Create perpendicular lines to Contour lines

I am new in Paraview. It has helped me a lot with my visualizations and I think it is a very nice software. Now, I am facing a problem: I have a 3D hydrogeological model and I need to make a slice in order to get Contour Lines of hydraulic head. I already created those files, but now I need to create another file with arrows perpendicular to the Contour lines of hydraulic head in order to simulate the flow direction. I cannot use the Stream Tracer tool in the Slice file, because it results in discontinuous flow lines (probably because the velocity field is calculated at the center of each tetrahedra?? or maybe because Vx, Vy and Vz are not equal to zero??). Do you know how I can get what I need?? Thank you very much in advance!