diff --git a/OpenSim/Region/Terrain.BasicTerrain/libTerrainBSD/Channel/Manipulators/HydraulicErosion.cs b/OpenSim/Region/Terrain.BasicTerrain/libTerrainBSD/Channel/Manipulators/HydraulicErosion.cs
index 0cec05d3dd..e3463c1e65 100644
--- a/OpenSim/Region/Terrain.BasicTerrain/libTerrainBSD/Channel/Manipulators/HydraulicErosion.cs
+++ b/OpenSim/Region/Terrain.BasicTerrain/libTerrainBSD/Channel/Manipulators/HydraulicErosion.cs
@@ -1 +1,144 @@
-/* Needs BSD rewrite */
\ No newline at end of file
+/*
+* Copyright (c) Contributors, http://www.openmetaverse.org/
+* See CONTRIBUTORS.TXT for a full list of copyright holders.
+*
+* Redistribution and use in source and binary forms, with or without
+* modification, are permitted provided that the following conditions are met:
+*     * Redistributions of source code must retain the above copyright
+*       notice, this list of conditions and the following disclaimer.
+*     * Redistributions in binary form must reproduce the above copyright
+*       notice, this list of conditions and the following disclaimer in the
+*       documentation and/or other materials provided with the distribution.
+*     * Neither the name of the OpenSim Project nor the
+*       names of its contributors may be used to endorse or promote products
+*       derived from this software without specific prior written permission.
+*
+* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS AND ANY
+* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+* 
+*/
+
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace libTerrain
+{
+    partial class Channel
+    {
+        public void hydraulicErosion(Channel rain, double evaporation, double solubility, int frequency, int rounds)
+        {
+            Channel water = new Channel(w, h);
+            Channel sediment = new Channel(w, h);
+            Channel terrain = this;
+            Channel waterFlow = new Channel(w, h);
+
+            NEIGHBOURS type = NEIGHBOURS.NEIGHBOUR_MOORE;
+            int NEIGHBOUR_ME = 4; 
+
+            int NEIGHBOUR_MAX = type == NEIGHBOURS.NEIGHBOUR_MOORE ? 9 : 5;
+
+            for (int i = 0; i < rounds; i++)
+            {
+                water += rain;
+
+                sediment = terrain * water;
+                terrain -= sediment;
+
+                for (int x = 1; x < w - 1; x++)
+                {
+                    for (int y = 1; y < h - 1; y++)
+                    {
+                        double[] heights = new double[NEIGHBOUR_MAX];
+                        double[] diffs = new double[NEIGHBOUR_MAX];
+
+                        double heightCenter = map[x, y];
+
+                        for (int j = 0; j < NEIGHBOUR_MAX; j++)
+                        {
+                            if (j != NEIGHBOUR_ME)
+                            {
+                                int[] coords = neighbours(type, j);
+                                coords[0] += x;
+                                coords[1] += y;
+
+                                heights[j] = map[coords[0], coords[1]] + water.map[coords[0], coords[1]] + sediment.map[coords[0], coords[1]];
+                                diffs[j] = heightCenter - heights[j];
+                            }
+                        }
+
+                        double totalHeight = 0;
+                        double totalHeightDiff = 0;
+                        int totalCellsCounted = 1;
+
+                        for (int j = 0; j < NEIGHBOUR_MAX; j++)
+                        {
+                            if (j != NEIGHBOUR_ME)
+                            {
+                                if (diffs[j] > 0)
+                                {
+                                    totalHeight += heights[j];
+                                    totalHeightDiff += diffs[j];
+                                    totalCellsCounted++;
+                                }
+                            }
+                        }
+
+                        if (totalCellsCounted == 1)
+                            continue;
+
+                        double averageHeight = totalHeight / totalCellsCounted;
+                        double waterAmount = Math.Min(water.map[x, y], heightCenter - averageHeight);
+
+                        // TODO: Check this.
+                        waterFlow.map[x, y] += waterFlow.map[x, y] - waterAmount;
+
+                        double totalInverseDiff = waterAmount / totalHeightDiff;
+
+                        for (int j = 0; j < NEIGHBOUR_MAX; j++)
+                        {
+                            if (j != NEIGHBOUR_ME)
+                            {
+                                int[] coords = neighbours(type, j);
+                                coords[0] += x;
+                                coords[1] += y;
+
+                                if (diffs[j] > 0)
+                                {
+                                    waterFlow.setWrap(coords[0], coords[1], waterFlow.map[coords[0], coords[1]] + diffs[j] * totalInverseDiff);
+                                }
+                            }
+                        }
+                    }
+                }
+
+                water += waterFlow;
+                waterFlow.fill(0);
+
+                water *= evaporation;
+
+                for (int x = 0; x < w; x++)
+                {
+                    for (int y = 0; y < h; y++)
+                    {
+                        double deposition = sediment.map[x, y] - water.map[x, y] * solubility;
+                        if (deposition > 0)
+                        {
+                            sediment.map[x, y] -= deposition;
+                            terrain.map[x, y] += deposition;
+                        }
+                    }
+                }
+
+            }
+        }
+    }
+}
\ No newline at end of file