Index: Ringtoets/GrassCoverErosionInwards/src/Ringtoets.GrassCoverErosionInwards.Service/GrassCoverErosionInwardsCalculationService.cs
===================================================================
diff -u -rc73100fd8408a2865d6fb32bd17608502686b605 -r04d96e936610eab56e9ddc09c055526efe9b9652
--- Ringtoets/GrassCoverErosionInwards/src/Ringtoets.GrassCoverErosionInwards.Service/GrassCoverErosionInwardsCalculationService.cs	(.../GrassCoverErosionInwardsCalculationService.cs)	(revision c73100fd8408a2865d6fb32bd17608502686b605)
+++ Ringtoets/GrassCoverErosionInwards/src/Ringtoets.GrassCoverErosionInwards.Service/GrassCoverErosionInwardsCalculationService.cs	(.../GrassCoverErosionInwardsCalculationService.cs)	(revision 04d96e936610eab56e9ddc09c055526efe9b9652)
@@ -100,19 +100,19 @@
             return input.ForeshoreGeometry.Select(c => new HydraRingForelandPoint(c.X, c.Y));
         }
 
-        private static IEnumerable<HydraRingRoughnessProfilePoint> ParseProfilePoints(IEnumerable<RoughnessPoint> roughnessProfilePoints)
+        private static IEnumerable<HydraRingRoughnessProfilePoint> ParseProfilePoints(RoughnessPoint[] roughnessProfilePoints)
         {
-            for (var i = 0; i < roughnessProfilePoints.Count(); i++)
+            for (var i = 0; i < roughnessProfilePoints.Length; i++)
             {
-                var roughnessProfilePoint = roughnessProfilePoints.ElementAt(i);
+                var roughnessProfilePoint = roughnessProfilePoints[i];
 
                 if (i == 0)
                 {
                     yield return new HydraRingRoughnessProfilePoint(roughnessProfilePoint.Point.X, roughnessProfilePoint.Point.Y, 1.0);
                 }
                 else
                 {
-                    var precedingRoughnessProfilePoint = roughnessProfilePoints.ElementAt(i - 1);
+                    var precedingRoughnessProfilePoint = roughnessProfilePoints[i - 1];
 
                     yield return new HydraRingRoughnessProfilePoint(roughnessProfilePoint.Point.X, roughnessProfilePoint.Point.Y, precedingRoughnessProfilePoint.Roughness);
                 }