Compute long-term channel incision according to a stream power-based instantaneous incision law and an inverse gamma distribution for discharge

This function is actually solving equation 10 from Dibiase and Whipple (2011)

I_long_term(k, ks, Psi, K, n, gamma)

Arguments

k

Variability parameter of the inverse gamma distribution for discharge
ks

Channel steepness index
Psi

Incision threshold
K

erodibility
n

slope exponent of the stream power law
gamma

discharge exponent

Value

Long-term incision value (m/s)