Analysis Of Hydrological Erosion Risk

ANALYSIS OF HYDROLOGICAL EROSION RISK FOR THE ST. MARY BASIN, MONTANA, USA

Silvia Vittozzi

Master di 2° Livello in “GIS e telerilevamento per la pianificazione Geoambientale”

UNIVERSITA’ DEGLI STUDI DI ROMA “ROMA TRE”

30 Giugno, 2008

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THE PURPOSE OF RESEARCH

IS TO ESTIMATE

THE MOST EXPOSED AREAS TO SOIL EROSION

IN THE UPPER ST. MARY BASIN, MONTANA,

USA

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Source: www.wikipedia.org

WATERTON-GLACIER INTERNATIONAL PEACE PARK

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Hydrology

Upper Old Man River watershed; in the South of the map, the affluent St. Mary river. Source: www.uoguelph.ca

Saskatchewan River watershed. Source:www.wikipedia.org

St. Mary River Km 200Oldman River Km 362South Saskatchewan Km 1,392 kilometers

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THE SOIL

• Is basic for all life’s form.

• Encloses elements:

– biological

– mineral

• Is a natural resource

• it need long time to be created (geological ages!)

• It need to be conserved

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Soil erosion by waterRAINFALL causes rills and sheet erosion

Fonte: Marco Acutis DiProVe, marco.acutis@unimi.it, www.acutis.it

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SOIL LOSS CAUSED BY WATERDepend on:

• amount and intensity of rainfall and runoff.• land cover which reduce the direct forces of rainfall• susceptibility to erosion (texture, composition,…)• topography of the landscape as described by slope length,

steepness and shape.• Artificial conservation practices (terracing, canalizations)

and land use.

THE GIS IS A POWERFUL TOOL WHICH CAN MANAGE

TOGETHER ALL THESE ELEMENTS

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DEM resolution 10 m

Fonte : USGS

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USLE

= UNIVERSAL SOIL LOSS EQUATION• Long terms (annual)• In a determinate area

• In this case: Upper St. Mary watersheed

• A standard method to map the potential risk and erodibility of soil

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USLE

It was conceived:– In USA – In 1978 – Wischmeier and Smith (USDA)– For the field. Subsequently was applied also at not only agricoltural areas

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USLEA = R * K * LS * C * P

• A = potential mean annual soil loss

• R FACTOR = rainfall factor• K FACTOR = soil erodibility factor• LS FACTOR = topographic factor• C FACTOR = land cover factor• P FACTOR = conservation practices (terracing)

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THE USLE MAP

• It show:– The Potential erosion– The areas where rise RILL EROSION and SHEET

EROSION

• UNITA’ In English Units: tons /hectar/year

• DATUM: NAD83

10/04/2023 17Shape file ottenuto dalla classificazione del data set: Vegetation Map - Waterton-Glacier International Peace Park Vegetation Mapping Project. USGS-NPS 1999 Glacier National Park-

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DATA SOURCES of rainfall data:

United States Mean Annual R-factor, 1971-2000 spatial grid

•Unità di misura : (100’s ft-tons in h-1 ac-1 yr-1) * 10 •DATUM : WGS72 •PRISM Group (Parameter-elevation Regressions on Independent Slopes Model) climate mapping

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DATA SOURCES soil

USDA State Soil Geographic (STATSGO) Data Base for Montana

•Coverage•NAD1927

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DATA SOURCES Land useUSGS-NPS 1999 Glacier National Park Vegetation Map - Waterton-Glacier International Peace Park Vegetation

Mapping Project. Shape file, NAD 83 .

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