Index: Ringtoets/Common/src/Ringtoets.Common.IO/FileImporters/StructuresImporter.cs
===================================================================
diff -u -r56a1b0ad79756583461f17301d0edcd79a1d0de4 -r250f2f821d2540a5c562d5fa9ccaab669dacb24b
--- Ringtoets/Common/src/Ringtoets.Common.IO/FileImporters/StructuresImporter.cs	(.../StructuresImporter.cs)	(revision 56a1b0ad79756583461f17301d0edcd79a1d0de4)
+++ Ringtoets/Common/src/Ringtoets.Common.IO/FileImporters/StructuresImporter.cs	(.../StructuresImporter.cs)	(revision 250f2f821d2540a5c562d5fa9ccaab669dacb24b)
@@ -41,6 +41,7 @@
     /// Abstract class for structure importers, providing an implementation of importing point shapefiles 
     /// containing structure locations and csv files containing structure schematizations.
     /// </summary>
+    /// <typeparam name="T">Object type that is the target for this importer.</typeparam>
     public abstract class StructuresImporter<T> : FileImporterBase<T>
     {
         private readonly ILog log = LogManager.GetLogger(typeof(StructuresImporter<T>));
Index: Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.IO/HeightStructuresImporter.cs
===================================================================
diff -u -r58c471864c590aff4b609e7c2df36a220bf390b1 -r250f2f821d2540a5c562d5fa9ccaab669dacb24b
--- Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.IO/HeightStructuresImporter.cs	(.../HeightStructuresImporter.cs)	(revision 58c471864c590aff4b609e7c2df36a220bf390b1)
+++ Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.IO/HeightStructuresImporter.cs	(.../HeightStructuresImporter.cs)	(revision 250f2f821d2540a5c562d5fa9ccaab669dacb24b)
@@ -37,24 +37,37 @@
     /// </summary>
     public class HeightStructuresImporter : StructuresImporter<StructureCollection<HeightStructure>>
     {
+        private readonly IStructureUpdateStrategy<HeightStructure> structureUpdateStrategy;
+
         /// <summary>
         /// Creates a new instance of <see cref="HeightStructuresImporter"/>.
         /// </summary>
         /// <param name="importTarget">The height structures to import on.</param>
         /// <param name="referenceLine">The reference line used to check if the <see cref="HeightStructure"/>
         /// objects found in the file are intersecting it.</param>
+        /// <param name="structureUpdateStrategy">The strategy to update the structures with imported data.</param>
         /// <param name="filePath">The path to the file to import from.</param>
-        /// <exception cref="ArgumentNullException">Thrown when <paramref name="referenceLine"/>, 
-        /// <paramref name="filePath"/> or <paramref name="importTarget"/> is <c>null</c>.</exception>
-        public HeightStructuresImporter(StructureCollection<HeightStructure> importTarget,
-                                        ReferenceLine referenceLine, string filePath)
-            : base(importTarget, referenceLine, filePath) {}
+        /// <exception cref="ArgumentNullException">Thrown when any of the input parameters is <c>null</c>.</exception>
+        public HeightStructuresImporter(StructureCollection<HeightStructure> importTarget, ReferenceLine referenceLine,
+                                        IStructureUpdateStrategy<HeightStructure> structureUpdateStrategy,
+                                        string filePath)
+            : base(importTarget, referenceLine, filePath)
+        {
+            if (structureUpdateStrategy == null)
+            {
+                throw new ArgumentNullException(nameof(structureUpdateStrategy));
+            }
 
+            this.structureUpdateStrategy = structureUpdateStrategy;
+        }
+
         protected override void CreateSpecificStructures(ICollection<StructureLocation> structureLocations,
                                                          Dictionary<string, List<StructuresParameterRow>> groupedStructureParameterRows)
         {
-            ImportTarget.AddRange(CreateHeightStructures(structureLocations.ToList(), groupedStructureParameterRows).ToArray(),
-                                  FilePath);
+            structureUpdateStrategy.UpdateStructuresWithImportedData(ImportTarget,
+                                                                     CreateHeightStructures(structureLocations.ToList(),
+                                                                                            groupedStructureParameterRows).ToArray(),
+                                                                     FilePath);
         }
 
         private IEnumerable<HeightStructure> CreateHeightStructures(IEnumerable<StructureLocation> structureLocations,
Index: Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/HeightStructuresPlugin.cs
===================================================================
diff -u -rc10213be206d81cd8618603d9e526f18f070211b -r250f2f821d2540a5c562d5fa9ccaab669dacb24b
--- Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/HeightStructuresPlugin.cs	(.../HeightStructuresPlugin.cs)	(revision c10213be206d81cd8618603d9e526f18f070211b)
+++ Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/HeightStructuresPlugin.cs	(.../HeightStructuresPlugin.cs)	(revision 250f2f821d2540a5c562d5fa9ccaab669dacb24b)
@@ -51,6 +51,7 @@
 using Ringtoets.HeightStructures.Forms.Views;
 using Ringtoets.HeightStructures.IO;
 using Ringtoets.HeightStructures.IO.Configurations;
+using Ringtoets.HeightStructures.Plugin.FileImporters;
 using Ringtoets.HeightStructures.Service;
 using RingtoetsCommonFormsResources = Ringtoets.Common.Forms.Properties.Resources;
 using RingtoetsCommonDataResources = Ringtoets.Common.Data.Properties.Resources;
@@ -90,6 +91,7 @@
             {
                 CreateFileImporter = (context, filePath) => new HeightStructuresImporter(context.WrappedData,
                                                                                          context.AssessmentSection.ReferenceLine,
+                                                                                         new HeightStructureReplaceDataStrategy(context.FailureMechanism),
                                                                                          filePath),
                 Name = RingtoetsCommonFormsResources.StructuresImporter_DisplayName,
                 Category = RingtoetsCommonFormsResources.Ringtoets_Category,
Index: Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.IO.Test/HeightStructuresImporterTest.cs
===================================================================
diff -u -r58c471864c590aff4b609e7c2df36a220bf390b1 -r250f2f821d2540a5c562d5fa9ccaab669dacb24b
--- Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.IO.Test/HeightStructuresImporterTest.cs	(.../HeightStructuresImporterTest.cs)	(revision 58c471864c590aff4b609e7c2df36a220bf390b1)
+++ Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.IO.Test/HeightStructuresImporterTest.cs	(.../HeightStructuresImporterTest.cs)	(revision 250f2f821d2540a5c562d5fa9ccaab669dacb24b)
@@ -31,6 +31,7 @@
 using Ringtoets.Common.Data.TestUtil;
 using Ringtoets.Common.IO.FileImporters;
 using Ringtoets.HeightStructures.Data;
+using Ringtoets.HeightStructures.Plugin.FileImporters;
 
 namespace Ringtoets.HeightStructures.IO.Test
 {
@@ -42,10 +43,26 @@
         private readonly string testFilePath = string.Empty;
 
         [Test]
+        public void Constructor_StructureUpdateStrategyNull_ThrowsArgumentNullException()
+        {
+            // Call
+            TestDelegate call = () => new HeightStructuresImporter(testImportTarget, testReferenceLine,
+                                                                   null, testFilePath);
+
+            // Assert
+            string paramName = Assert.Throws<ArgumentNullException>(call).ParamName;
+            Assert.AreEqual("structureUpdateStrategy", paramName);
+        }
+
+        [Test]
         public void Constructor_Always_ExpectedValues()
         {
+            // Setup
+            var replaceDataStrategy = new HeightStructureReplaceDataStrategy(new HeightStructuresFailureMechanism());
+
             // Call
-            var importer = new HeightStructuresImporter(testImportTarget, testReferenceLine, testFilePath);
+            var importer = new HeightStructuresImporter(testImportTarget, testReferenceLine,
+                                                        replaceDataStrategy, testFilePath);
 
             // Assert
             Assert.IsInstanceOf<StructuresImporter<StructureCollection<HeightStructure>>>(importer);
@@ -56,12 +73,15 @@
         {
             // Setup
             string filePath = TestHelper.GetTestDataPath(TestDataPath.Ringtoets.Common.IO,
-                                                         Path.Combine("Structures", "CorrectFiles", "Kunstwerken.shp"));
+                                                         Path.Combine("Structures", "CorrectFiles",
+                                                                      "Kunstwerken.shp"));
 
             ReferenceLine referenceLine = CreateReferenceLine();
+            var failureMechanism = new HeightStructuresFailureMechanism();
+            var replaceDataStrategy = new HeightStructureReplaceDataStrategy(failureMechanism);
 
-            var importTarget = new StructureCollection<HeightStructure>();
-            var structuresImporter = new HeightStructuresImporter(importTarget, referenceLine, filePath);
+            var structuresImporter = new HeightStructuresImporter(failureMechanism.HeightStructures,
+                                                                  referenceLine, replaceDataStrategy, filePath);
 
             // Call
             var importResult = false;
@@ -83,22 +103,26 @@
             };
             TestHelper.AssertLogMessagesAreGenerated(call, expectedMessages);
             Assert.IsTrue(importResult);
-            Assert.AreEqual(1, importTarget.Count);
-            Assert.AreEqual(filePath, importTarget.SourcePath);
+            Assert.AreEqual(1, failureMechanism.HeightStructures.Count);
+            Assert.AreEqual(filePath, failureMechanism.HeightStructures.SourcePath);
         }
 
         [Test]
         public void Import_ValidFileWithConversionsBetweenVarianceTypes_WarnUserAboutConversion()
         {
             // Setup
             string filePath = TestHelper.GetTestDataPath(TestDataPath.Ringtoets.HeightStructures.IO,
-                                                         Path.Combine("HeightStructuresVarianceConvert", "StructureNeedVarianceValueConversion.shp"));
+                                                         Path.Combine("HeightStructuresVarianceConvert",
+                                                                      "StructureNeedVarianceValueConversion.shp"));
 
             ReferenceLine referenceLine = CreateReferenceLine();
 
-            var importTarget = new StructureCollection<HeightStructure>();
-            var structuresImporter = new HeightStructuresImporter(importTarget, referenceLine, filePath);
+            var failureMechanism = new HeightStructuresFailureMechanism();
+            var replaceDataStrategy = new HeightStructureReplaceDataStrategy(failureMechanism);
 
+            var structuresImporter = new HeightStructuresImporter(failureMechanism.HeightStructures,
+                                                                  referenceLine, replaceDataStrategy, filePath);
+
             // Call
             var importResult = false;
             Action call = () => importResult = structuresImporter.Import();
@@ -115,15 +139,15 @@
             };
             TestHelper.AssertLogMessagesAreGenerated(call, expectedMessages);
             Assert.IsTrue(importResult);
-            Assert.AreEqual(1, importTarget.Count);
-            HeightStructure structure = importTarget[0];
+            Assert.AreEqual(1, failureMechanism.HeightStructures.Count);
+            HeightStructure structure = failureMechanism.HeightStructures[0];
             Assert.AreEqual(0.12, structure.LevelCrestStructure.StandardDeviation.Value);
             Assert.AreEqual(0.24, structure.FlowWidthAtBottomProtection.StandardDeviation.Value);
             Assert.AreEqual(1.0, structure.CriticalOvertoppingDischarge.CoefficientOfVariation.Value);
             Assert.AreEqual(0.97, structure.WidthFlowApertures.StandardDeviation.Value);
             Assert.AreEqual(1.84, structure.StorageStructureArea.CoefficientOfVariation.Value);
             Assert.AreEqual(2.18, structure.AllowedLevelIncreaseStorage.StandardDeviation.Value);
-            Assert.AreEqual(filePath, importTarget.SourcePath);
+            Assert.AreEqual(filePath, failureMechanism.HeightStructures.SourcePath);
         }
 
         [Test]
@@ -132,13 +156,15 @@
         {
             // Setup
             string filePath = TestHelper.GetTestDataPath(TestDataPath.Ringtoets.Common.IO,
-                                                         Path.Combine("Structures", "CorrectShpIncompleteCsv", "Kunstwerken.shp"));
+                                                         Path.Combine("Structures", "CorrectShpIncompleteCsv",
+                                                                      "Kunstwerken.shp"));
 
             ReferenceLine referenceLine = CreateReferenceLine();
+            var failureMechanism = new HeightStructuresFailureMechanism();
+            var replaceDataStrategy = new HeightStructureReplaceDataStrategy(failureMechanism);
+            var structuresImporter = new HeightStructuresImporter(failureMechanism.HeightStructures,
+                                                                  referenceLine, replaceDataStrategy, filePath);
 
-            var importTarget = new StructureCollection<HeightStructure>();
-            var structuresImporter = new HeightStructuresImporter(importTarget, referenceLine, filePath);
-
             // Call
             var importResult = false;
             Action call = () => importResult = structuresImporter.Import();
@@ -165,21 +191,24 @@
             };
             TestHelper.AssertLogMessagesAreGenerated(call, expectedMessages);
             Assert.IsTrue(importResult);
-            Assert.AreEqual(0, importTarget.Count);
-            Assert.AreEqual(filePath, importTarget.SourcePath);
+            Assert.AreEqual(0, failureMechanism.HeightStructures.Count);
+            Assert.AreEqual(filePath, failureMechanism.HeightStructures.SourcePath);
         }
 
         [Test]
         public void Import_MissingParameters_LogWarningAndContinueImportWithDefaultValues()
         {
             // Setup
             string filePath = TestHelper.GetTestDataPath(TestDataPath.Ringtoets.HeightStructures.IO,
-                                                         Path.Combine(nameof(HeightStructuresImporter), "Kunstwerken.shp"));
+                                                         Path.Combine(nameof(HeightStructuresImporter),
+                                                                      "Kunstwerken.shp"));
 
             ReferenceLine referenceLine = CreateReferenceLine();
 
-            var importTarget = new StructureCollection<HeightStructure>();
-            var structuresImporter = new HeightStructuresImporter(importTarget, referenceLine, filePath);
+            var failureMechanism = new HeightStructuresFailureMechanism();
+            var replaceDataStrategy = new HeightStructureReplaceDataStrategy(failureMechanism);
+            var structuresImporter = new HeightStructuresImporter(failureMechanism.HeightStructures,
+                                                                  referenceLine, replaceDataStrategy, filePath);
 
             // Call
             var importResult = false;
@@ -199,8 +228,8 @@
                 // Don't care about the other message.
             });
             Assert.IsTrue(importResult);
-            Assert.AreEqual(1, importTarget.Count);
-            HeightStructure importedStructure = importTarget.First();
+            Assert.AreEqual(1, failureMechanism.HeightStructures.Count);
+            HeightStructure importedStructure = failureMechanism.HeightStructures.First();
             var defaultStructure = new HeightStructure(new HeightStructure.ConstructionProperties
             {
                 Name = "test",
@@ -210,15 +239,16 @@
             Assert.AreEqual(defaultStructure.StructureNormalOrientation, importedStructure.StructureNormalOrientation);
             DistributionAssert.AreEqual(defaultStructure.FlowWidthAtBottomProtection, importedStructure.FlowWidthAtBottomProtection);
             Assert.AreEqual(defaultStructure.FailureProbabilityStructureWithErosion, importedStructure.FailureProbabilityStructureWithErosion);
-            Assert.AreEqual(filePath, importTarget.SourcePath);
+            Assert.AreEqual(filePath, failureMechanism.HeightStructures.SourcePath);
         }
 
         [Test]
         public void Import_ParameterIdsWithVaryingCase_TrueAndImportTargetUpdated()
         {
             // Setup
             string filePath = TestHelper.GetTestDataPath(TestDataPath.Ringtoets.Common.IO,
-                                                         Path.Combine("Structures", "CorrectShpRandomCaseHeaderCsv", "Kunstwerken.shp"));
+                                                         Path.Combine("Structures", "CorrectShpRandomCaseHeaderCsv",
+                                                                      "Kunstwerken.shp"));
 
             var referencePoints = new List<Point2D>
             {
@@ -229,16 +259,19 @@
             };
             var referenceLine = new ReferenceLine();
             referenceLine.SetGeometry(referencePoints);
-            var importTarget = new StructureCollection<HeightStructure>();
-            var structuresImporter = new HeightStructuresImporter(importTarget, referenceLine, filePath);
 
+            var failureMechanism = new HeightStructuresFailureMechanism();
+            var replaceDataStrategy = new HeightStructureReplaceDataStrategy(failureMechanism);
+            var structuresImporter = new HeightStructuresImporter(failureMechanism.HeightStructures,
+                                                                  referenceLine, replaceDataStrategy, filePath);
+
             // Call
             bool importResult = structuresImporter.Import();
 
             // Assert
             Assert.IsTrue(importResult);
-            Assert.AreEqual(4, importTarget.Count);
-            Assert.AreEqual(filePath, importTarget.SourcePath);
+            Assert.AreEqual(4, failureMechanism.HeightStructures.Count);
+            Assert.AreEqual(filePath, failureMechanism.HeightStructures.SourcePath);
         }
 
         private static ReferenceLine CreateReferenceLine()
Index: Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.IO.Test/Ringtoets.HeightStructures.IO.Test.csproj
===================================================================
diff -u -r8aeff3f1153aaac2b2980ca207e298b6d764947b -r250f2f821d2540a5c562d5fa9ccaab669dacb24b
--- Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.IO.Test/Ringtoets.HeightStructures.IO.Test.csproj	(.../Ringtoets.HeightStructures.IO.Test.csproj)	(revision 8aeff3f1153aaac2b2980ca207e298b6d764947b)
+++ Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.IO.Test/Ringtoets.HeightStructures.IO.Test.csproj	(.../Ringtoets.HeightStructures.IO.Test.csproj)	(revision 250f2f821d2540a5c562d5fa9ccaab669dacb24b)
@@ -98,6 +98,10 @@
       <Project>{D63FCFEC-34E8-4C68-8B4F-99338D2447AC}</Project>
       <Name>Ringtoets.HeightStructures.IO</Name>
     </ProjectReference>
+    <ProjectReference Include="..\..\src\Ringtoets.HeightStructures.Plugin\Ringtoets.HeightStructures.Plugin.csproj">
+      <Project>{9AF85B2B-8D78-43C5-9542-FBB3A14EAB36}</Project>
+      <Name>Ringtoets.HeightStructures.Plugin</Name>
+    </ProjectReference>
     <ProjectReference Include="..\Ringtoets.HeightStructures.Data.TestUtil\Ringtoets.HeightStructures.Data.TestUtil.csproj">
       <Project>{F67E8AE8-1FF0-4680-9817-99E025CD9FF6}</Project>
       <Name>Ringtoets.HeightStructures.Data.TestUtil</Name>
Index: Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Integration.Test/HeightStructuresScenariosViewIntegrationTest.cs
===================================================================
diff -u -r20e9bfea15dfe132ee137283a9f24bc4c413ce4a -r250f2f821d2540a5c562d5fa9ccaab669dacb24b
--- Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Integration.Test/HeightStructuresScenariosViewIntegrationTest.cs	(.../HeightStructuresScenariosViewIntegrationTest.cs)	(revision 20e9bfea15dfe132ee137283a9f24bc4c413ce4a)
+++ Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Integration.Test/HeightStructuresScenariosViewIntegrationTest.cs	(.../HeightStructuresScenariosViewIntegrationTest.cs)	(revision 250f2f821d2540a5c562d5fa9ccaab669dacb24b)
@@ -34,6 +34,7 @@
 using Ringtoets.HeightStructures.Data;
 using Ringtoets.HeightStructures.Forms.Views;
 using Ringtoets.HeightStructures.IO;
+using Ringtoets.HeightStructures.Plugin.FileImporters;
 using Ringtoets.Integration.Data;
 using Ringtoets.Integration.TestUtils;
 
@@ -93,10 +94,11 @@
             {
                 var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
                 DataImportHelper.ImportReferenceLine(assessmentSection);
-                IFailureMechanism failureMechanism = assessmentSection.HeightStructures;
+                HeightStructuresFailureMechanism failureMechanism = assessmentSection.HeightStructures;
                 DataImportHelper.ImportFailureMechanismSections(assessmentSection, failureMechanism);
                 new HeightStructuresImporter(assessmentSection.HeightStructures.HeightStructures,
                                              assessmentSection.ReferenceLine,
+                                             new HeightStructureReplaceDataStrategy(failureMechanism),
                                              filePath)
                     .Import();
 
@@ -141,10 +143,11 @@
             {
                 var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
                 DataImportHelper.ImportReferenceLine(assessmentSection);
-                IFailureMechanism failureMechanism = assessmentSection.HeightStructures;
+                HeightStructuresFailureMechanism failureMechanism = assessmentSection.HeightStructures;
                 DataImportHelper.ImportFailureMechanismSections(assessmentSection, failureMechanism);
                 new HeightStructuresImporter(assessmentSection.HeightStructures.HeightStructures,
                                              assessmentSection.ReferenceLine,
+                                             new HeightStructureReplaceDataStrategy(failureMechanism),
                                              filePath)
                     .Import();
 
@@ -195,10 +198,11 @@
             {
                 var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
                 DataImportHelper.ImportReferenceLine(assessmentSection);
-                IFailureMechanism failureMechanism = assessmentSection.HeightStructures;
+                HeightStructuresFailureMechanism failureMechanism = assessmentSection.HeightStructures;
                 DataImportHelper.ImportFailureMechanismSections(assessmentSection, failureMechanism);
                 new HeightStructuresImporter(assessmentSection.HeightStructures.HeightStructures,
                                              assessmentSection.ReferenceLine,
+                                             new HeightStructureReplaceDataStrategy(failureMechanism),
                                              filePath)
                     .Import();
 
Index: Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Integration.Test/Ringtoets.HeightStructures.Integration.Test.csproj
===================================================================
diff -u -r08b3bcba439831d547684b194ecdf903f2519700 -r250f2f821d2540a5c562d5fa9ccaab669dacb24b
--- Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Integration.Test/Ringtoets.HeightStructures.Integration.Test.csproj	(.../Ringtoets.HeightStructures.Integration.Test.csproj)	(revision 08b3bcba439831d547684b194ecdf903f2519700)
+++ Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Integration.Test/Ringtoets.HeightStructures.Integration.Test.csproj	(.../Ringtoets.HeightStructures.Integration.Test.csproj)	(revision 250f2f821d2540a5c562d5fa9ccaab669dacb24b)
@@ -119,6 +119,10 @@
       <Project>{D63FCFEC-34E8-4C68-8B4F-99338D2447AC}</Project>
       <Name>Ringtoets.HeightStructures.IO</Name>
     </ProjectReference>
+    <ProjectReference Include="..\..\src\Ringtoets.HeightStructures.Plugin\Ringtoets.HeightStructures.Plugin.csproj">
+      <Project>{9AF85B2B-8D78-43C5-9542-FBB3A14EAB36}</Project>
+      <Name>Ringtoets.HeightStructures.Plugin</Name>
+    </ProjectReference>
     <ProjectReference Include="..\..\src\Ringtoets.HeightStructures.Service\Ringtoets.HeightStructures.Service.csproj">
       <Project>{20DD96D3-001E-407A-AE2E-432887088F1F}</Project>
       <Name>Ringtoets.HeightStructures.Service</Name>