Stop ListContourPlot from interpolating beyond the data points

Question

I am using listcontourplot to show my 3D data points but It is interpolating between faraway points and it is changing the outline of the shape.
this is what I want to see:

and this is what I have:

You can see the sharp cells around the area. and this is my code:

m = Min[data[[All, 3]]]
M = Max[data[[All, 3]]]
lb = 15
ub = 400
nc = 16;
depth = -15;
l2 = {{12, depth}, {12, 0}};
l3 = {{24, depth}, {24, 0}};

ListContourPlot[data,
 PlotRange -> {Automatic, {0, depth}, {m, M}},
 PlotLegends -> 
  Placed[BarLegend[{Automatic, {lb, ub}}, LegendMarkerSize -> 500, 
    LegendLabel -> Placed["\[CapitalOmega].m", Right], 
    LabelStyle -> {Black, 14}, "LabelingFunction" -> (Round[#] &)], 
   Bottom],
 ColorFunctionScaling -> False,
 ContourShading -> Hue /@ Reverse[Subdivide[.67, nc - 1]],
 ImageSize -> 1200,
 ContourStyle -> None,
 Contours -> Table[lb*(ub/lb)^(n/nc), {n, 1, nc - 1}],
 PlotRangePadding -> None,
 FrameLabel -> {"Distance (m)", "Depth (m)", None, "Elevation (ft)"},
 LabelStyle -> {Black, 14},
 FrameTicks -> {{All, 
    Table[{-3.05 n, 262 - 10 n}, {n, 0, 9, 1}]}, {Table[
     n, {n, 0, 160, 10}], None}},
 AspectRatio -> .3,
 Epilog -> {Black, Dashed, Thick, Line[l2], 
   Style[Text["Line 2", {l2[[1, 1]] - 2, depth + 1}], 14], Line[l3], 
   Style[Text["Line3", {l3[[1, 1]] - 2, depth + 1}], 14]},
 Mesh -> All
 ] 

Answer 1

You need to use data[[All, {1, 2}]] to define a RegionFunction:

data = Join @@ Table[{x, y, x Sin[x y/111 + 1/14 Exp[x/115]]}, {x, Range[0, 40]}, {y, 0, If[x > 20, x, 20]}];
ListContourPlot[data] (*Same problem as yours*)
ListContourPlot[data, RegionFunction -> Function[{x, y, z}, If[x > 20, y < x, y < 20]]]

Answer 2

I think this link shows a general case: ListContourPlot interpolation screws up on concave set of data Using regionfunction and interpolation to show the data points below their boundary. enter link description here