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Slumping Animations

Slumping Background

Time-lapse Animations

SLUMPING ANIMATION

RIVERBANK SLUMPING

SLUMPING BACKGROUND

Soils near the Red River and its tributaries are inherently weak and natural forces are always moving the river channels. These soils display weak engineering properties and when exposed to the slopes of the riverbanks and valley walls their high plasticity frequently and naturally leads to foundation shifting and pavement failure.

Despite the vulnerability, these prone areas have in recent years undergone extensive urbanization, leading to an artificial acceleration of riverbank slumping and instability. This natural process is often accelerated by the following homeowner activities:

House Placement
Houses are often built too close to the riverbank where the soils are most susceptible to bank instability. The weight of the structure places pressure on the riverbank and increases soil hydration because of increased storm water runoff. When the riverbank begins to actively slump, the placement of the home close to the river often provides homeowners little options except to move the house off the property.

Water
Irrigation systems and septic drain fields add extra weight and excessive water, both reducing the soil's structural strength. The saturating the soil only decreases the strength of these already weak soils and is one of the biggest contributors to increased and accelerated slumping.

Weight
Adding additional weight to the riverbank with houses, structures, retaining walls, riprap, soil and fill, and extensive landscaping places greater pressures on the riverbank and can increase and accelerate riverbank slumping.

Vegetation
Replacing deep-rooted, native vegetation with shallow-rooted vegetation, which further weakens the soils. The shallow roots of turf grass provides little soil strength and the absence of trees diminishes water removal from the soils.

TIME-LAPSE ANIMATIONS

Examples of slumping from the Fargo-Moorhead region

SOLUTIONS

Because riverbank slumping is a natural process and often inevitable, attempts to stop it have not typically proven successful. Attempted bank stabilization techniques including lime stabilization and homeowner constructed retaining walls have not proven successful. Many homeowners also confuse riverbank slumping with erosion and place riprap, concrete, or other material on the slope in an attempt to stop the erosion; the added weight of these materials on the riverbank often accelerates the slumping.

Even professionally engineered techniques such as riprap or sheet piling have not typically proven successful for single sites and often require application to large stretches of the riverbank to be successful. The costly costly design and construction associated with these techniques is often cost prohibitive to the average homeowner.

The best solution to this natural process is not building too close to the riverbank in the areas most susceptible to bank instability. Landowners are also highly encouraged to reduce their activities that accelerate this natural process by limiting the artificial introduction of water on their property, limiting the amount of weight on the riverbank, and maintaining or planting deep-rooted vegetation.

BROCHURES & ARTICLES

Cass County River Setback

This brochure has been designed for any land owner whose lot includes a Cass County riverfront setback. The brochure will help the owner understand the restrictions within the setback, the reasoning behind the setback, and the importance of both homeowners and their neighbors complying with the setback.

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Protect your Property and Watershed

A brochure targeting riverfront owners about the cause of riverbank slumping and those activities that accelerate the problem.

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Living with the River

A brochure targeting riverfront owners to educate them about the importance vegetation plays in riparian health and riverbank stability.

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A City on Stilts

An article written by C. Jelsing in the Fall 2005 NDSU Magazine about the geology and soils of the Red River Valley and their impact on the engineering and construction of buildings and soil instability.

LINKS

Slope Instability and Mass Wasting
A web page maintained by NDSU Geologist Dr. Donald Schwert; outlining the cause, problem areas, types of riverbank instability, case studies, and mitigation of the problem. This is the most comprehensive web site relating to riverbank slumping.

A Geologist’s Perspective on the Red River of the North: History, Geography, and Planning/Management Issues

Fargo Geology
A web site outlining the geology of the Fargo-Moorhead Region and provided in public service by the NDSU Department of Geosciences.

Red River Basin Riparian Project
The Red River Resource Conservation and Development (RC&D) Council and the Red River Regional Council (RRRC) directly assists landowners with the restoration, protection and management of 105 river miles of riparian area.

Red River Basin Riparian Project Links

Photo Essay on the Stockwood Fill
In 1906, the Northern Pacific Railway undertook the construction of a railroad grade in northwestern Minnesota. This photo essay covers the toils faced during the project caused by the regions unusual and weak soils.

Riverbank Collapse in northwestern Minnesota: an over view of vulnerable earth materials

NEWSPAPER ARTICLES

Unstable soils add to costs of library plot
By Mike Nowatzki