How can I plot 2D streamlines on top of a surf plot?

I have a 3D surf plot of the variable 'conc' - a matrix of size (Nx x Ny) which I am plotting as surf(x, y, conc') and then using view(2) to view in 2D top down. I also have matrices uX and uY also of size (Nx x Ny). I make 2D streamlines/streamslices of these in the standard manner and then wish to plot these as an overlay on the surf figure, so that the streamlines appear on top of any surf.

The issue is that the surf figure has z values associated with conc whereas the streamlines are entirely 2D so always render underneath. Does anyone know how I may fix this?

Code is below. I use streamslice here but I have also tried with streamlines (note that streamslice is preferred since I want directional arrows).

% conc plot first
figure(1);
surf(x,y,conc');
daspect([1 1 1]);
shading interp;
xlabel("$X$");
ylabel("$Y$");
view(2);
c = colorbar;
clim([1.0 1.2]);

% now streamlines
[X, Y] = meshgrid(x, y);
hold on
h=streamslice(X, Y, uX', uY');

Answer 1

[KSSV]

% conc plot first
[X,Y,Z] = peaks(100) ; 
[uX,uY] = gradient(Z) ; 

figure(1);
surf(X,Y,Z);
daspect([1 1 1]);
shading interp;
xlabel("$X$");
ylabel("$Y$");
view(2);
c = colorbar;
% clim([1.0 1.2]);

% now streamlines

hold on
h=streamslice(X, Y,uX, uY);
set(h,'Color','k');
for i=1:length(h)
    zi = interp2(X,Y,Z,h(i).XData, h(i).YData);
    h(i).ZData = zi;
end

[Arthur]

This works - thanks so much!!