Topography Grid Update Steps

[1] Advect Eulerian topography marker chain nodes $(x_t, y_t)$ using 4th order Runge-Kutta scheme and the current velocity field $v_{x(i,j)_{v_x}}$ and $v_{y(i,j)_{v_y}}$ to obtain $(x_t', y_t')$.

[2] Interpolate advected topography nodes $(x_{t,adv}, y_{t,adv})$ to the Eulerian topography grid the to obtain new y-coordinates $y_t^{new}$ for the Eulerian grid at x-coordinates $x_t$.

[3] Update topography marker chain nodes $(x_t, y_t)$ by setting $y_t$ equal to $y_t^{new}$.