Final exam Flashcards
What is rills?
channels so small that they can be obliterated by normal tillage operations
Topography
Refers to the geometry of the land scape
Ephemeral gull erosion
Occur within field sized areas where land-disturbing operations take place.
The microtopography of the surface cause erosion to form again in the same location
why does vegetation reduce erosion
Vegetation has the potential to protect the surface against water (raindrop impact and run-off) and wind pressures, and allowing any excess surface water to infiltrate the soil
What to think about when u try to prevent erosion?
KE of raindrops Support infiltration increase retention capacity decrease surface runoff velocity improve soil structure and porosity improve biological activity (structure, porosity)
How to protect against wind erosion?
Increase surface roughness
reduce wind speed(velocity)
reduce mechanical damage of plants
- Erosion Control BMP
2. Sediment Control BMP
- = stop soil moving from original location
2. = trap soil that‘s already moved
Reasons to measure erosion
Erosion measurement (EM) and estimates provide the basis for:
- Government policies and programs
- Allocation of government resources
- Regulation of environmental
impact resulting from human activities
-conservation planning
Characteristics influencing erosion and sedimentation
- Weather and climate
- Soil properties
- Topography (+ surface roughness)
- Vegetation (canopy, ground cover, plant types, production levels)
- Land management (+types and intensity of land-disturbing activities)
Which are the types of Measurements scales?
- Temporal
- From tainstorm/winddstorm to several years
- Storms of various return period (N-yers) - Spatial
- Range from interrill/rill sediment source from hillslope to sediment discharege from catchments
-From small plots to entire regions
Technique choice depends on:
- Erosion process to be measured
- Temporal and spatial scale
- Uses of collected data
- Available time, personnel, financial resources
The Measurement plan – three steps:
- Selecting M site (where)
- M frequency and duration (when)
- M techniques for erosion processeses and envi conditions (how)
Evaluating E-control practices =
Preformance X Costs + ease of installation + maintanance
How to measure wind erosion
Measure of INFLOW vs OUTFLOW
(Increase = wind erosion)
(Decrease = Deposition)
Numerous M sites to collect all of sediment
Scientific erosion research
- Conducted to improve our understanding of erosion
- Needs carefully constructed research design
- Field measurements
- Laboratory measurements
What does USLE stand for?
Universal soil loss equation.
usle predicts long-term average annual rate of erosion
A = RKLSC*P
A= potential long-term average annual soil loss in
tones per hectare per year
R= rainfall pattern(rainfall-runoff erosion factor.
K=soil type(Soil erodibility factor)
L=Slope length factor
S= Slope steepness factor
(L+S= topography)
C = Crop system (cover management factor)
P=Management practices (is a supporting practices factor)
4 ways to measure erosion
1 Change in weight
- Change in surface elevation
- Change in channel cross-section dimensions
- Sediment collection from Erosion plots and catchment.
On what principle is the measurement “change in weight” based on, And when is it used?
Erosion M by a change in wait is based on the principle that erosion removes material from the source area.
Technique is generally used in lab or field with small soil samples.
On what principle is the measurement “change in surface elevation” based on, And what M techniques is used?
It is based on the principle that erosion and deposition by water or wind change the elevation of the land surface.
- Erosion stakes and pins
- Erosion bridges and frames
- Photogrametic methods
- Laser scanning of topography
Where is the measurement “change in cross-sectional dimensions” used?
Rills and other small channels. –> small areas are measured whit a rill profile or micro-roughness meter.
Bigger channels –> Generally survey equipment. Permanent bench marks are implemented on either side of the channel.
What can u measure with Sediment collection from Erosion plots and catchment?
- Soil detachment by raindrop impact
- Interrill erosion
- Rill erosion
- Total erosion
- Sediment yield
