Weak-settling attenuation of a sloping gravity current ($B^{1/3}\sim B_o^{1/3}-\frac{v_s}{3{\beta }_{\ast }E}\ln \left(1+\frac{E(x-x_0)}{h_0}\right)$)

For slowly depositing particles, $B_x=-v_{s}B/(uh)$ and local adjustment gives $u\sim {\beta }_{\ast }{B}^{1/3}$ with the constant-speed entraining gravity current on a slope coefficient. At leading order $h\sim h_0+E(x-x_0)$ and $B^{1/3}=B_o^{1/3}-[v_s/(3{\beta }_{\ast }E)]\ln [1+E(x-x_0)/h_0]$. Its validity requires settling slow compared with the current and, for small $E$, compared with entrainment.

Extrapolating the leading weak-settling attenuation of a sloping gravity current to zero flux gives $x_{\max }-x_0=(h_0/E)[\exp (3{\beta }_{\ast }E{B}_o^{1/3}/v_s)-1]$. Since speed tends to zero there, the weak-settling assumption fails in the terminal region; this is a formal leading-model estimate, not a uniformly accurate full-flow runout.