g[x_,y_]=30Exp[-y^2] FresnelC[x]FresnelC[y];

gradg[x_,y_]=Grad[g[x,y],{x,y}];

Show[ContourPlot[g[x,y],{x,0.8,2.5},{y,0,1.7},ContourLabels->True,Contours->13],ContourPlot[g[x,y]==g[1.5,0.5],{x,0.8,2.5},{y,0,1.7},ContourStyle->{Blue,Thick}],Graphics[{PointSize[Large],Blue,Thick,Point[{1.5,0.5}],Arrow[{{1.5,0.5},{1.5,0.5}+0.01*gradg[1.5,0.5]}]}],StreamPlot[gradg[x,y],{x,0.8,2.5},{y,0,1.7}]]

Table[{k 0.5},{k,1,9}]

Show[Plot3D[{-4,30 Exp[-y^2] FresnelC[x]FresnelC[y]},{x,0.8,2.5},{y,0,1.7},PlotStyle->Opacity[0.4], MeshFunctions->{g[#1,#2]&,g[#1,#2]&},Mesh->{{{g[1.5,0.5]}},Table[{k 0.5},{k,1,18}]},MeshStyle->{{Thick,Red},{Black}},PlotPoints->50,AspectRatio->Automatic],Graphics3D[{{Thick,Black,Dashed,Line[{{1.5,0.5,-4},{1.5,0.5,g[1.5,0.5]}}]},{PointSize[Large],Thick,Black,Point[{{1.5,0.5,-4},{1.5,0.5,g[1.5,0.5]}}]}}],ParametricPlot3D[{{1.5,0.5,-4}+0.01t Join[gradg[1.5,0.5],{-4}]},{t,-2,2},PlotStyle->{Blue,Thick}]]