational-type sliding (slumping) 

can develop into a translational (or planar) movement which 

becomes a flowage feature in the lower part (fig. 2B). Not 

only are sliding and flowage combined, but the sliding itself 

consists of rotational and planar movements. Earth flows in 

cohesive materials can be considered complex because shear 

takes place along the flanks and basal surface (note slickensides on fig. 2D), and plastic flow may be indicated by the 

distribution of velocities within the displaced material 

(Varnes, 1978). 

GEOLOGY AND ITS RELATION TO SLOPE 

MOVEMENTS 

The Marietta area lies along the southwestern side of 

the Dunkard basin. Repetitive sequences of subhorizontal 

red shale and mudstone interbedded with occasional thin to 

thick sandstone and siltstone beds of Pennsylvania and Permian age underlie the Marietta area. Limestone, coal, and 

claystone are minor lithologies. The bedrock dips to the 

south at less than 1 o. 

Most of the bedrock belongs to the Dunkard Group, 

which includes the Waynesburg, Washington, and Greene 

Formations in areas to the northeast. Because of the absence 

of mappable Waynesburg coal at the base of the Waynesburg Formation in the Marietta area, a definable boundary 

for the base of the Dunkard Group could not be delineated 

(Collins and Smith, 1977, p. 15). The approximately 35-m 

section usually mapped as Dunkard is included by Collins 

and Smith (1977) in the underlying Monongahela Group. 

The Washington coal (at the base of the Washington Formation) is shown on their map as the base of the Permian. 

Differentiation of the Dunkard Group above the Washington 

coal into the Washington and Greene Formations was not 

possible at the scale of their mapping (1:62,500). 

In many parts of the Appalachian Plateau, soils 

(table 1) and weathered rock from certain parts of the stratigraphic section are responsible for a large number of slides 

in certain intervals (Pomeroy, 1978, 1979, 1982a, b). In the 

Marietta area, however, the distribution of slope movements 

is relatively uniform throughout the Monongahela and 

Dunkard Groups. This characteristic is related to the widespread occurrence of incompetent rock (mudstone, shale) 

interbedded with competent rock (sandstone, siltstone) 

(fig. 3). The widespread presence of the silty to clayey 

regolith and underlying incompetent rock is apparent in 

table 2. 

Rapid facies changes commonly occur within short 

distances, as revealed mainly by subsurface data (Collins 

and Smith, 1977), not only in this area but in other parts of 

the Dunkard basin as well (Pomeroy, 1986). I have found 

that individual lithologies (except for some coals that serve 

as marker beds) are seldom traceable for distances greater 

than 2.0 kilometers (km) throughout the Dunkard basin. 

Collins and Smith (1977, p. 11) referred to the "nonlayercake" nature of the surface rocks that gives rise to correlation problems. Figure 3 shows the lack of continuity in the 

units when stratigraphic sections at comparable elevations 

are compared. 

In many areas, outcrop distribution can be predicted. 

On the southwest-facing slopes, 1- to 2-m-thick sandstone 

4 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
Figure 2. Features of slope movements. 

A 

Basal shear surface 

Figure 2A. Idealized earth flows. Left, Surface features. Right, Subsurface features. From Keefer and Johnson (1983). 

ledges are common, and colluvial cover is generally thin. 

Colluvial cover usually is thicker along the northeast-facing 

slopes and commonly masks the sandstone ledges. 

Slope failures were noted within colluvium and at the 

colluvium-bedrock interface. Undoubtedly, subsurface investigations would reveal that some shear planes also occur 

within weathered bedrock (Pomeroy, 19 86). Observations indicate that most slope movements originate at or near 

weathered clay-rich bedrock. 

Subsurface observations of colluvium from trenches 

(Hooper, 1969a, b; S. F. Obermeier, U.S. Geological Survey, written commun., 1983) and auger borings (Sharpe and 

Dosch, 1942) along slopes in eastern and southeastern Ohio 

show that the weaker lithologic rock types, instead of extending horizontally to intersect the slope surface, thin 

abruptly and bend downslope (fig. 2C). Impervious materials (shale, mudstone, claystone) are stretched out roughly 

parallel to the slope and retard the downward percolation of 

surface and ground water. In this type of situation, a temporary perched water table (Campbell, 1975) may form during 

long periods of precipitation or during short periods of intense downpours if infiltration at the surface takes place at 

a greater rate than deep percolation. The saturated colluvium then becomes vulnerable to some form of disruption, 

such as earth flow movement. 

Colluvial thickness is variable on slopes, and, generally, colluvial deposits are thicker in the lower parts of 

slopes. Unfortunately, subsurface information is lacking except for Ohio Department of Transportation data along Interstate 77, where thicknesses from 1.5 to 5.4 m are indicated (table 2). Because shale and mudstone commonly 

predominate in the section, the weathering products are 

usually silty clays or clayey silts. 

Colluvium in the Marietta area may have been generated during the Pleistocene under different climatic conditions. The Wisconsinan glacial boundary lies about 64 km 

northwest of the Marietta area. Sand and gravel are found in 

the Ohio and Muskingum River valleys. Remnants of lake 

silts and clays are found along Duck Creek and the Little 

Muskingum River. Any discussion of the Pleistocene climate south of the glacial border is subject to considerable 

speculation and debate. However, Bums (1958) believed 

that the climate in southen Ohio was cool and moist during 

the Wisconsinan glaciation. The Pleistocene climate in the 

Geology and Its Relation to Slope Movements 5 
8 

c 

'----v----' 

Zone of 

colluvium 

Figure 28. Complex slope movement. 

Claystone 

Figure 2C Soil creep as a prelude to landsliding. Modified from Sharpe and Dosch (1942). 

nonglaciated Appalachian Plateau region of Pennsylvania, 

West Virginia, and Ohio is believed to have been conducive 

to increased weathering resulting in the development of 

colluvium and slope movements and the masking of bedrock 

(Gray and others, 1979). Radiocarbon dating of slide planes 

at construction sites along major drainages in West Virginia 

indicate a minimum age of 40,000 years (yr) at Weirton 

(D'Appolonia and others, 1967) and about 8,940 and 

9, 750 yr at Morgantown and Wheeling, respectively 

(Philbrick, 1962). 

Study of geologic controls on where slope movements 

occur in the Marietta area is hampered by poor exposures, 

thinness of lithologic units, and rapid facies changes within 

short distances. 

CLAY MINERALOGY 

Twenty-two clay samples were collected from several 

parts of recent earth flows, including basal shear surfaces as 

well as from a few areas unrelated to any slope failure. 

Despite the varied collecting points, the samples contain 

similar suites of clay minerals. The X-ray diffraction study 

showed that the dominant suite contains illite, kaolinite, and 

6 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
Figure 20. Slickensided basal shear surface (A) of a fresh earth flow. 

a clay component that may be vermiculite; the other suite 

contains illite, kaolinite, and a more smectite-type expandable clay (Virginia Gonzalez, U.S. Geological Survey, written commun., 1983). No clear difference in clay mineralogy 

exists between the basal shear surfaces and the material 

elsewhere in the landslide deposit or in adjacent soils. The 

illite is potassium deficient (Gloria Hunsberger, U.S. Geological Survey, written commun., 1983), which is a condition prevalent elsewhere in unstable shales and mudstone of 

Devonian to Permian age in western Pennsylvania. For 

southeastern Ohio, Fisher and others (1968, p. 79) concluded that "simultaneous deposition of ferric iron with degraded illitic clay prevented reabsorption of the bonding 

potassium ion in the depositional environment. The continued presence of iron has greatly inhibited the reconstitution 

of the clay throughout diagenesis and late geologic time." 

They indicated that degraded illites swell in the presence of 

water similar to montmorillonite, except that expandability 

is not as great. 

METHODOLOGY 

Expectations were that a better understanding of slope 

processes could be achieved simultaneously with production 

of a detailed inventory map (U.S. Geological Survey, 1982, 

p. 24). Field data were obtained for areas shown in figure 1B 

over a period of approximately 75 to 80 days (d) along a 

series of closely spaced traverses. Black and white aerial 

photographs from 1943 to 1981 proved useful for comparison studies (table 3). 

The features mapped as recently active landslides in 

figures 4, 6, 10, 16, 19, 23, 27, and 28 show a main scarp 

and toe (fig. 2A ). The most prevalent type is an earth flow 

(fig. 2A ); other types include slumps, debris slides, and 

complex forms, which show characteristics of slumps and 

earth flows (fig. 2B ). In addition to discrete lobate landslides, the landslide designation also includes areas of coalescing slope movements. 

The main scarp and toe commonly measure from 0.5 

to 1. 5 m in height. The surface of the landslide is hummocky and generally cracked, shows tilted trees, and may 

have small areas of standing water. Springs may develop in 

the head areas of the landslides or above and also may 

develop at the frontal margin of the toe. A slickensided basal 

shear surface is common in the head area and still may be 

evident in fresh landslides (fig. 2D ). The material involved 

in the movement is sliding on these striated (slickensided), 

clayey surfaces. Subsurface investigations by means of 

backhoe trenching elsewhere in the Appalachian Plateau 

Clay Mineralogy 7 
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Table 1. Slope-failure-prone soils, estimates of soil properties, and engineering interpretations, Marietta area 

[Based on Lessig and others (1977)] 

Suitability as 

Available source of roadfill; 

Soil Parent material Percentage Classification Shrink-swell soil features 

Soil series mapping of area Permeabi I ity water affecting highway 

unit (approximate) (AASH0) 1 potential (moisture) location, ponds capacity excavations for 

dwellings 

Upshur---------- Gilpin-Summitville-Upshur Red shale (mudstone) >50 A-72 Moderate to Slow2 --- Moderate2 - - - Poor; unstable 

complex; Upshur silty clay residual to collu- high. 2 clayey material 

loam; Upshur associated vial. subject to 

very stony; Upshur-Gilpin slippage. 

complex; Upshur clay. 

Vandalia - - - - - - - - Vandalia silty clay loam---- Colluvium (mudstone <5 A-6, A-7 Moderate to Slow ---- - --- do ---- Do. 

and red clay), thick high. 

deposits on foot 

slopes. 

Hayter-Vandalia - - Hayter-Vandalia channery Colluvium (shale, <2 A-4, A-6, Low to high Variable-- - --- do ---- Fair to poor; conloams and stony complex. mudstone, red A-7 siderable unclays, and coarse stable material 

textures). subject to slippage. 

Belpre - - - - - - -- - - Belpre clay - -- - - -- - - - - - - - Calcareous shale, <1 A-7 High------- Slow ---- ---- do ---- Poor; unstable 

mudstone, residual clayey material, 

to colluvial. subject to slippage. 

Brookside ------- Brookside silty clay loam - -- Colluvium, thick de- <1 A-6, A-7 Moderate - - - Moderately High- - - - - - - - Do. 

posits on foot slow. 

slopes. 

1 American Association of State Highway Officials system. A soil is classified in one of seven groups ranging from A-1 through A-7 on basis of grain-size distribution, liquid limit, and plasticity 

index. A-7 soils are clayey, have low strength when wet, and are the poorest soils for subgrade (Lessig and others, 1977; p. 62). 

2Applies to Upshur part of complexes. 
950 

900 

850 

800 fw 

w 

LL 

~ 

z· 

0 

I= 

< > 

w 750 ...J 

w 

700 

650 

2(o) 

3(p) 

s 

1(o) 

M 

EXPLANATION 

llJJilll Concealed interval 

4(0) 

M 

ss 

M 

s 

M 

(probably mostly mudstone/shale) 

ss Sandstone 

s Shale 

M Mudstone (clay shale) 

MS Mudstone/ shale undifferentiated 

L Limestone 

(o) Data from Ohio Geological Survey files 

(p) Data from current investigation 

NOTE: Early investigators did not differentiate 

shale and mudstone (see section 12) 

s 7(o) 

6(o) 

5b(p) 5c(p) 

ss ss 

M 

MS s 

s 

5a(p) 

s s s 

M 

M 

ss 

1 Russet Run ((}-15320) 

2 Devol Run ((}-15321) 

3 Devol Run (lower end) 

4 March Run ((}-9585) 

5 Ridge east of Devol a 

6 Stanleyville area ((}-8111) 

7 Brush Run tributary ((}-8110) 

8 Ohio 26 East ((}-6672) 

9 Hadley Run ((}-8254) 

10 Area north of Ohio 7 

11 Dodge Run ((}-8273) 

12 Harmar ((}-10319) 

Figure 3. Lithologic sections, Marietta area, Ohio. See figure 1 8 for locations. 

(S. F. Obermeier, U.S. Geological Survey, written commun., 1983) indicate the presence of multiple shear planes 

within any particular earth flow. 

Movements of less than 10 m in maximum dimension 

are not shown on the maps. The slope failure designation 

does not include rockfall or soil creep; the latter is prevalent 

on all slopes in the Marietta area. 

At each site, I recorded the type of movement, approximate dimensions, orientation, vegetation, elevation of 

head and toe, configuration of and position on slope, angle 

of adjacent slope, character 9f material in the main body, 

proximity of bedrock, influence of slope modification (if 

any), surface drainage, and presence of seeps. At a small 

number of fresh landslide sites, the distance and angle of the 

basal shear plane to the surface could be measured. 

Two U.S. Geological Survey open-file maps 

(Pomeroy, 1984b, 1985) were prepared from these data and 

are available as supplementary material to this text. The first 

Methodology 9 
map is a detailed inventory map of recently active slope Area West of Muskingum River 

failures, and the second is a map of relative slope stability. 

North of Ohio 676 

REGIONAL DESCRIPTION OF SLOPE (Figure 4) 

MOVEMENTS Examination of the lower slopes below the 700-foot 

(ft) contour along Devol and Russet Runs reveals scant slope 

Figures 4, 6, 10, 16, 19, 23, 27, and 28 show recently movement activity. Lithologic data indicate that sandstone 

active landslides. Each map figure is outlined on figure lB. makes up 50 to 60 percent of the section. 

Complete data are presented in the Appendix, and only However, an extremely unstable interval of mostly 

selected localities are described in the following text. mudstone and shale lies between 800- and 890-ft elevation 

Table 2. Summary of selected soil test data and character of underlying bedrock along Interstate 77 (fig. 18) 

[From Ohio Department of Transportation, District 1 0] 

Approximate Thickness Depth Coarse Fine Percent Location elevation, interval, to sand, sand, Silt, Clay, Liquid Plasticity AASHO 

No. bedrock, Aggregate, limit index H20 rating* in feet in feet in percent in in In tn content in feet percent percent percent percent 

135 790 0.5- 3.0 0 0 2 28 70 47 28 16 A-6, 7 

3.0- 7.5 0 1 14 50 35 25 7 8 A-4 

7.5- 9.0 9.0 27 2 3 40 28 30 11 7 A- 6 

781-772 { 9.0-15 .0 red weathered indurated clay 7 

15.0-18 .0 light-gray weathered indurated clay 3 

772-763 { 18.0-23 .0 broken red shale 6 

23.0-27.0 - - - - - - - - - - do --------- 9 

152 790 0.2- 3.0 0 3 6 52 39 33 11 17 A-6 

3.0- 5.0 5.0 45 2 5 23 25 34 11 24 A- 6 

785-781 5.0- 9.0 brown weathered sandstone 

[ 9.0-14.0 red weathered indurated clay 13 

781-760 14.0-19.0 - - - - - - - - - - do --- ------ 11 

19.0- 25.0 - - - - - - - - - - do ----- - --- 9 

25 .0- 30.0 - - - - - - - - - - do -------- - 9 

191 780 0.5- 5.0 0 2 6 38 54 40 14 16 A- 6 

5.0-10.0 10.0 0 39 59 34 12 13 A-6 

r0.0-15.0 weathered indurated clay 

770-755 15.0-20.0 - - - - - - - - - - do --------- 20.0-25.0 - - - - - - - - - - do ---------

218 640 0.2- 5.0 0 4 40 55 48 23 22 A- 6, 7 

5.0- 8.0 0 0 46 53 44 22 27 A- 6, 7 

8.0-12.0 0 1 10 47 42 35 16 25 A- 6 

12.0-15.0 47 2 24 12 15 22 2 14 A- 2- 4 

15.0-17.0 17 2 7 33 41 36 13 17 A-6 

17.0-18.0 18.0 0 5 6 18 71 47 18 19 A- 6, 7 

622-620 18.0-20.0 black coal blossom 

620-617 20.0-23.0 broken gray sandstone 

308 860 0.0- 3.0 0 3 6 35 56 40 17 14 A- 6 

3.0- 8.0 25 1 27 46 37 14 13 A-6 

8.0- 11.0 4 0 1 34 61 36 14 10 A- 6 

11.0-16.5 13 2 6 35 44 32 11 10 A- 6 

16.5-18.0 18.0 24 2 36 37 35 12 16 A-6 

18.0-21.0 red, brown, and gray weathered indurated clay 

21.0-24.0 gray weathered shale 

842-829 24.0- 26.0 brown and gray weathered shale 

26.0-29.0 red weathered indurated clay 

29.0-31.0 broken brown silty shale I (' 

,\' 

*See table I; footnote I. 

10 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
Table 3. Aerial photographs used in investigation 

Year Scale Flight seriesPhotograph numbers Source of negatives 

1943 (6/23) 1:20,000 CMD-2A-74 to 84 

2A-88 to 95 

3A-26 to 28 

3A-42 to 51 

3A-62 to 66 

U.S. Department of Agriculture 

Do. 

Do. 

Do. 

Do. 

1956 (3/20-21) I 

1958 ( 4/8) 

1968 (5/7) 

1:31,000 

1:28,000 

1:18,000 

FGS-CCD-2-23 to 27 

BGS-CCD-3-2 to 7 

3-56 to 61 

VSW 1-3 to 9 

U.S. Geological Survey 

Do. 

Do. 

Do . 

Do. 

Do . 

Do. 

Do . 

Do. 

Do. 

Do. 

Do. 

VBXD 1-35 to 45 

1-53 to 62 

1-67 to 76 

2-5 to 14 

2-18 to 26 

2-133 to 143 

1975 (5/2) 

1976 (3/22) 

1980 ( 1 0/30) 

1:78,000 

1:24,000 

VOLT 5-133 to 136 

VOLT 7-26 to 29 

RSU 188-191 Ohio Department of Natural Resources 

RSU 218-224 Do. 

RSU 239-245 Do. 

RSU 267-276 Do. 

RSU 281-284 Do. 

1981 (6111) RSU 45-48 

RSU 80-85 

1

0blique (cannot be viewed stereoscopically). 

south of both drainages with head scarps of most earth flows 

occurring between 870 and 890 ft (locality A). Drainage 

channel heads begin from about 5.0 to 6.0 m downslope 

from the toe of a few earth flows; in general, a surface 

drainage network does not exist along that part of the slope 

covered by recent movements. 

The southwest-facing forested slope (locality B) of 

the unnamed drainage to the south of Russet Run is devoid 

of any recent failures and has well-defined surface drainage 

channels. The slope is better drained and less hummocky 

and supports a much less varied vegetative cover than part 

of the opposing north-facing slope (to the southwest), which 

shows several recent earth flows. Slopes with closely spaced 

drainage channels are inferred to be well drained. 

The unstable forested slopes south of Russet and 

Devol Runs have wide areas of contour concavity (hollowed 

out) that represent areas of coalescing older (prehistoric) 

failures. Such areas exhibit only slight development of surface drainage channels. Earth flows in this area have developed without any slope modification by man. 

Slopes bordering Indian Run and its tributaries generally show many failures. The most severely affected slope 

is a northeast- to north-facing slope (locality H) with a 

nearly continuous 1.3-km-long zone of scarps, disoriented 

trees, and ponding. Although slumping is locally prominent, most of the movements are shallow planar earth flows. 

Do. 

Do. 

A marked decrease of slope movements is apparent on the 

opposing southwest-facing slope in addition to the mostly 

well-drained, southwest-facing slope on the other side of the 

ridge road. Most of the failures along Indian Run are natural 

earth flows and complex movements involving some slumping. Slopes adjacent to head areas of these movements range 

from 13° (22 percent) to 27° (55 percent). A sandstone ledge 

at about the 800-ft contour lies above a poorly exposed, 

dominantly red mudstone-shale slope and is the upper limit 

to a well-defined zone of intense slope movement on the 

southern side of Indian Run. 

A major failure above Leland and Gilman Streets 

(locality J; fig. 5) damaged three houses, which were later 

razed. Most of the colluvial material has been removed from 

an area where movement had accelerated in March 1976. 

Costs arising from repurchase of the condemned properties 

and remedial work exceeded $350,000. The movement apparently developed after Gilman Street was widened 

(fig. 5). Slow movement (mostly creep) is continuing in the 

lower part of the area and still is affecting sections of Leland 

and Gilman Streets, as well as the railroad track ballast. The 

lower slope has a subtle hummocky surface of low relief. 

The problem is compounded by a movement of watersaturated fill from under the road into the Muskingham 

River, resulting in some subsidence of Gilman Street 

(Robert Badger, Marietta Times, September 20, 1980). Efforts to intercept the drainage continued in 1984. 

Regional Description of Slope Movements 11 
CONTOUR INTERVAL 20 FEET 

0 

0 1 KILOMETER 

Figure 4. Area north of Ohio 676. 

12 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 

EXPLANATION 

• Recently active slope failure 

A Movement described in text 

Boundary of map area 
Figure 5. Site of the slope failure above Gilman Street (fig. 4, locality J). Shown are the base of the sandstone ledge (A), Leland 

Street (B), the railroad track (C), and Gilman Street (note "Bump" sign) (0). 

Two debris avalanches (locality K) southeast of locality 1 are discernible from the eastern bank of the 

Muskingum River. The northern debris avalanche originates 

from an approximately 20-m-wide, crescent- shaped wet 

area below three houses and extends to the railroad tracks. 

The wetness is caused by a drain pipe that leads into the 

southern side of the cove from one of the houses. The head 

scarp of a younger debris avalanche to the south is hidden 

by high brush below the front of a backyard porch. The floor 

of the head area is wet, suggesting seepage. 

South of Ohio 676 

(Figure 6) 

The slope above Ohio 7 at Harmar and its continuation to the southwest has stability problems of various types. 

An essentially continuous zone of creep and coalescing 

earth flows extends laterally for about 1 km. The area involving Lancaster Street (locality A) has been particularly 

troublesome. Nearly 240 m of piling installed across an 

approximately 18-m-wide area cost the city $16,000 (Robert 

Badger, Marietta Times, September 2, 1980), but that 

amount did not include the curbing, gutter, and drainage 

renovation. Movement also is occurring along the lower 

slope about 30 m downhill along Lancaster Street opposite 

Douglas Street, where steel beams support a suspended 

sidewalk. Slow movement continued at both Lancaster 

Street locations in spring 1984. 

Slow earth flow movements and creep are widespread 

along the same slope to the south adjacent to other streets 

that cut diagonally across the slope (locality B). Old steel 

and concrete walls (some with vertical steel beams, along 

with more recent steel cribbing), barely discernible 0.3-mhigh earth flow toes, occasional ground cracks, and a conspicuous hummocky appearance of the lower slope attest to 

historic activity taking place downslope from a 7.5- to 9.0-

m-thick sandstone. 

A rockfall hazard lies above Ohio 7 to the southwest 

(locality C). When the highway was constructed in 1940, 

considerable excavation was necessary to provide adequate 

width for increased traffic. Two large rockfalls occurred in 

the 1940's, and another, on January 31, 1950. The latter 

rockfall is pictured in the Ohio State University Engineering 

Experiment Station News (Ohio State University, 1950) 

along a 3.0- to 4.5-m-thick mudstone and minor shale slope 

overlain by 9.0 to 11.0 m of thick-bedded sandstone (fig. 7). 

Separation along nearly vertical joints in the sandstone and 

rapid weathering of the underlying mudstone continues to 

cause additional rockfalls. 

Regional Description of Slope Movements 13 
At locality D, recent movements have disrupted an 

older macadam surfaced road that was built largely on red 

mudstone-shale fill between the highway and the river as 

shown on photomaps (Lessig and others, 1977). Slippage 

originated beneath a 9-m-thick sandstone ledge below 

Ohio 7 and above the railroad tracks. The composition of the 

fill and the possible rerouting of drainage from the highway 

39° 

22' 

30' 

Figure 6. Area south of Ohio 676. 

above are probable factors in the severe surface disruptions 

throughout this area. 

A rapid debris slide (locality G; fig. 8) took place 

along the steep slope opposite the slump-earth flow (locality 

F) in early May 1983 during an extremely wet period. 

A strong lithologic control on the slope movements is 

demonstrated in the vicinity of Pinehurst. The earth flows 

-

A 

EXPLANATION 

Recently active slope failure 

Movement described in text 

Boundary of map area 

1 MILE 

1 KILOMETER 

CONTOUR INTERVAL 20 FEET 

14 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
Figure 7. Rockfall area along Ohio 7 (fig. 6, locality C) to the southwest of Marietta. Shown are the lower part of a major 

sandstone bed (A) and mudstone with some shale (B). 

and the slump-earth flows along a northwest- to east-facing 

slope to the south of Pinehurst (locality H) have head scarps 

at elevations of from 810 to 830 ft. On the northern side of 

Ohio 550, three movements (locality 1), dating from pre1980, April1982, and post-late April1983, took place at an 

altitude of 770 ft below a 7 .5-m-thick sandstone. Furthermore, unstable slopes to the northwest and west of Moore 

Junction (fig. 9) occur in the regolith derived from largely 

shale and mudstone below a sandstone ledge. 

Area Between Muskingum River and Duck Creek 

West of Interstate 77 

North of Ohio 821 

(Figure 10) 

A massive, 350-m-wide earth flow in fill and the 

subjacent slope (locality A) took place before May 1968 

during or after the Interstate 77 construction (fig. 11). Red 

shale-mudstone fill from the highway cut to the east had 

been added to the northwest-facing slope. No documentation was available as to the approximate timing and rate of 

movement. The May 1968 aerial photographs show a 

damming of the drainage because of the slope movement. A 

smaller, 100-m-wide earth flow (locality B), 0.7 km to the 

north, had not shown failure before May 1968 but shows 

movement on the 1980 aerial photographs. 

Two different environments for slope failures have 

occurred along the hillsides to the north of Devola. Composed largely of fill, the backyards of six houses failed in the 

early part of 1979 on the eastern side of Strecker Way 

(locality E). Renovation of the 160-m-wide slope took place 

in spring 1979 (Robert Jones, Soil Conservation Service, 

oral commun., 1983) resulting in a reduction of gradient. 

The overextension of fill for the backyards and its surcharging of the subjacent slope probably accounted for the resulting instability. 

Houses have been built along a natural slope to the 

east of locality Eon the eastern side of Sylvan Way (locality 

F). The use of fill has been minimal in backyard areas in 

contrast to the Strecker Lane locality. The head scarp of one 

earth flow is only 1 m from the foundation of one house. The 

rear porch sloped downhill in April 1983 (fig. 12). Other 

earth flows in the immediate. vicinity include a 24-m-wide 

hollowed-out slope with one large beech tree near the base 

of the movement, a smaller earth flow below the backyard 

of the house adjacent to that shown in figure 12, and a 

Regional Description of Slope Movements 15 
Figure 8. Debris slide along Ohio 550 (fig. 6, locality G) during the early May 1983 wet period. Shown is the seep at the base 

of the sandstone (A). 

Figure 9. Earth flow 2 km northwest of Moore junction. 

Shown are the base of the sandstone ledge (A), seepages common at contact with impermeable mudstone-shale, and an 

earth flow immediately below contact. 

vacant lot earth flow. The earth flows head at slightly above 

or below 700 to 710 ft. 

The western side of the forested highland to the east 

of Ohio 60 shows many slope movements. A 340-m-wide 

failure (locality G) extending in elevation from as high as 

850 ft to as low as 620 ft lies mainly to the south of the ruins 

of a large house built in 1968 (fig. 13). Slope modification 

in the immediate vicinity of the house probably triggered 

movement locally but is not believed to have had any influence on the larger part of the movement to the south. The 

movement probably is classified best as an earth slump, but 

a deeper seated rock slump cannot be ruled out. Tilted 

sections with small ponds in the head area plus an obvious 

backward dip of the basement and first floor of the house 

(fig. 13) suggest a slide deeper than the usual shallow planar 

earth flow of the area. 

According to information given Marilyn Ortt 

(Marietta botanist, written commun., 1984 ), the house was 

built in 1968. Slippage first occurred during spring 1975. 

The contractor did extensive renovation, including reinforcement of the rear concrete block wall, in December 

1975. Trees and soil were removed from behind the house 

after recommendations by "authorities." A local real estate 

salesman took a 1-yr option to buy and moved in at the 

beginning of 1979 or 1980. No apparent movement had 

occurred during the interval that had elapsed since the 

"repair work." During an especially wet spring in 1979 or 

1980, the occupant noticed that a drainpipe parallel to the 

basement wall jutted into a room within the period of 1 d. 

The house was abandoned after the occupant confirmed his 

16 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
0 

0 

• Recently active slope failure 

A Movement described in text 

1 KILOMETER 

CONTOUR INTERVAL 20 FEET 

Figure 10. Area north and west of Ohio 821 . 

Regional Description of Slope Movements 17 
Figure 11. Fill and subjacent slope failure along the western 

side of Interstate 77 (fig. 10, locality A). Shown are the toe of 

the 350-m-wide movement (A) and the edge of Interstate 77 

(B). 

Figure 12. Backyard failure in Devola (fig. 10, locality F) . 

Shown are the head scarp (A), the out-of-pl umb porch co lumn 

(B), and the lateral margin of the earth flow (C) . 

Figure 13. Ruins of a large house at the northern end of a 

340-m-wide slope failure (fig. 10, locality G) to the east of 

Devol a. 

suspicions that the house was shifting by checking the floor 

with a level. The house was dismantled in either 1981 or 

1982 after continued movements precluded habitation. 

The events described above can be correlated with the 

rainfall record at Marietta (fig. 14). The house was built at 

the end of a drier than nom1al period. Above normal rainfall 

for most of the period 1970 to 1975 saw a buildup of groundwater levels in a monitored well (U.S. Geological Survey, 

1965-77). Pore-water pressures at the house site probably 

also increased. Renovation of the slope behind the house 

plus a couple of slightly below normal rainfall years ( 1976-

77) probably relieved the rate of slope movement temporarily. Resumption of noticeable movement in 1979 or 1980 

correlates with the probable high pore-water pressures 

caused by above normal rainfall in 1979 and 1980. Examination of late-1980 aerial photographs shows that the areal 

extent of inclined and downed trees is almost as extensive as 

what one would expect to see on aerial photographs taken at 

the time of the 1983-84 investigation. In contrast, 1968 

aerial photographs do not indicate any major slope failure 

area. The freshness of the ground cracks and scarps along 

the slope attest to the very recent movements at locality G. 

A preferential siting for many earth flows is suggested 

in several locations other than those along the Muskingum 

River and Second Creek. Slope movements along 

northwest- to east-facing slopes to the east and northeast of 

locality G are more numerous than those along other slopes. 

In general, well-defined drainage channels are dominant 

along southwest-facing slopes. Surface drainage development is more pronounced along these slopes than along 

north- and east-facing slopes. Natural channels spaced about 

every 30 to 60 m across the slope (fig . 15) seem to be 

sufficient to drain hillside slopes and prevent high porewater pressure buildup in soil and colluvium. Consequently, 

these southwest-facing slopes show few movements. 

South of Ohio 821 

(Figure 16) 

A dense pattern of slope failures occurs in the highland area south of Colegate Road and north of the central 

part of Marietta. One of the better known movements (locality A) took place behind the Army Reserve Center and 

involved the parking area. This 80- to 90-m-wide slumpearth flow took place in fill and subjacent slope after May 

1968. The 1968 aerial photographs show some flowage of 

earth material in the lower extremities of the fill emplacement, but the parking area was intact at that time. The head 

area on the western side of the slump-earth flow had retrogressed to the foundation wall of the garage in April 1984, 

but that structure still was sound without any foundation 

cracks. 

Development of the northwest-facing slope to the 

southeast of Muskingum Drive (Ohio 60) has been threatened by earthflows and creep (locality B). One earth flow 

18 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
has caused extensive property damage despite remedial 

measures (fig. 17). 

Several landslide areas became well known to 

Marietta residents in 1980 following greater than normal 

rainfall during the spring and summer of that year (Marietta 

Times, selected issues, 1980). A small slope movement is 

reported to have caused the main water line to Memorial 

(jj 

0:: 

UJ 

1-

UJ 

~ 

50 

(127) 

45 

(114) 

~ 40 

~ (102) 

(f) 

~MEAN* 

u 

z 

~ 

z' 

0 

~ a: 

u 

w 

0:: 

a.. 

67 68 69 

*Mean (average I rainfall at Marietta is 38.62 inches 

(98.09 centimetersl for 63 years of record. Figure is 

based on data provided by John Hughes (National 

Oceanic and Atmospheric Administration, Asheville, 

N.C., oral commun., 19861 

Figure 14. Rainfall at Marietta, 1962-83. 

70 71 

Hospital to break along Strecker Hill (street) (locality C). A 

water line under Ray Street (locality D) broke twice in 3 d 

because of a slow earth flow that threatened several houses; 

two houses on Ray Street showed collapsed foundations 

during this investigation. The hillside below Ray Street is 

part of an ancient failure nearly 100m wide. Other failures, 

including Cullen A venue (locality E), documented as mov72 73 

YEAR 

74 75 

Regional Description of Slope Movements 19 
Figure 15. Slope drainage channels prevalent along the 

southwest-facing slopes. Shown are the drainages (A) along 

the slope lacking in recent failures. 

ing slowly in 1980 (Marietta Times), appeared active in 

1983. 

The Walnut Hills Drive slope failure (locality F), 

probably the best-known slope movement in Marietta, lies 

below Grandview A venue and is part of a prehistoric(?) 

failure that extends to the railroad tracks below Greene 

Street. The hummocky head area is downslope from a thickbedded sandstone that underlies Grandview Avenue. 

Springs at the base of the sandstone contribute to a wet 

slope. The 350-m-wide, very slow movement has sealed off 

Walnut Hills Drive, which cuts diagonally across the affected slope. The city officially closed Walnut Hills Drive 

on August 29, 1972, because of the slow continual damaging earth flow accompanied by some slumping in the head 

area. The macadam surface of the closed Walnut Hills Drive 

has been overgrown by vegetation and is cracked locally 

(fig. 18). The few houses along the Drive, as well as a larger 

number along the northern side of Greene Street, have been 

removed. A total of approximately 18 houses has been razed 

within this large earth flow [approximately 54,000 square 

meters (m2)]. 

The appearance of the slope on aerial photographs 

during the 25-yr span between the 1943 and the 1968 flights 

reveals no significant differences. However, a major change 

in land use is apparent (with the removal of houses) when 

comparing 1968 with 1980 aerial photographs. The effect of 

a wetter climate during the decade of the 1970's probably is 

the major contributing factor in the slow, but destructive, 

earth movement. 

Houses on the southern side of Greene Street show 

foundation cracks and some slightly out-of-plumb frames. 

Only one house on the northern side of Greene Street, just 

west of the Phillips Street intersection, still is standing. The 

eastern side of the upper part of the movement shows retaining walls of various ages that have moved downslope. Yellow clay was found nearly 7 m below the surface at the toe, 

according to records kept by the City Engineer. Whether or 

not this clay served as the sliding plane is conjectural. Seepage from the slope above Greene Street has caused hazardous icy conditions on the road during the winter. Small 

sections of the lower western end of the movement occasionally have moved out into Greene Street during wet 

periods. 

East of Interstate 77 

(Figure 19) 

The major areas of slope movement in this region are 

the northeast- and east-facing hillsides facing Duck Creek. 

The mostly northeast-facing slope opposite of Stanleyville 

and extending northwestward along a tributary drainage 

shows a high density of mostly earth flows (frontispiece; 

fig. 19). Slumps and slump-earth flows are only locally 

common. 

Figure 20 shows two earth flows (locality A) on the 

property of Frank Vaught, which is opposite of Stanleyville. 

These earth flows are obvious on the 1980 aerial photographs but cannot be seen on the 1968 aerial photographs. 

The property owner believed that the removal of locust trees 

in the head areas might have been a factor in the initiation 

of the earth flows. Slumping is absent from the head areas 

of both earth flows. The movements are strictly planar with 

up to 1 m of earth material removed from the head area. 

Both earth flows show renewed activity in the form of transverse cracks at the edge of the 760-ft bench. An older earth 

flow (locality B; fig. 20) lies adjacent to the easternmost 

earth flow. To the northwest, other earth flows (localities B, 

C; figs. 21, 22) are typical grassland and woodland slope 

movements. 

Area Between Duck Creek and Little Muskingum 

River 

North of Ohio 26 

(Figure 23) 

Much of the slope movement activity begins at about 

the 700-ft contour from the Stanleyville area southward 

along Duck Creek to Ohio 26. 

Earth flow (planar) movement, whether in forest or 

grassland, is the most common type of slope failure (localities A, B; figs. 24, 25). Earth slumps along creeks such as 

one along Brush Run (locality C; fig. 26), are rarely large 

enough to show on a 1:24,000-scale map. Unmapped 

smaller slumps along Duck Creek imply that the base of the 

movements is below the creekbed. 

A 400-m-wide area of a slow-moving regolith lies 

north of Lynch Church on the Duckworth farm (locality D). 

The owner reported that the slope surface now occupied by 

a massive earth flow was smooth during the early 1960's. 

Replaced telephone poles across the area are leaning, and 

the pond is being threatened by the moving hummocky 

mass. Because no manmade modification of the slope has 

been made since 1964, the high ground-water level brought 

20 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
0 1 KILOMETER 

CONTOUR INTERVAL 20 FEET 

Figure 16. Area south of Ohio 821 . 

Regional Description of Slope Movements 21 
Figure 17. Crib failure behind the motel to the east of Ohio 60 (fig. 16, locality B). Shown is the toe of the earth flow 

that pushed in an exterior wall (A) and the cribbing that moved downslope and almost touched the structure (B). 

Figure 18. Walnut Hills Drive slope movement (fig. 16, locality F). Shown is one of the many scarps in the upper areas of the 

350-m-wide movement (A). Macadam surface is a vestige of 

Walnut Hills Drive. 

on by the above normal rainfall from 1970 to 1983 is probably the triggering mechanism. 

A traverse along Brush Run reveals a complete lack of 

recent movements along the west- to southwest-facing 

slope. Thin sandstone ledges can be discerned at various 

elevations along this slope with thin colluvium covering 

intervals between the ledges. In contrast, the opposing eastto northeast-facing slope has many earth flows, extensive 

colluvial cover, and hummocky ground. 

Burchs Run, Negro Run, and several small northsouth drainages to the east (locality F) show few slope 

movements. Sandstone outcrops are numerous along these 

slopes, which have networks of surface channels and lack 

ponds or wet areas. Section 7 (fig. 3), which occurs along 

the road eastward from Brush Run, indicates that about onehalf of the bedrock is sandstone without any shale-mudstone 

interval greater than 8 m. 

An abrupt increase in earth flows and complex movements southward to Ohio 26 (locality G) reflects a change in 

bedrock facies where mudstone and shale become more 

dominant. Few sandstone ledges were seen in this area. 

Section 8 (fig. 3), which is along Ohio 26, shows a significantly higher proportion of mudstone-shale to sandstone 

than does section 7. North- and northeast-facing slopes are 

the favored areas for the failures. 

South of Ohio 26 

(Figure 27) 

The highland area to the east of Duck Creek shows 

heads of recent slope movements in the vicinity of the 680-

22 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
1 KILOMETER 

CONTOUR INTERVAL 20 FEET 

Figure 19. Area east of Interstate 77 and west of Duck Creek. 

Regional Description of Slope Movements 23 
Figure 20. Earth flows opposite of Stanleyville (fig. 19, locality A). Shown are recently active earth flows (A1 and A2), the toe 

of an old earth flow (8), and the natural bench below the currently active part of earth flow A1 (C). 

and 800-ft contours. Most of the larger sized movements 

postdate the 1968 aerial photographs. The largest failure, an 

earth flow-slump (locality A), is a nearly 100-m-wide, relatively thin planar movement. A nearly 1.0-km-long segment 

of Duck Creek was rerouted sometime before 1956 to its 

present alignment along a more direct route against the 

slope . During high water, the lower slope probably is subject to increased pore-water pressure and resultant reduction 

in shear strength. Also, increased lateral erosion by Duck 

Creek probably has reduced the stability of the lowermost 

slopes by unloading support from the toe slope. 

A 140-m-wide zone includes two closely spaced, very 

recent movements mapped as one (locality B). One of the 

movements is traversed diagonally by an access road, 

whereas the other is bordered laterally by a pipeline. Slope 

modification that impeded the natural drainage probably 

caused the failures. Natural drainage channels border this 

area to the north and south where no recent slope movement 

exists. The presence of these drainage channels might account for the lack of slope movements in the adjacent area. 

Particularly significant is the well-drained cove north of 

locality B that shows no slope failures. 

Slopes bordering major drainages have a high failure 

density. A large, very irregular, 140-m-wide earth flow 

(locality D) with a 1.5-m-high head scarp lies behind a 

recently enlarged industrial building. Because the toe lies 

several tens of meters beyond the back lawn of the building, 

modification at the base of the slope did not cause the 

movement. The toe of a much smaller earth flow to the 

northwest, however, is only 1 m from the northwestern end 

of the building and probably was initiated by lower slope 

modification. A north-northwest-trending valley (locality E) 

to the north of Comerville has a southwest-facing slope with 

many first-order drainage channels and only a few small 

recent movements and a northeast-facing hummocky slope 

with numerous recent failures. 

Slopes in the vicinity of Hadley Run and the next 

drainage to the east show failures at various elevations. A 

predominance of shale-mudstone over sandstone with several moderately thick (more than 10-m) intervals of weaker 

rock accounts for a higher than average occurrence of landslides in this area. The nearly 100m of this section (section 

9; fig. 3) shows a ratio greater than 2 to 1 of shale-mudstone 

to sandstone. 

The 0.4-km-long northeast-facing slope along the 

northwest-trending creek (locality F) 1.5 km northeast of 

Hadley Run is hummocky but without any recent slope 

failures, whereas the 0.6-km-long southwest-facing slope 

24 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
Figure 21. Looking across the less than 100-m-wide earth flow (fig. 19, locality B). Shown are the lateral margins (A), the 

repaired pipeline aligned parallel to the direction of movement (B), and the ponded area (C) . 

Figure 22. Head area of earth flow to the east of Ohio 821 

(fig. 19, locality C). Shown are part of the north lateral margin 

(A), the basal shear su rface (B), and the clump of a displaced 

regolith (C). 

shows numerous recent movements. Examination of a 1.8-

m-thick sandstone and shale sequence in the creekbed shows 

no inclination indicating that structure cannot explain the 

selective occurrence of the failures. 

Area South of Little Muskingum River 

(Figure 28) 

The most intense area of landslides (mostly earth 

flows) anywhere in the Marietta area lies north of Ohio 7 

(and the Ohio River) and south of Coal Run. This forested 

area (4.5 km2) with 120m of relief contains about 90 mappable, recently active landslides ranging in size from 100 to 

50,000 m2. Outcrops are scarcer than in areas to the northwest despite the steeper slopes and greater relief. 

The slope failures are controlled lithologically; a large 

number have heads at the 800- and 900-ft contours. A discontinuous sandstone ledge of varying thickness commonly 

lies above each head area, and seeps are common at the 

contact. Poorly exposed red mudstone and shale underlie the 

sandstone. No one direction is preferred in the siting of 

landslides. 

No houses are along the hillsides and ridge crests. 

Although indications of former and current oil and gas exploration are apparent in the form of sometimes poorly defined access roads, their influence on slope failures in this 

area is believed to be minor. Most of the movements are 

largely "natural" in cause and are believed to have been 

Regional Description of Slope Movements 25 
Figure 23. Area north of Ohio 26. 

26 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 

• Recently active slope failure 

A Movement described in text 

Boundary of map area 

1 KILOMETER 

1 MILE 
generated by above normal rainfall. 

A wetter and warmer than normal December 197 4 and 

January and February 1975 probably caused high pore-water 

pressure buildup in the soils and triggered a massive movement ( 180 m wide and 90 m long) that threatened three 

houses at the foot of the slope above Ohio 7 in early March 

Figure 24. Head of the earth flow (fig. 19, locality A). Shown 

are the upper left margin of the scarp (A) and the basal shear 

surface (B). 

1975 (locality A) (Marietta Times, March 13, 1975). Fortunately, the houses still are standing (as of 1984) despite the 

ominous 2-m-high toe of the movements a few meters away 

from the rear wall of one of the houses. 

Examination of the slope above the houses in 1983 

revealed no fresh transverse cracks. Areas laterally adjacent 

Figure 26. Earth slump along Brush Run (fig. 23, locality C). 

Shown are the lateral margins (A) and the creek (B). Note the 

group of rotated trees between A and B. 

Figure 25. Earth flow within the concave slope (contour cavity) (fig. 23, locality A). Shown are the less than 1-m-high head 

scarp (A), the toe (B), and the dense, brushy area that conceals the seep (C). 

Regional Description of Slope Movements 27 
39°25 

• Recently active slope failure 

A Movement described in text 

0 CONTOUR INTERVAL 20 FEET 

0 1 KILOMETER 

Figure 27. Area south of Ohio 26. 

1 MILE 

to the threatening movement showed several episodes of 

probable contemporaneous or slightly older slope failures 

with successive fronts. Heads of major failures are at the 

800- and 900-ft contours along a 27° (52-percent) slope. 

Shallow planar earth-flow-type movement is suggested for 

the 1975 failure, during which soil and colluvium as much 

as 1. 8 m thick was removed from the head area. Deepseated (rock) slumping cannot be discounted for older 

movements, however. 

Elsewhere in the area, slopes adjacent to the heads of 

earth flows range from 8° (14 percent) to 28° (54 percent) 

with the average being about 18° to 19° (33-35 percent). 

Some slumping (mostly shallow) in head areas takes place 

in about 20 percent of the movements. Lithologically controlled earth flows are apparent at the 800-ft contour along 

the north-facing slope above Long Run in the northern part 

of the area. 

DISCUSSION OF GEOLOGIC AND OTHER 

FACTORS INVOLVED IN SLOPE FAILURES 

Lithology, Stratigraphy, and Structure 

The slopes most susceptible to movement are those 

slopes overlying relatively thick intervals (greater than 8-

10m) of shale-mudstone with a few sandstone interbeds. 

The proportion of shale versus mudstone in the interval does 

not seem to be critical. Generally, competent rock (sandstone) comprises no more that 15 percent of the sections 

underlying severely slide-prone slopes; for example, lithologic sections (fig. 3) at March Run, Hadley Run, Ohio 26 

East, Stanleyville, and the ridge to the east of Devola include a high percentage of weak rock relative to competent 

rock. 

Conversely, the lack of significant slope movements 

near the eastern edge of the study area to the east and 

northeast of Brush Run (figs. 3, 23) is a reflection of the 

greater abundance of sandstone and thinner units of shalemudstone in the section. Also, the dominance of sandstone 

along the lower slopes bordering Devol and Russet Runs and 

the upper part of Dodge Run (figs. 3, 4, 6) in the western 

part of the region seems to prevent the development of 

landslides in that area. 

Seeps are common at the contact of permeable cliffforming sandstone and underlying less permeable, poorly 

exposed shale and mudstone that form more moderate 

slopes. Movements in the colluvium and at the colluviumbedrock interface (figs. 2B-C) originate below the seeps. 

Slope movements are not concentrated within any 

particular stratigraphic unit. The density of slope move28 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
EXPLANATION 

.. Recently active slope failure 

A Movement described in text 

Boundary of map area 

0 1 MILE 

0 1 KILOMETER 

CONTOUR INTERVAL 20 FEET 

Figure 28. Area north of Ohio 7. 

ments is fairly uniform throughout the Monongahela and 

Dunkard Groups. Also, no discernible difference in the 

stratigraphic units is apparent with respect to proportion of 

competent and incompetent units. More than 90 percent of 

the slope movements occur in the Upshur soil series 

(table 1). 

Structure contours (Collins and Smith, 1977) indicate 

a regional dip of less than 1 a to the south, southwest, and 

Discussion of Geologic and Other Factors Involved in Slope Failures 29 
southeast. No relation exists between the regional dip and 

the landslide distribution. In fact, most slope movements are 

on east- and north-facing slopes except for those facing the 

Ohio River. No correlation between dip direction and landslide occurrence was found in West Virginia (Lessing and 

others, 1983) or in the Pittsburgh region and Greene 

County, Pa. (Pomeroy, 1982a, 1986). 

Slope Features 

Configuration 

Recent and old slope movements occur more commonly on concave slopes (contour concavity as well as 

profile concavity). About 60 percent of the recent movements have failed along concave slopes. This percentage is 

similar to that reported by Lessing and others ( 1983) in West 

Virginia and by Pomeroy ( 1982b) in Washington County, 

Pa. Approximately 32 and 8 percent occur on laterally planar and convex slopes, respectively. Convex slopes are expected to be better drained than adjacent slopes because soil 

moisture diverges from the slope. Soil is also usually thinner 

on noses of slopes. 

Areas of contour concavity are responsible for the 

convergence of surface and subsurface flow that increases 

pore-water pressure and decreases shear resistance. Rapid 

weathering of the regolith is characteristic of concave slopes 

because of the overall wetness. 

Angle-Grade 

Areas adjacent to the head areas of earth flows and 

related forms have slope angles from 8° (14 percent) to 33° 

(65 percent). Most took place on slopes that have a 20- to 

35-percent grade (12°-20°), and movements were less common on slopes of less than 20-percent grade (12°) and were 

rare on those of less than 15-percent grade (9°). Studies of 

slopes in other areas with abundant earth flows (San Francisco Bay area, California, southwestern Pennsylvania, and 

central and western West Virginia) yield comparable data 

(Keefer and Johnson, 1983; Pomeroy, 1982a, b; Lessing 

and others, 1976). 

Orientation (Aspect) 

The relation between slope aspect and slope failures 

was investigated for the entire region. Approximately 1 ,500 

point samples of slope aspect chosen from a grid overlay 

demonstrates a lack of any particular trend in aspect distribution. Orientations of slope movements were tabulated for 

all parts of the region, and a summary graph showing the 

number of recently active movements versus direction was 

constructed (fig. 29). 

Slightly more than 60 percent of the movements face 

east or some component of north. Slightly more than 69 

percent of the failures larger than 100 m in maximum dimension face east or some component of north. Numerous 

examples of aspect control on slope stability have already 

been given (fig. 4, localities A, B, H; fig. 23, locality G). 

In general, hummocky ground is more common on northfacing slopes than on south-facing slopes. 

Several factors contribute to the high incidence of 

earth flows and slumps on north- and east-facing slopes. 

Slopes facing north receive less exposure to the sun; after a 

rain, soils remain wet longer than soils on south-facing 

slopes. East-facing slopes receive early morning sunlight, 

but the drying effect on soils is ineffective because of the 

low temperatures at that time of the day. Snow cover lingers 

longest on slopes facing northwest clockwise to east.· Conversely, higher rates of evapotranspiration are found on 

200 

150 

w 

> 

i= 

u 

<( 

>- -I 

Iz 

w 

u z w 0 

~ u; 

z en 

w ~ 100 0 0 ::::::i :::i! en ::I 0 :::i! z x <( <( -I :::i! u.. 

0 ~ 

a: E 

w 8 ID 1\ ::::!!: 

::J 

z 

SSW WNW N NE E SE S SW W NW N NE E 

ORIENTATION OF SLOPE 

Figure 29. Orientation of recent slope failures in the Marietta 

area. 

30 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
south-facing slopes. As a result, north- and east-facing 

slopes generally have a higher moisture content than do 

south-facing slopes. These slopes tend to be more unstable 

with the advent of additional precipitation. 

Surface Drainage and the Influence of 

Microclimate 

Slopes with a well-developed surface drainage network (fig. 15) show relatively few movements. Surface 

drainage networks should speed runoff and lower local slope 

water tables to give drier, well-drained slopes. Hence, 

drainage channels minimize pore-pressure buildup and convey stability. Well-drained slopes with linear channels 

spaced at least every 30 m (across slope) were noted at 31 

localities in the Marietta area. More than 45 percent of these 

well-drained slopes fall southwest, and an additional 26 

percent face west and south. South-facing slopes receive 

significantly more solar radiation than do other slopes at the 

time of winter and early spring thaws of snow, yielding 

greater runoff and channel erosion. Repetition of these conditions over thousands of years has left a drainage imprint 

that is apparent, at least locally. 

Microclimatic influences on southwest- and 

northeast-facing slopes became apparent during the investigation. Southwest-facing forested slopes show an abundance of mixed oak species, whereas a more heterogeneous 

assortment of trees, dominated by faster growing varieties, 

but including oak, and accompanied by more brush and 

vines, characterizes the northeast-facing slopes. The dominance of undergrowth under a mature forest is common on 

poorly drained, generally unstable slopes; for example, locality Kin figure 6 is a northeast-facing wet slope that was 

difficult to traverse in early spring because of dense undergrowth. No recently active landslides could be detected on 

this slope; however, a widespread, somewhat subtle hummocky surface of low relief indicates continuing soil creep 

and periods of old landsliding. The appearance of this slope 

is in marked contrast to the well-drained (dry) woodland 

without undergrowth and noticeable creep on the opposing 

southwest-facing slope. Similar distinctions have been recognized elsewhere in the Appalachian Plateau region of 

southeastern Ohio at Neotoma Valley, Hocking County 

(Finney and others, 1962), where rocks of Mississippian to 

Pennsylvanian age underlie the surface. 

Excellent examples of controls on the distributions of 

outcrops, colluvium, and landslides are ubiquitous throughout the tributary valleys to major streams but particularly on 

the slopes along the most deeply entrenched 1.5-km-long 

part of Brush Run which empties into Duck Creek (fig. 23). 

Similar controls have been noted by Wolfe and others 

(1943) at Neotoma Valley in Hocking County, where considerable differences in sunlight, soil temperature, and 

moisture have been recorded between northeast- and 

southwest-facing slopes (Finney and others, 1962). These 

factors might tend to produce a more deeply weathered and 

thicker mantle of rock and soil on northeast-facing slopes 

and a greater density of slope movements in the Marietta 

area. 

In addition, snow on south-facing slopes melts faster, 

increasing the probability that snow melt will be dispersed 

as runoff over saturated soils. Snow on north-facing slopes 

melts slower allowing for slower, more even infiltration and 

dispersal of moisture as subsurface flow. I have observed 

moderate to rapid thaw periods in late March when southfacing slopes, almost bare of snow, show running water. At 

that time, the north- (and east-) facing slopes do not show 

rapid melt, and a thin snow veneer is still present. Rill wash 

and sheet wash were noted on the southwest-facing slope in 

the Neotoma Valley (Everett, 1963). 

The effects of microclimatic differences on slopes can 

be recognized in the Marietta area. Because southwestfacing slopes are generally better drained and a thicker regolith seems to exist on northeast-facing slopes, instability 

is more common on the latter slopes. A surface drainage 

network produces a deeper water table; a lack of network 

shows a higher water table over longer periods during the 

year. 

Valley Stress Release 

Stress release might be a significant factor in controlling the siting of slope failures along major drainages. 

Ferguson (1967) made observations about stress release at 

foundation excavations for dams in the Appalachian 

Plateau. Further discussion by Ferguson and Hamel (1981) 

and application to other areas of the Appalachian Plateau by 

Wyrick and Borchers (1981) and Pomeroy (1982a, 1984c) 

showed that stream erosion, having removed horizontal support from valley walls, has caused an unequal stress distribution resulting in vertical fracturing and bedding-plane 

slippage along valley sides. These steeply dipping to vertical joints are parallel to major drainages and many tributary 

valleys throughout the Appalachian Plateau. Stress release 

intensified during the Pleistocene, when melt water from the 

retreating icecap deepened valleys. 

Fractures inferred to be stress relief features alter hillslope hydrology and promote weathering. As contended by 

Wyrick and Borchers (1981), meteoric water moves through 

stress relief jointed rock (secondary permeability) penetrating downward to an impermeable horizon, such as mudstone or shale, where it is emitted to the soil surface as a 

seep. Water passing through vertical fractures to an impermeable horizon has been implicated in the origin of rock and 

earth slumps (Pomeroy, 1982a, 1984c). In addition, bedrock subjected to secondary permeability is weathered easily 

because of increased infiltrating water. 

Slopes facing major drainages, such as the Ohio 

River, are particularly prone to downslope movements beDiscussion of Geologic and Other Factors Involved in Slope Failures 31 
cause of the accumulation of weathered bedrock. Blocks 

have separated along joints and moved downhill; some rock 

masses have slumped or failed along subsurface planar surfaces. 

In the Marietta area, closely spaced, wide vertical to 

near vertical tension joints are found along the Ohio River 

and, to a lesser extent, along the Muskingum River and 

Duck Creek. Prehistoric rock slumping and rock fall, probably taking place along stress release fractures, occurs along 

the southeast-facing slope northwest of Lower Newport 

(fig. 28). A possible rock slump might have been generated 

by the same process along the west-facing slope to the east 

of the Muskingum River (fig. 10, locality G). 

Vegetation 

An attempt was made to correlate slope movement 

with forest cover (or lack of it). The percentage of the area 

covered by woodland has increased from 1943 to the present 

time. The reforestation has been caused mainly by abandonment of land used for crops and pasture. One might assume 

that the likely continuation of this trend possibly could stabilize slopes in time, assuming a period (decade?) of decreased precipitation and limited slope modification. 

I have already noted that poorly drained, unstable 

slopes commonly are characterized by dense undergrowth. 

Undergrowth develops quickly along a slope where failure 

has taken place. Extensive disruption of the land surface 

commonly kills the mature forest growth. 

My studies suggest that recent movements are just as 

likely to occur along longstanding forested slopes (based on 

1943 aerial photographs) as on grassland slopes. Also, 

grasslands that existed in 1943 and whose vegetative cover 

has not changed are sites for continued movement (frontispiece). One cannot overlook the fact that many areas 

showing a high concentration of slope movements are 

forested (fig. 4, locality H; fig. 10, locality G; fig. 16, 

locality B; fig. 28). Of course, steep slopes generally are not 

cleared. 

However, Riestenberg and Sovonick-Dunford (1983) 

reinforced the belief of most slope movement mappers that 

tree roots increase the factor of safety against sliding several 

fold. They found that tree roots markedly stabilize colluvium on steep hillsides in southwestern Ohio and cited the 

findings of several investigators who demonstrated either 

that roots increase the stability of soils or that soil strength 

decreases as roots decompose. Consequently, slope movement increases with time after deforestation. An alternative 

hypothesis by some researchers suggested that roots force 

cracks open deep in the regolith, thereby increasing the zone 

of weathering. In addition, slopes may be destabilized by 

the weight of the forest. Finally, some investigators pointed 

out that the trees intercept precipitation in the crown area, 

release water vapor to the atmosphere by transpiration, and, 

thereby, decrease the quantity of water absorbed by the 

slope mantle. 

Tree roots, undoubtedly, contribute to the stability of 

slopes. However, other factors may play an equal or greater 

role in determining the susceptibility of a slope to sliding. 

The fact that recent landslides in the Marietta area take place 

on longstanding forested slopes implies that other causes 

can be dominant. 

Precipitation 

Precipitation is the most important factor in the frequency of slope movements. The vast majority of slope 

failures are related directly or indirectly to precipitation, and 

the relation is complex rather than simple (Sangrey and 

others, 1984; Wieczorek, 1981). Most slope failures are 

believed to take place when the ground-water surface is 

high. 

Climatic records from Marietta since 1962 (National 

Oceanic and Atmospheric Administration, 1963-84) indicate that the 1960's generally were drier than normal, 

whereas the period beginning with 1970 and extending into 

the 1980's to the time of the present investigation has been 

wetter than normal (fig. 14). 

Two observation wells at Marietta are in unconsolidated sand and gravel aquifers (U.S. Geological Survey, 

1965, 1970, 1974, 1977, 1971-85). Although the records 

are incomplete, the yearly ground-water table low generally 

occurs toward the end of summer or early fall, whereas the 

yearly high commonly occurs between March and June, 

when recharge from snowmelt and spring storms is greatest. 

Data for water levels in bedrock in the Marietta area is 

lacking. Generally, these water levels can be expected to 

fluctuate more slowly in response to delayed recharge 

(Harstine, 197 5-85). 

Exceptions to this seasonal pattern do occur because 

of excessive precipitation caused by aftereffects of tropical 

storms such as those that took place in September 1975 and 

1979. A combination of scant snowpack and below normal 

rainfall coupled with above normal temperatures during the 

spring months will tend to keep ground-water levels low 

later in the year. Summer thunderstorms generally have 

little effect on the overall ground-water storage because of 

high evapotranspiration rates at that time. 

The period between October 1978 and November 

1980 in Marietta stands out as a time of unusually heavy 

precipitation and high ground-water levels (National 

Oceanic and Atmospheric Administration, 1963-84; U.S. 

Geological Survey, 1971-85). Within this 26-month (mo) 

period, above normal precipitation took place during 18 mo. 

Furthermore, monthly precipitation in excess of 5 inches 

(in.) occurred for nine of these months with a record amount 

of over 10 in. recorded at Marietta in August 1979 (National 

Oceanic and Atmospheric Administration 1963-84). The 

highest ground-water level in 34 yr was recorded in early 

March 1979 at one of the observation wells; it followed a 

record-high reading at the other well by a few days (U.S. 

Geological Survey, 1971-85). Throughout most of southern 

32 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
Ohio, high ground-water levels resulted from recharge produced by melting snow and heavy rains following a late 

February 1979 thaw (Harstine, 1975-85). Ground-water 

levels remained especially high during the remainder of the 

year because of below normal temperatures in late spring 

(reducing evapotranspiration rates) and above normal rainfall for most of the second one-half of 1979. High groundwater levels continued into 1980 with below and above 

normal precipitation in winter and spring followed by heavy 

rains during the summer months. 

No data exists that would allow one to evaluate the 

extent of landsliding during the late 1978 to late 1980 period. However, about 75 percent of the newspaper articles 

from 1973 to 1981 referring to landsliding appeared during 

1979 and 1980. 

In interviews with long-time residents of the area, 

statements to the effect that more "slides" are occurring than 

ever before are typical. Remarks pertaining to "slips" not 

being as numerous when "they" were younger are common. 

Discussions with veteran Soil Conservation Service personnel in southwestern Pennsylvania and more recently in 

southeastern Ohio indicate a relation of slope failures to 

increased precipitation and a general rise of ground-water 

levels in the regolith. High ground-water levels cause porewater pressures in the regolith to be built up during and 

immediately following any intense rainstorm or period of 

persistent rainfall along with an accompanying decrease in 

shear resistence of the regolith. This excess water contributes to new slope movements, as well as reactivating 

older slope failures. Gray and Gardner (1977) believed that 

a large-scale slope failure at McMechen, W. Va. , was triggered by high pore pressures in the soil caused by a period 

of abnormally high precipitation. 

ADVICE FOR RESIDENTS 

Landslides are common throughout southeastern 

Ohio. Slope movement activity in the Marietta area is, perhaps, slightly greater than in other areas of southeastern 

Ohio because the higher population density requires frequent cut-and-fill slope modification. 

Slope movement is indigenous not just to southeastern 

Ohio but is widespread in neighboring West Virginia, Pennsylvania, and Kentucky, as well as southwestern Ohio 

(Radbruch-Hall and others, 1982). Hamilton County, Ohio, 

which includes Cincinnati, has a higher annual cost of damage per capita than either the San Francisco Bay or the Los 

Angeles areas (Fleming and Taylor, 1980). 

Slope failures in the Marietta area are generally slowmoving resulting in few deaths and injuries. Rockfalls are 

the chief exception and possess a high potential for serious 

injury or death. Fortunately, major areas of potential rockfall hazard in the Marietta area are not as numerous as in 

other areas of the Applachian Plateau due, in part, to lower 

relief and more moderate and fewer modified slopes. The 

most critical location for rockfalls is along Ohio 7 southwest 

of Marietta (fig. 7, locality C). Interstate 77 cuts have posed 

fewer problems, in part, because of fewer sandstone exposures. 

Identification of a Slope Failure 

The following features indicate that a property may 

have a potential or ongoing slope problem: 

1. Hummocky ground.- Hummocks, low uneven or lumpy 

mounds or knolls, are common, irregularly spaced 

features of the toes and lower slope surfaces of recent 

and old landslides (figs. 11, 17, 25). Topographic 

maps in the area may show an unevenness and irregularity of contours in the lower (sometimes upper) part 

of a slope indicative of an old (probably prehistoric) 

movement. Because of a commonly low gradient in 

the lower part of a slope, development might seem 

feasible. However, the possibility of future slope reactivation is a potential hazard. 

2. Cracks in the ground.-lf the property is at the edge of 

a ridge crest, then an investigation for ground cracks 

more or less parallel to the slope below is necessary. 

Surface cracks could indicate that the site is within the 

crown area (fig. 2A) of a slope movement. The slope 

downhill from the property also should be examined. 

Any cracking across the slope points to active movement. 

3. Seeps and springs.- Unusually wet ground anywhere 

along a slope is indicative of a seep or spring. The 

time of the year is meaningful in that wet ground is 

common along many slopes, especially between 

March and May, whereas the same area might not be 

wet in late summer or fall. Seeps and springs are 

common at the toes of movements, but they are, perhaps, more common just above or in head areas of 

slope failures. Standing bodies of water anywhere 

along the slope are probably within an area of 

downslope movement. Wet or saturated ground along 

slopes is, at least, potentially unstable in response to 

gravitational downslope movement. Any poorly 

drained slope area is best left alone unless the intended 

land use justifies the cost of renovation. 

4. Areas of grapevines, reeds, horsetails, cattails, and 

tilted trees.-Grapevines and reeds have been ob-· 

served on many old landslide deposits. In these areas, 

mature trees are lacking; older trees are commonly 

dead. Poor drainage, which can lead to the development of inpenetrable brush along a slope, might indicate instability. Tilted trees do not necessarily imply 

instability (Phipps, 1974) because trees on slopes tend 

to bend outward somewhat as they seek sunlight (a 

phototropic. response). However, trees leaning at appreciable angles or numbers of trees leaning in different directions strongly suggest areas of slope failure. 

Advice for Residents 33 
5. Erratic alignment of utility lines and surface pipelines.-

Appreciable tilting of poles with variations in the 

amount of sag of the conduits usually indicates slope 

movement. A bowed pipeline across a slope indicates 

downslope failure. Evidence of former pipeline breakage might lie adjacent to the site. 

6. Cracks in houses and buildings.-Cracks tend to concentrate around openings (doors, windows). Distortion or warping of the frame of a house because of 

slope movement will cause doors and windows to jam 

or stick. However, the cause of cracking may not be 

attributed necessarily to a slope failure. 

7. Cracks in manmade features adjacent to dwellings.-

Asphalt driveways and brick and concrete walls in 

yards usually rest on soil and are sensitive to slope 

failure, which can cause cracking. Any enlarged 

cracks or out-of-plumb structures probably are caused 

by accelerated creep that may indicate incipient slope 

movement involving ground breakage. 

8. Drainage ditches that are partially filled in by soil (and 

rock) debris either along the slope or at the base of the 

slope.- Depending upon the date when the ditch was 

last cleaned, this detection could signify accelerated 

movement. 

9. Recognition of segments of an abandoned road and (or) 

house foundation ruins that are covered partially with 

slope debris.- Such an identification indicates past 

slope failure and likelihood of future slope movement. 

The prospective buyer or developer should bear in 

mind that properties on level ground, either on a ridgetop or 

in a valley adjacent to a slope, also need to be scrutinized 

closely. Level land behind a valley-sited house might be 

partially covered by a slope movement at a future date. 

Also, land at the edge of a ridgetop could be subject to 

movement either from the slope below or from failure of the 

material making up the land if the area has been filled. 

Practices That Cause Slope Failures 

Most slope movements in the Marietta area result 

from natural conditions, mainly precipitation. However, 

within the town of Marietta, many slope failures are caused 

by man-induced activities. The three most commonly committed practices are shown by sketches (figs. 30-32) that 

illustrate possible results from these actions. These practices 

are applicable to areas elsewhere in Ohio and the Appalachian Plateau part of adjacent States. No corrective actions should be taken without a site investigation by a geotechnical engineer or engineering geologist. 

1. Fill emplacement on slopes.-Figures 30A and B show 

the practice of backyard fill placed on a slope improperly and its potential consequences; figures 30 C and 

D show a less common occurrence. The most common 

loading of a slope takes place when earth materials are 

emplaced as a fill, usually to extend the backyard of 

A 

8 

House threatened 

if "landslide" 

continues moving 

+ 

c 

D 

House threatened 

if "landslide" 

continues moving 

\ 

Potential 

rupture surface 

Hummocky 

ground 

J 

Soil and 

This part of 

slope probably 

now overloaded \ 

Hummocky 

ground 

~ 

Bedrock 

House set 

on bedrock 

House 

undamaged 

"Landslide" 

deposit 

House set on soil 

and fill rather 

than bedrock 

\ 

Bedrock 

Main scarp 

"Landslide" 

deposit 

Figure 30. Possible effects of backyard fill placement. A, 

Backyard fill placed on the slope improperly. 8, Potential consequences thereof. C, Sensitive slope overloaded by backyard 

fill and house set on soil and fill. 0, Potential consequences 

thereof. Slope and soi I thickness exaggerated. 

34 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
a house on a slope or on a ridgetop. A surface of 

separation might result within the fill, between the fill 

and soil surface, within the soil and weathered rock, 

or at the contact of the weathered and unweathered 

bedrock. Most fill failures probably occur between the 

fill and soil surface. The Strecker Lane (Devola) fill 

failure (fig. 10, locality E) is an example. The extensive slope movement along the western side of Interstate 77 (fig. 10, locality A) about 3 km east-northeast 

of Devola is probably another example. 

Proper construction of a fill on a slope involves 

engineering expertise and should be designed for the 

particular slope on which it is to be placed; it includes 

removal of natural vegetation before emplacement and 

lift-by-lift compaction (Briggs and others, 1975). If 

vegetation is not removed, then surfaces of slippage 

can focus on decaying vegetation between the new fill 

and the former natural slope; if fill is not compacted 

properly, then failure can take place within it. 

Care must be exercised not to fill natural drainage 

or swales with fill. Filling of the drainages commonly 

results in a rise of the ground-water table, which leads 

to an unstable supersaturated soil mantle during and 

(or) following an intense or prolonged rainfall. 

2. Slope cutting.- Figure 31 shows the potential consequences when a sensitive slope is excavated at its 

base. Similar results could occur anywhere along a 

slope wherever a bench or flat area is desired. Because 

valleys are generally narrow throughout the Appalachian Plateau, excavation at the foot of a slope to 

make more flat land is a common practice. If the cut 

is in the toe of an unidentified old or prehistoric landslide deposit, then a slope movement could result. 

However, slope failures can occur anywhere along the 

slope if unstable soil is disturbed. 

3. Drainage changes.-Figure 32 shows a slope excessively wetted by an inadequate drainage system and its 

potential consequence. Inadequate disposal of downspout water can affect the stability of slopes and indirectly has caused slope failures in the Marietta area. 

Modification of a ridgetop for housing or a new road 

can cause drastic changes in surface- and groundwater flow along the slope below the alteration. Complete removal of vegetation may increase or decrease 

soil moisture because water that ordinarily would be 

lost by evapotranspiration may either infiltrate or run 

off as overland flow, depending on soil conditions. 

Remedial Actions 

Design procedures on unstable soil slopes were discussed by Gedney and Weber (1978) and Zaruba and Mend 

(1982). Field and laboratory investigations are necessary in 

any corrective studies conducted by a geotechnical engineer. Maximum flexibility in- the application of remedial 

A 

8 

House 

destroyed 

\ 

Potential 

rupture surface 

Bedrock 

Figure 31. Possible effects of lower slope excavation. A, Sensitive slope excavated at bottom. 8, Potential consequences 

thereof. 

A ~~~~~~/;! ;r ~ r jjl I II Rolowoted<Om 'I dow"'po"t odded 

(/ 

//I ;;1//1 / 

rupture 

Potootiol 

surface 

to~'' ~ ~ .;., ~ 

8 

House threatened 

if "landslide" 

continues moving 

Broken ground 

susceptible to 

infiltration of 

Bedrock 

House 

threatened'\ 

additional w\ater ~ ::~; '». 

Mino~ r......::...L.----LHummocky scarps-----------.. 

ground, 

"Landslide" 

deposit 

Figure 32. Possible effects of downspout water on slope. A, 

Water added to soil on sensitive slope by poor drainage system; here, a downspout. B, Potential consequences thereof. 

Advice for Residents 35 
measures is mandatory as each problem area poses different 

approaches. 

Several options should be considered by landowners 

in the Marietta area. They are (1) to avoid or eliminate the 

problem by abandoning the site, (2) to build retaining walls 

in an attempt to prevent further slope movement, or (3) to 

control surface- and ground-water movement by installing 

trench drains. 

Depending upon the circumstances and present slope 

use, the first option might not only be the least expensive but 

the only feasible approach. An on-site investigation by an 

experienced geologist or geotechnical engineer will be critical to most decisions. 

Option 2 involves the construction of a retaining 

wall(s) above the head and (or) at the toe of the movement. 

Construction of any one of a number of devices such as a 

concrete crib wall, gabion-wall retaining structure, timber 

bulkhead, reinforced concrete retaining wall, or various 

types of anchor systems can be effective but costly. However, poor drainage should not be ignored in a retaining wall 

design. 

Option 3 may be effective alone or in addition to 

option 2 in many problem areas. A backhoe can be utilized 

effectively in the construction of trench drains through the 

slide area parallel to the direction of movement. Care must 

be exercised especially during the wetter part of the year 

because trench walls will rapidly close in and fall. The effect 

of drain emplacement will be to lower the ground-water 

table along the problem slope. Drains must come to the 

surface near the base of the slope to ensure the expedient 

movement of water. 

As in most slide-prone areas anywhere in the country, 

the most successful methods for remedial work on slopes in 

the Marietta area generally deal almost entirely with groundwater control. Controls should include the following: 

1. Diversion of surface water from any area of the slide, 

especially the head area. Downspout water from adjacent housing must not enter the landslide body. 

Ditches above and parallel to the head scarp should 

have an impervious pavement. Water emanating from 

springs, commonly within the head area, should be 

directed away from the slide area. 

2. Filling and compaction of open cracks in the crown area 

of the landslide (fig. 2A ). These cracks may extend to 

the failure plane of the slide. 

SUMMARY 

Shallow-seated and planar slope movements, largely 

earth flows, in the regolith (mostly colluvium) are widespread throughout the Appalachian Plateau region of southeastern Ohio and adjacent States. Field investigations in the 

Marietta area showed that the slopes most susceptible to 

movement are those overlying relatively thick intervals of 

shale-mudstone with thinner beds of coarser grained clastic 

rock. Slope movements are less common where sandstone is 

more dominant than the less competent shale-mudstone. 

Seeps are common at the contact of permeable sandstone 

and underlying less permeable, poorly exposed shale and 

mudstone that form more moderate slopes. Movements in 

the colluvium and at the colluvium-bedrock interface originate below the seeps. No relation exists between the direction of dip of strata and the distribution of the slope movements. The density of movements is uniform throughout the 

Monongahela and Dunkard Groups. 

Over 60 percent of the slope movements occur on 

eastward- or northward-facing slopes; a greater percentage 

of large (greater than 100m in maximum dimension) failures face north or east. Well-drained slopes with channels 

about every 30 m (across slope) show few movements. 

More than 45 percent of the channeled slopes face southwest, and an additional 26 percent face west or south. A 

more deeply weathered and thicker regolith seems to be 

typical of north- and east-facing slopes; outcrops are more 

common on south-facing slopes. Because of generally 

higher antecedent moisture levels, north- and east-facing 

slopes tend to be more unstable than those facing the opposite direction. 

Slope movements have an affinity for concave slopes 

(in contour and profile). Areas adjacent to recent failures 

have slope angles varying from 8° to 28°, with most being 

from 12° to 20°. Possibly, because of valley stress release, 

slopes facing major drainages particularly are subject to 

movement. Extensive slope movements are as likely to 

occur in forested areas as on grassland slopes. 

Precipitation, the most important factor in the frequency of slope failures, has been largely above normal 

since 1970. The resultant high level of ground water in the 

regolith has caused pore-water pressures to be especially 

high during and following rainy periods. The rise in groundwater levels is accompanied by a reduction in shear strength 

of the regolith. The inventory suggests that most recent 

slope failures in the Marietta area are caused by precipitation 

rather than by construction and other slope modifications. A 

striking example is a 4. 5-km2 forested area with nearly 

90 recent slope movements at least 10 m in maximum dimension and as large as 50,000 m2• This area is largely 

undeveloped; most of the movements probably have been 

caused by above normal rainfall since 1970. 

Similar suites of clay minerals were identified in basal 

shear surfaces of landslides, in other parts of landslides, and 

from areas unrelated to any slope failure. No distinctions 

could be made in the clay mineralogy between the slickensided shear plane and nonshear plane material. The illite is 

potassium deficient, which is a condition also prevalent in 

the unstable regolith areas of western Pennsylvania. 

Determining where slope movements will occur is 

hampered by poor exposures, thinness of lithologic units, 

and rapid facies changes within short distances. 

36 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
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Journal of Science, v. 58, no. 4, p. 220-230. 

Campbell, R. H., 1975, Soil slips, debris flows, and rainstorms in 

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Foundation Division Journal, no. SM4, p. 447-473. 

Everett, K. R., 1963, Slope movement, Neotoma Valley, southern 

Ohio: Ohio State University Research Foundation, Institute of 

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Ferguson, H. F., 1967, Valley stress release in the Allegheny 

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Ferguson, H. F. , and Hamel, J. V. , 1981, Valley stress relief in 

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Finney, H. R., Holowaychuk, N., and Heddleson, M. R., 1962, 

The influence of microclimate on the morphology of certain 

soils of the Allegheny Plateau of Ohio: Soil Science of America Proceedings, v. 26, p. 287-292. 

Fisher, S. P. 1969, The geology of eastern Ohio with relation to 

slope movements: Ohio University Research Institute Proceedings-A symposium on landslides, February 26, 1969, 

Athens, p. 1-20. 

---1978, Geological aspects of the environment in southeastem Ohio (abs.): Ohio Academy of Science, 87th Annual 

Meeting, Wright State University, Dayton, Ohio, 1978, 

v. 78, p. 36 

Fisher, S. P., Fanaff, A. S., and Picking, L. W., 1968, Landslides 

of southeastern Ohio: Ohio Journal of Science, v. 68, no. 2, 

p. 65-80. 

Fleming, R. W., and Taylor, F. A., 1980, Estimating the costs of 

landslide damage in the United States: U.S. Geological Survey Circular 832, 21 p. 

Gary, Margaret, McAfee, Robert, Jr., and Wolf, C. L., eds., 

1972, Glossary of geology: Washington, D.C., American 

Geological Institute, 805 p. 

Gedney, D. S., and Weber, W. G., Jr., 1978, Design and construction of soil slopes, chap. 8, in Shuster, R. L., and Krizek, 

R. J., eds., Landslides-Analysis and control: National 

Academy of Sciences Transportation Research Board Special 

Report 176, p. 11-33. 

Gray, R. E., Ferguson, H. E., and Hamel, J. V., 1979, Slope 

stability in the Appalachian Plateaus of Pennsylvania and 

West Virginia: Rock slides and avalanches, pt. 2, Engineering sites, in Voight, Barry, ed., Developments in geotechnical 

engineering, v. 14B: New York, Elsevier, p. 447-471. 

Gray, R. E., and Gardner, G. D., 1977, Processes of colluvial 

slope development at McMechen, West Virginia: International Association of Engineering Geology Bulletin 16, 

p. 29-32. 

Hackman, R. J., and Thomas, R. E., 1978, Landslides and related 

features (Ohio, Pennsylvania, West Virginia)-Clarksburg 

1 x 2 sheet: U.S. Geological Survey Open-File Report 78-

1056, 128 pls. 

Harstine, L. J. (compiler), 1975-85, Monthly water inventory 

report for Ohio: Ohio Department of Natural Resources Division of Water, 4 p. summary for each month. 

Hooper, J. R., 1969a, Slope movements of residual clays in southeastern Ohio: Ohio University Research Institute Proceedings-A symposium on landslides, February 26, 1969, 

p. 33-57. 

---1969b, Slope stability investigation of residual clay soils of 

southeastern Ohio: Ohio State University, Transportation Research Center Research Project EES 312 Final Report, 91 p. 

Hubbard, G. D., 1908, Two notable landslides (near Waverly and 

in Monroe County, Ohio): Ohio Naturalist, v. 8, p. 287-289. 

Keefer, D. K., and Johnson, A.M., 1983, Earth flows-Morphology, moblization, and movement: U.S. Geological Survey 

Professional Paper 1264, 56 p. 

Lanyon, L. E., and Hall, G. F., 1983, Land-surface morphology, 

pt. 2, Predicting potential landscape instability in eastern 

Ohio: Soil Science, v. 136, no. 6, p. 382-386. 

Lessig, H. D., 1966, Landslide along highway in Vinton County, 

Ohio: Journal of Soil and Water Conservation, v. 21, 

p. 234-236. 

Lessig, H. D., Rubel, T. N., Brown, D. L., and Hole, Thornton 

J. F., 1977, Soil Survey of Washington County, Ohio: U.S. 

Soil Conservation Service (in cooperation with Ohio Department of Natural Resources and Ohio Agricultural Research 

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Lessing, Peter, Kolander, B. R., Wilson, B. D., Dean, S. L., and 

Woodring, S.M., 1976, West Virginia landslides and slideprone areas: West Virginia Geological and Economic Survey, 

Environmental Geology Bulletin 15, 64 p. 

Lessing, Peter, Messina, C. P., and Fonner, R. F., 1983, Landslide risk assessment: Environmental Geology v. 5, no. 2, 

p. 93-99. 

Marshall, H. E., 1969, Landslide recognition and control on Ohio 

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Mast, V. A., 1980, Distribution and engineering properties of 

landslide susceptible soils in southeast Ohio: Ph.D. dissert., 

Columbus, Ohio State University, 204 p. 

Mitchell, R. H., 1941, An unusual landslide (Ohio): Journal Geology, v. 49, 382-391. 

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185, 188, 186, 173, 187, 191, 192, 198, 195, 5, 5, 5, 6, 6, 

6, 6, 6, 6, 6, 8. 

Ohio State University Engineering Experiment Station News, 

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References Cited 3 7 
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Geological Survey Journal of Research, v. 2, no. 3, p. 371-

377. 

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scale 1:50,000. 

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48 p. 

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1618, 16 p. 

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rnicroclimates of a small valley in central Ohio: American 

Geophysical Union Transaction, v. 24, p. 154-166. 

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38 Slope Stability in the Marietta Area, Washington County, Southeastern Ohio 
APPENDIX 

;J> 

"C 

i 

:::::J 

c. 

:;(" 

Figure 4 

Locality 

(either 

representative 

specific site 

or more 

extensive 

area) 

Lands! ide type Aspect 

Average angle (and 

grade) of adjacent 

slope (to landslide 

head) 1 

Slope 

configuration Vegetation 

TriggerNatural (N) or 

construction 

activity (C) 

Notes 

A ----- Earth flows -------- NE--------- 14° (26 percent) --- Planar to concave. Forest (eastern 

part); brush 

(western 

part). 

N -------------- Red clay is basal shear surface. Occasional sandstone ledges above landslide head. 

B ----- No landslides ------ SW--------- S E E T E X T 

C ----- Earth flows -------- N components 17° (30 percent) --- Mostly concave-- Forest-------- N-------------- Largely red shale-mudstone makes up 

slide-prone slope. 

D ----- Debris avalanche---- E ---------- 33° (65 percent)--- Concave-------- -----do----- N -------------- 30-m-wide at head; 24-m-wide at toe. 

Highest head scarp at base of 6 m high 

sandstone cliff; younger (1983) head 

scarp 6 m below highest scarp; up to 

1. 2 m of regolith from head area. 

E ----- Slump-earth flow--- NE toE----- 15° (27 percent)--- Planar--------- -----do----- N -------------- 160-m-wide head scarp. 

F ----- ------- do ------- SW--------- 18° (33 percent)--- Planar to concave -----do----- C? ------------- 45-m-wide head scarp; drainage alteration from new house above landslide. 

G - - - - - Slump-earth flow 

and earth flow. 

H - - - - - Earth flows and 

slump-earth flows 

(coalescing). 

NE toE----- 15° (27 percent) to ------ do-----

230 ( 42 percent). 

N toNE----- 15° (27 percent) to Mostly planar, 

17° (31 percent). some concave. 

- - - - - do - - - - - C cutting of lowermost slope for 

access road. 

----- do----- N --------------

1.5 m of colluvium removed from head 

area of slump-earth flow; basal shear 

surface is 1 m below land surface. 

Discontinuous sandstone ledges 1.5 to 

4.5-m-thick lie above landslides. 

I------ Debris avalanche---- SW--------- 22° (40 percent) --- Mostly planar --- ----- do----- N-------------- 3-m-thick sandstone above head scarp; 

1.0-1.5 m of regolith removed from 

head area. 

J------ Slump-earth flow --- NE--------- 18° (33 percent) --- Planar --------- Grass-------- C widening of 

highway at base 

of slope. 

9-m-thick sandstone above head scarp of 

100-m-wide failure; seepage at base of 

ledge. 

K ----- Debris avalanches 

(2). 

---- do---- 22° (41 percent)--- ------ do----- Forest-------- N mostly-------- 17-18 m wide; colluvium is less than 

1. 5 m thick; seeps below sandstone 

ledge. 

;!::: 1See figure 27 of Appendix. 
~ Figure 6 ~ 

Ill Locality 

0 (either Average angle 'C Trigger- representative (and grade) of f'l) 

Slope Natural (N) or Ill specific site Landslide type Aspect adjacent slope Vegetation Notes S' configuration construction 

~ or more (to lands I ide 

extensive head)l activity (C) 

~ 

:r area) 

:r A-B----- Earth flows (coa- E ---------- 23° (42 percent) to Planar------- Mostly forest--- Nand C road Poor exposures of red mudstone-shale f'l) 

~ lescing). 33° (65 percent). widening? beneath 6.0- to 9.0-m-thick sandstone 

Ill ledge. "'I 

!!' c ------- Rockfall (not a land- SE --------- SEE TEXT S' slide). > 

~ D ------- Slump-earth flows ---- do---- 18° (33 percent) to Planar to con- Forest--------- Largely C unstable Widest and most continuous area of slid- ~ 

~ (coalescing). 22° (41 percent). cave. fill placed on ing in Marietta area. 

Ill red shale-

"' ::r mudstone :;· slope. a.s. 

Q 

::::1 E ------- Earth flows - - - - - - - Mostly NE--- 17° (31 percent) to Concave and Grass-brush- Mostly N also, Large concentration of springs below 

1""1 24° (45 percent). planar. forest. storm-water sandstone ledge feed slide-prone Q 

c runoff from slopes. ::::1 

~ subdivision 

Ill along ridge Q 

c crest on north-

:r east side of f'l) 

Ill tributary "' i drainage. ::::1 

0 F ------- Slump-earth flow - - s ---------- 19° (34 percent) --- Concave- - - - - - Grass--------- N and C storm- 2.5-m-high (>average) head scarp of 40- ::r water pipe m-wide failure; crown cracks extend s· 

breakage in- 6 m behind head scarp. 

duced by heavy 

rain. 

G------- Debris slide- - - - - - - ---- do---- 33° (65 percent) --- Planar------- Cut slope; no Nand C-------- 8.2-m-wide head scarp is 18 m above 

vegetation. Ohio 550; red mudstone-shale cut 

slope below sandstone ledge; seep at 

contact. Red clayey slickensided 

basal shear surface is within 0.3 m of 

land surface in the head area. 

H------- Earth flows, slump- N components 13° (23 percent) to Mostly concave Forest--------- N ------------- Most earth flows have basal shear planar 

earth-flows, and 17° (31 percent). within 1 m of surface. 

slumps. 

I-------- Debris slide, debris S, SE, NE--- 15° (27 percent) to Planar and con- ----- do----- ------ do----- Basal shear plane is within 1.0-1.5 m 

avalanche, earth 28° (54 percent). cave. of surface. 

flow. 

J-------- Earth flows - - - - - - - Mostly NW 15° (27 percent) to Mostly concave Mostly forest- - - ------ do----- Wet slopes below 1.0- to 4.5-m-thick 

to E. 21 o (38 percent). sandstone ledge at 860- to 870-ft elevation. 

lSee figure 27 of Appendix. 
;> 

"C 

~ ::s 

Q. 

;;(. 

~ 

w 

Figure 10 

Locality 

(either 

representative 

specific site 

or more 

extensive 

area) 

Lands I ide type Aspect 

Average angle (and 

grade) of adjacent 

slope (to landslide 

head)1 

Slope 

configuration Vegetation 

TriggerNatural (N) or 

construction 

activity (q 

Notes 

A-B---- Earth flows (2) ----- NW and W -- 17° (31 percent) --- Planar to concave Brush to grass--- C surcharging of 350-m and 100-m-wide failures in fill 

slope by high- and subjacent slope. 

way cut fill. 

C ------ Earth flows -------- NW, SE----- 21 o (38 percent) --- Concave and pia- Forest to brush -- N ------------ Wet slope beneath sandstone ledge above 

nar. head scarp. 

D ------ Earth flow--------- NW -------- 23° ( 42 percent) --- Sightly concave to Brush---------- ----- do -----

planar. 

E - - - - - - - - - - - - - do - - - - - - - ESE - - - - - - - - Renovated slope is Planar - - - - - - - - - Grass - - - - - - - - - - C - - - - - - - - - - - -

11 o (20 percent). 

F ------ Earth flows-------- E, SW ------ 16° (28 percent)--- Concave to planar. 

G------ Earth slump or rock 

slump. 

W---------- 19° (34 percent) to Planar to slightly 

25° (45 percent). concave. 

Grass to brush- -- C drainage uncontrolled? 

Forest---------- Mostly N; cutting into hill 

for house construction probably caused at 

least part of 

north section 

of failure. 

Fresh 18 m wide; uppermost sliding 

plane is 0.6-0.9 m below surface. 

Basal shear surface striations lose 

identity and diffuse into soil near head 

of movement. Digging revealed two 

other equally fresh striated surfaces 

below the topmost one. 

160-m-wide multiple backyard (largely 

fill) failure; south lateral edge preserved. 

No outcrops but lithologic control is evident with head scarps at similar elevations. 

340-m-wide failure irregular in shape; 

1.0- to 2.0-m-thick sandstone lies 

above head area. 

H------ Slump-earth flow --- S ---------- 24° (45 percent) --- Planar to convex Forest to grass -- N? ----------- 200-m-wide, 50-m-long; small house in 

1See figure 27 of Appendix. 

head area at eastern end destroyed; 

larger residence at base of slope threatened at west end. 
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Figure 16 

Locality 

(either 

representative 

specific site 

or more 

extensive 

area) 

Landslide type Aspect 

Average angle (and 

grade) of adjacent 

slope (to landslide 

head) 1 

Slope 

configuration Vegetation 

A ----- Slump-earth flow --- N ---------- ----------------- Concave------- Grass --------

B ----- Earth flows -------- NW -------- 18° (33 percent) to Concave to pla- Forest to grass 

220 (40 percent). oar. 

C----- NO DATA -------------------EXACT LOCATION NOT KNOWN 

D----- Earth flow--------- S ---------- 9° (15 percent) ---- Slightly concave Grass--------

to planar. 

TriggerNatural (N) or 

construction 

activity (C) 

Mostly C - - - - - - - -

Mostly N- - - - - - - -

Not known what 

caused earth 

flow which 

broke waterline. 

Notes 

Fill and subjacent colluvium are in an 

ancient landslide. 

Scant outcrop indicative of weak 

mudstone-shale underlying colluvium. 

Failure appears to be in crown area of an 

ancient landslide. 

E ----- ------- do ------- E ---------- 13° (23 percent) --- Concave to pia- ----- do ---- Probably N ------ Extremely slow moving earth flow; part 

oar. of movement is due to creep. 

F ----- Slump-earth flow --- S ---------- 14° (25 percent) --- Concave------- Brush to forest N-------------- Unique slope failure in that essentially all 

1

See figure 27 of Appendix. 

of ancient landslide has been reactivated. Landslide (350 m wide) is 

largest within town limits. 
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Figure 19 

Locality 

(either 

representative 

specific site 

or more 

extensive 

area) 

Lands I ide type Aspect 

Average angle (and 

grade) of adjacent 

slope (to landslide 

head)1 

Slope 

configuration Vegetation 

TriggerNatural (N) or 

construction 

activity (C) 

Notes 

A----- Earth flows (2) ----- N ---------- 18° (32 percent)--- Concave-------- Grass-------- N? ------------- Seepage in head areas that lie below sand 

stone ledge. 

B ----- Earth flow--------- SE --------- 13° (23 percent)--- ------do ----- Grass to brush N -------------- >100m in width seepage at base of 1-

m-high head scarp. 

C ----- ------- do ------- W---------- 17° (30 percent) --- ------ do ----- Forest-------- ------ do ------ 24-m-wide movement, basal shear plane 

is 1 m below surface. 

D ----- Earth slump-------- SW--------- 13° (23 percent) --- Planar --------- ----- do ----- C? drainage from 

road "funnels" 

into head area. 

E ----- Slump-earth flow --- ---- do ---- 29° (55 percent) --- ------ do ----- - - - - - do - - - - - C pipeline emplacement above 

head scarp; 

drainage 

changes. 

50-m-wide rotational movements extends 

to foot at drainage; sandstone ledge 

above head scarp. 

Sandstone capping of top of ridge, red 

mudstone below; very fresh 25-m-wide 

landslide. 

F ----- Earth flows -------- Multidirectional. 

17° (30 percent) --- Mostly concave-- ----- do ----- N -------------- Clearly shows affinity of large slope 

movements to hollows or coves. 

Isee figure 27 of Appendix. 
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Locality 

(either 

representative 

specific site 

or more 

extensive 

area) 

Landslide type Aspect 

Average angle (and 

grade) of adjacent 

slope (to landslide 

head) 1 

Slope 

configuration 

A----- Earth flow--------- N to NW---- 22° (40 percent) --- Planar --------

B ----- ------- do ------- NE--------- 16° (28 percent)--- Concave-------

Vegetation 

Forest--------

Grass - - - - - - - -

TriggerNatural (N) or 

construction 

activity (C) 

N --------------

------ do ------

Notes 

24-m-wide head area; regolith has been 

displaced 3.0-3.5 m. 

Seepage in head scarp and below steeper 

slope. 

C ----- Earth slump-------- E ---------- horizontal (0°)----- -------------- -----do ---- ------ do------ 14-m-wide, 6-m-long with 1-m-high head 

scarp; basal shear surface lies beneath 

creek channel. 

D ----- Earth flow--------- N toNE----- 21° (38 percent)--- Concave------- ----- do ---- ------ do ------ Widest farmland earth flow (400 m wide) 

in Marietta area. 

E ----- Mostly earth flows, 

some slump-earth 

flows. 

Multidirectional; 

largest failures face 

N. 

17° (30 percent) --- Concave and 

planar. 

Mostly forest-- N except for 

garbage dump. 

Smaller movements along south-facing 

slope have not been caused by any 

slope modification; slippage of garbage 

and soil discernible on 1968 aerial 

photographs. 

F ----- S L 0 P E M 0 V E M E N T S A R E S C A R C E T 0 N 0 N E X I S T E N T (S E E T E X T) 

G----- Mostly earth flows, 

some slump-earth 

flows. 

1

See figure 27 of Appendix. 

Mostly N or 23° (47 percent) --- Mostly concave- Forest--------

NE-facing. 

N -------------- Seepages at base of sandstone ledge, area 

underlain by weaker rock than that at 

locality F. 
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Figure 27 

Locality 

(either 

representative 

specific site 

or more 

extensive 

area) 

Landslide type Aspect 

Average angle (and 

grade) of adjacent 

slope (to landslide 

head) 1 

Slope 

configuration Vegetation 

A----- Earth flow (upper SW--------- 25° (47 percent)--- Planar-------- Forest to brush 

part). 

Earth slump (lower 

part). 

B ----- Slump-earth flow--- W---------- 16° (29 percent)--- ------do----- Forest--------

TriggerNatural (N) or 

construction 

activity (C) 

Notes 

N -------------- Seepage at base of 9-m-thick sandstone 

cliff lies above head scarp. 

Probably C ------ Pipeline and access road possibly triggered movement. 

C ----- Earth flow--------- SW--------- 14° (26 percent)--- Planar to slightly ----- do ---- Probably C slight Head scarp lies at base of sandstone 

ledge; toe of earth flow has been recontoured. 

concave. slope modification for golf 

course fairway. 

D ----- ------- do------- ---- do---- 18° (33 percent)--- Concave------- ----- do ---- N -------------- Nearby lithologic section (10, fig. 3) indicates that 85 percent of interval 

along slope is mudstone-shale; 15 percent is sandstone. 

E ----- Earth flows and E toNE----- 17° (31 percent) to Mostly concave ----- do ----

slump-earth flows. 24° (46 percent). 

F ----- Earth flows-------- SW--------- 15° (28 percent) to Mostly planar-- ----- do ----

190 (35 percent). 

Percent of slope= 25.. x 100 y 

X 

------ do ------ Largest movement is in 150-m-wide cove 

and consists of several overlapping 

earthflows. 

------ do ------ Opposing (northeast-facing) slope is 

hummocky but without any recent 

landsliding. 




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