EROSION AND SEDIMENT TRANSPORT
MECHANISMS EXAM QUESTIONS AND
100% VERIFIED ANSWERS!!
What is the formula for specific degradation (D) in the Fournier index?
D = aC - b, where C = p²/P, and a and b are coefficients depending on the orographic coefficient.
What does the rainfall erosivity index (R) measure according to David and Collado (1987)?
It measures the number of erosion index units for a year based on daily rainfall totals greater than
25 mm.
What is the formula for calculating rainfall erosivity (R) according to David and Collado
(1987)?
R₁ = A • Π P₁, where A = 0.002 and m = 2.
What are the two classes of soil properties that influence soil erodibility (K)?
1. Properties affecting infiltration rate and permeability. 2. Properties resisting dispersion,
splashing, abrasion, and transport forces of rainfall and runoff.
What is the dispersion ratio as defined by Middleton (1930)?
It is the ratio of the weight of clay and silt in non-dispersed samples to the weight of clay and silt
in dispersed samples.
How is the erosion ratio defined in relation to the dispersion ratio?
The erosion ratio is the dispersion ratio divided by the ratio of colloid to moisture equivalent.
What indices did Lutz (1934) and Bouyoucos (1935) suggest for estimating soil erodibility
(K)?
They suggested that the clay ratio, or % sand and silt over % clay, is a good index of K.
What is the formula for calculating soil erodibility (K) according to Wischmeier and
Mannering (1969)?
, K = [(0.043 pH) + (0.62/OM) + (0.0082S) - (0.0062C)]Si.
What do the variables in the soil erodibility formula K represent?
K = soil erodibility factor, OM = organic matter content (%), S = % sand, C = clay ratio (% clay
/ (% silt + % sand)), Si = % silt / 100.
What is the consensus among researchers regarding the effect of slope on soil loss?
The only consensus is that E (total soil loss) is proportional to S (slope) raised to an exponent b,
expressed as E α Sb.
What does the equation Re = 0.1 + 0.21S^(4/3) represent?
It represents the relative soil loss (Re) to unity loss from a 3% slope, where S is the slope in
percentage.
What is the significance of the hydraulic radius in relation to slope length?
As slope length increases, the hydraulic radius increases with flow depth, leading to greater
detachment by runoff.
Why is sufficient data important for calculating erosion and sediment transport in the
Philippines?
Because the calculations of R for each storm and annual summation require a significant amount
of data that is often unavailable.
What is the relationship between rainfall distribution coefficient (C) and specific
degradation (D)?
There is a strong correlation where specific degradation (D) is influenced by the rainfall
distribution coefficient (C).
What does the variable P represent in the context of the rainfall erosivity index?
P represents the daily rainfall total greater than 25 mm.
What is the role of soil management in influencing soil erodibility (K)?
MECHANISMS EXAM QUESTIONS AND
100% VERIFIED ANSWERS!!
What is the formula for specific degradation (D) in the Fournier index?
D = aC - b, where C = p²/P, and a and b are coefficients depending on the orographic coefficient.
What does the rainfall erosivity index (R) measure according to David and Collado (1987)?
It measures the number of erosion index units for a year based on daily rainfall totals greater than
25 mm.
What is the formula for calculating rainfall erosivity (R) according to David and Collado
(1987)?
R₁ = A • Π P₁, where A = 0.002 and m = 2.
What are the two classes of soil properties that influence soil erodibility (K)?
1. Properties affecting infiltration rate and permeability. 2. Properties resisting dispersion,
splashing, abrasion, and transport forces of rainfall and runoff.
What is the dispersion ratio as defined by Middleton (1930)?
It is the ratio of the weight of clay and silt in non-dispersed samples to the weight of clay and silt
in dispersed samples.
How is the erosion ratio defined in relation to the dispersion ratio?
The erosion ratio is the dispersion ratio divided by the ratio of colloid to moisture equivalent.
What indices did Lutz (1934) and Bouyoucos (1935) suggest for estimating soil erodibility
(K)?
They suggested that the clay ratio, or % sand and silt over % clay, is a good index of K.
What is the formula for calculating soil erodibility (K) according to Wischmeier and
Mannering (1969)?
, K = [(0.043 pH) + (0.62/OM) + (0.0082S) - (0.0062C)]Si.
What do the variables in the soil erodibility formula K represent?
K = soil erodibility factor, OM = organic matter content (%), S = % sand, C = clay ratio (% clay
/ (% silt + % sand)), Si = % silt / 100.
What is the consensus among researchers regarding the effect of slope on soil loss?
The only consensus is that E (total soil loss) is proportional to S (slope) raised to an exponent b,
expressed as E α Sb.
What does the equation Re = 0.1 + 0.21S^(4/3) represent?
It represents the relative soil loss (Re) to unity loss from a 3% slope, where S is the slope in
percentage.
What is the significance of the hydraulic radius in relation to slope length?
As slope length increases, the hydraulic radius increases with flow depth, leading to greater
detachment by runoff.
Why is sufficient data important for calculating erosion and sediment transport in the
Philippines?
Because the calculations of R for each storm and annual summation require a significant amount
of data that is often unavailable.
What is the relationship between rainfall distribution coefficient (C) and specific
degradation (D)?
There is a strong correlation where specific degradation (D) is influenced by the rainfall
distribution coefficient (C).
What does the variable P represent in the context of the rainfall erosivity index?
P represents the daily rainfall total greater than 25 mm.
What is the role of soil management in influencing soil erodibility (K)?
