Index: DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/GeometrySurface.cs
===================================================================
diff -u -r5565 -r5617
--- DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/GeometrySurface.cs	(.../GeometrySurface.cs)	(revision 5565)
+++ DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/GeometrySurface.cs	(.../GeometrySurface.cs)	(revision 5617)
@@ -96,12 +96,17 @@
     /// </summary>
     public void AddInnerLoop(GeometryLoop aLoop)
     {
-        if (!InnerLoops.Contains(aLoop))
+        if (!InnerLoops.Contains(aLoop) && !HasIdeneticalInnerLoop(aLoop))
         {
             InnerLoops.Add(aLoop);
         }
     }
 
+    private bool HasIdeneticalInnerLoop(GeometryLoop loop)
+    {
+        return InnerLoops.Any(innerLoop => innerLoop.HasSameCurvesByReference(loop));
+    }
+    
     /// <summary>
     /// Remove all inner loops from the surface whilst updating the previous inner loops list.
     /// </summary>