diff --git a/index.css b/index.css
index a1a24e92..d57a8007 100644
--- a/index.css
+++ b/index.css
@@ -991,12 +991,6 @@ body button.noicon {
   stroke-width: 0.4;
 }
 
-#controlCells > .occupied {
-  fill: #ff828240;
-  stroke: #ff8282;
-  stroke-width: 0.4;
-}
-
 #vertices > circle {
   fill: #ff0000;
   stroke: #841f1f;
diff --git a/modules/ui/rivers-editor.js b/modules/ui/rivers-editor.js
index b2b926d0..50a01ac3 100644
--- a/modules/ui/rivers-editor.js
+++ b/modules/ui/rivers-editor.js
@@ -124,18 +124,13 @@ function editRiver(id) {
     const initCell = +this.dataset.cell;
     const index = +this.dataset.i;
 
-    const occupiedCells = i.filter(i => r[i] && !river.cells.includes(i));
-    drawCells(occupiedCells, "occupied");
     let movedToCell = null;
 
     d3.event.on("drag", function () {
       const {x, y} = d3.event;
       const currentCell = findCell(x, y);
 
-      if (initCell !== currentCell) {
-        if (occupiedCells.includes(currentCell)) return;
-        movedToCell = currentCell;
-      } else movedToCell = null;
+      movedToCell = initCell !== currentCell ? currentCell : null;
 
       this.setAttribute("cx", x);
       this.setAttribute("cy", y);
@@ -149,15 +144,15 @@ function editRiver(id) {
         river.cells[index] = movedToCell;
         drawCells(river.cells, "current");
 
-        // swap river data
-        r[initCell] = 0;
-        r[movedToCell] = river.i;
-        const sourceFlux = fl[initCell];
-        fl[initCell] = fl[movedToCell];
-        fl[movedToCell] = sourceFlux;
+        if (!r[movedToCell]) {
+          // swap river data
+          r[initCell] = 0;
+          r[movedToCell] = river.i;
+          const sourceFlux = fl[initCell];
+          fl[initCell] = fl[movedToCell];
+          fl[movedToCell] = sourceFlux;
+        }
       }
-
-      debug.select("#controlCells").selectAll("polygon.available, polygon.occupied").remove();
     });
   }