Index: DamEngine/trunk/src/Deltares.DamEngine.TestHelpers/Factories/FactoryForSurfaceLines.cs
===================================================================
diff -u -r5053 -r5238
--- DamEngine/trunk/src/Deltares.DamEngine.TestHelpers/Factories/FactoryForSurfaceLines.cs	(.../FactoryForSurfaceLines.cs)	(revision 5053)
+++ DamEngine/trunk/src/Deltares.DamEngine.TestHelpers/Factories/FactoryForSurfaceLines.cs	(.../FactoryForSurfaceLines.cs)	(revision 5238)
@@ -310,18 +310,18 @@
     }
 
     /// <summary>
-    /// Creates a horizontal surface line for benchmark 1.
+    /// Creates a horizontal surface line.
     /// </summary>
     /// <returns>surface line</returns>
-    public static SurfaceLine2 CreateHorizontalSurfaceLineForBenchmark1()
+    public static SurfaceLine2 CreateHorizontalSurfaceLine(double level)
     {
         var surfaceLine = new SurfaceLine2
         {
             Name = "HorizontalLine"
         };
 
-        surfaceLine.EnsurePointOfType(30, -0.2, CharacteristicPointType.DikeToeAtPolder);
-        surfaceLine.EnsurePointOfType(70, -0.2, CharacteristicPointType.SurfaceLevelInside);
+        surfaceLine.EnsurePointOfType(-10, level, CharacteristicPointType.SurfaceLevelOutside);
+        surfaceLine.EnsurePointOfType(10, level, CharacteristicPointType.SurfaceLevelInside);
 
         surfaceLine.Geometry.SyncCalcPoints();
         return surfaceLine;
Index: DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfileHelperTests.cs
===================================================================
diff -u
--- DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfileHelperTests.cs	(revision 0)
+++ DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfileHelperTests.cs	(revision 5238)
@@ -0,0 +1,108 @@
+// Copyright (C) Stichting Deltares 2024. All rights reserved.
+// 
+// This file is part of the Dam Engine.
+// 
+// The Dam Engine is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+// 
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+// 
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using Deltares.DamEngine.Data.Geotechnics;
+using Deltares.DamEngine.TestHelpers.Factories;
+using NUnit.Framework;
+
+namespace Deltares.DamEngine.Data.Tests.Geotechnics;
+
+[TestFixture]
+public class SoilProfileHelperTests
+{
+    public class GivenSurfaceLineInside1DProfile
+    {
+        private readonly SoilProfile1D soilProfile1D = CreateSoilProfile1D();
+        private readonly SurfaceLine2 surfaceLine = FactoryForSurfaceLines.CreateSurfaceLineTutorial1();
+
+        [Test]
+        public void WhenDetermining1DProfileAtDikeToeAtRiver_ThenExpectedLayersAboveAreRemoved()
+        {
+            SoilProfile1D soilProfile1D2 = SoilProfileHelper.DetermineForSurfaceLineCorrected1DProfileAtX(soilProfile1D, surfaceLine, 10, null);
+
+            Assert.That(soilProfile1D2.Layers, Has.Count.EqualTo(2));
+            Assert.Multiple(() =>
+            {
+                Assert.That(soilProfile1D2.Layers[0].TopLevel, Is.EqualTo(0));
+                Assert.That(soilProfile1D2.Layers[0].SoilName, Is.EqualTo("Layer 4"));
+                Assert.That(soilProfile1D2.Layers[1].TopLevel, Is.EqualTo(-3));
+                Assert.That(soilProfile1D2.Layers[1].SoilName, Is.EqualTo("Layer 5"));
+            });
+        }
+
+        [Test]
+        public void WhenDetermining1DProfileAtDikeTopAtPolder_ThenExpectedLayersAboveAreRemoved()
+        {
+            SoilProfile1D soilProfile1D2 = SoilProfileHelper.DetermineForSurfaceLineCorrected1DProfileAtX(soilProfile1D, surfaceLine, 40.5, null);
+
+            Assert.That(soilProfile1D2.Layers, Has.Count.EqualTo(4));
+            Assert.Multiple(() =>
+            {
+                Assert.That(soilProfile1D2.Layers[0].TopLevel, Is.EqualTo(5));
+                Assert.That(soilProfile1D2.Layers[0].SoilName, Is.EqualTo("Layer 2"));
+                Assert.That(soilProfile1D2.Layers[1].TopLevel, Is.EqualTo(4));
+                Assert.That(soilProfile1D2.Layers[1].SoilName, Is.EqualTo("Layer 3"));
+                Assert.That(soilProfile1D2.Layers[2].TopLevel, Is.EqualTo(2));
+                Assert.That(soilProfile1D2.Layers[2].SoilName, Is.EqualTo("Layer 4"));
+                Assert.That(soilProfile1D2.Layers[3].TopLevel, Is.EqualTo(-3));
+                Assert.That(soilProfile1D2.Layers[3].SoilName, Is.EqualTo("Layer 5"));
+            });
+        }
+    }
+
+    [Test]
+    public void GivenHorizontalSurfaceLineAbove1DProfile_WhenDetermining1DProfileAtMiddle_ThenExpectedLayerAddedAbove()
+    {
+        SoilProfile1D soilProfile1D = CreateSoilProfile1D();
+        SurfaceLine2 surfaceLine = FactoryForSurfaceLines.CreateHorizontalSurfaceLine(20);
+
+        SoilProfile1D soilProfile1D2 = SoilProfileHelper.DetermineForSurfaceLineCorrected1DProfileAtX(soilProfile1D, surfaceLine, 0, new Soil("Embankment"));
+
+        Assert.That(soilProfile1D2.Layers, Has.Count.EqualTo(6));
+        Assert.Multiple(() =>
+        {
+            Assert.That(soilProfile1D2.Layers[0].TopLevel, Is.EqualTo(20));
+            Assert.That(soilProfile1D2.Layers[0].SoilName, Is.EqualTo("Embankment"));
+            Assert.That(soilProfile1D2.Layers[1].TopLevel, Is.EqualTo(10));
+            Assert.That(soilProfile1D2.Layers[1].SoilName, Is.EqualTo("Layer 1"));
+            Assert.That(soilProfile1D2.Layers[2].TopLevel, Is.EqualTo(6));
+            Assert.That(soilProfile1D2.Layers[2].SoilName, Is.EqualTo("Layer 2"));
+            Assert.That(soilProfile1D2.Layers[3].TopLevel, Is.EqualTo(4));
+            Assert.That(soilProfile1D2.Layers[3].SoilName, Is.EqualTo("Layer 3"));
+            Assert.That(soilProfile1D2.Layers[4].TopLevel, Is.EqualTo(2));
+            Assert.That(soilProfile1D2.Layers[4].SoilName, Is.EqualTo("Layer 4"));
+            Assert.That(soilProfile1D2.Layers[5].TopLevel, Is.EqualTo(-3));
+            Assert.That(soilProfile1D2.Layers[5].SoilName, Is.EqualTo("Layer 5"));
+        });
+    }
+
+    private static SoilProfile1D CreateSoilProfile1D()
+    {
+        var soilProfile1D = new SoilProfile1D();
+        soilProfile1D.Layers.Add(new SoilLayer1D(new Soil("Layer 1"), 10));
+        soilProfile1D.Layers.Add(new SoilLayer1D(new Soil("Layer 2"), 6));
+        soilProfile1D.Layers.Add(new SoilLayer1D(new Soil("Layer 3"), 4));
+        soilProfile1D.Layers.Add(new SoilLayer1D(new Soil("Layer 4"), 2));
+        soilProfile1D.Layers.Add(new SoilLayer1D(new Soil("Layer 5"), -3));
+            
+        return soilProfile1D;
+    }
+}
\ No newline at end of file