diff --git a/plan/scenarios.md b/plan/scenarios.md
index c79ea63..08c41bd 100644
--- a/plan/scenarios.md
+++ b/plan/scenarios.md
@@ -30,6 +30,8 @@ Forces come from helm, which already indexes year, BV, role and tonnage.
       assumption about north and south. Three of the suite's 24 scenarios fail,
       all on `Map Set 4/16x17 River Delta 1`; the other 21 pass.
       `--allow-uncrossable` demotes it to a warning
+- [x] **Drop `River Delta 1` from the map pool** and regenerate the suite, so
+      the check has nothing left to reject. Epoch 3
 - [ ] Asymmetric scenarios, once the mirrored baseline is stable
 - [ ] Objective scenarios, which [goals](goals.md) needs
 
@@ -43,6 +45,8 @@ why the connectivity check treats any water as closed: depth 1 is the line that
 separates `River Delta 1`, which never produced a fight, from `Large Lakes 1`,
 which is wetter and plays fine. At depth 2 the check flags nothing.
 
-The three `River Delta 1` scenarios are still in the suite. Regenerating them
-out changes the suite fingerprint and makes every recorded baseline
-incomparable, so it is its own change.
+`River Delta 1` is now out of `MAPS` and the suite is regenerated without it;
+`sds validate --suite scenarios/suite` passes all 24. That changes the suite
+fingerprint and makes every earlier baseline incomparable, which is what
+epoch 3 records. It is the only board of the twelve that fails, so no other
+exclusion was needed.
diff --git a/scenarios/suite/1v1-clan-invasion-s101011.mms b/scenarios/suite/1v1-clan-invasion-s101011.mms
index 862fe24..209a52e 100644
--- a/scenarios/suite/1v1-clan-invasion-s101011.mms
+++ b/scenarios/suite/1v1-clan-invasion-s101011.mms
@@ -12,7 +12,7 @@ Name=1v1-clan-invasion-s101011
 Description=Mirrored 1v1, clan-invasion era, 1838 BV a side, seed 101011.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 4/16x17 River Delta 1
+Maps=Map Set 5/16x17 Deep Canyon 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/1v1-jihad-s102011.mms b/scenarios/suite/1v1-jihad-s102011.mms
index 5fab681..14b07ba 100644
--- a/scenarios/suite/1v1-jihad-s102011.mms
+++ b/scenarios/suite/1v1-jihad-s102011.mms
@@ -12,7 +12,7 @@ Name=1v1-jihad-s102011
 Description=Mirrored 1v1, jihad era, 1325 BV a side, seed 102011.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 5/16x17 Open Terrain 1
+Maps=Map Set 2/16x17 Mountain Lake
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/1v1-succession-wars-s100010.mms b/scenarios/suite/1v1-succession-wars-s100010.mms
index e20e581..507a3ab 100644
--- a/scenarios/suite/1v1-succession-wars-s100010.mms
+++ b/scenarios/suite/1v1-succession-wars-s100010.mms
@@ -12,7 +12,7 @@ Name=1v1-succession-wars-s100010
 Description=Mirrored 1v1, succession-wars era, 1319 BV a side, seed 100010.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 4/16x17 River Delta 1
+Maps=Map Set 5/16x17 Deep Canyon 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/1v1-succession-wars-s100011.mms b/scenarios/suite/1v1-succession-wars-s100011.mms
index fc1fe92..127cb4f 100644
--- a/scenarios/suite/1v1-succession-wars-s100011.mms
+++ b/scenarios/suite/1v1-succession-wars-s100011.mms
@@ -12,7 +12,7 @@ Name=1v1-succession-wars-s100011
 Description=Mirrored 1v1, succession-wars era, 1242 BV a side, seed 100011.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 5/16x17 Open Terrain 1
+Maps=Map Set 5/16x17 Deep Canyon 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/2v2-clan-invasion-s101020.mms b/scenarios/suite/2v2-clan-invasion-s101020.mms
index a9e8015..6b3cb35 100644
--- a/scenarios/suite/2v2-clan-invasion-s101020.mms
+++ b/scenarios/suite/2v2-clan-invasion-s101020.mms
@@ -12,7 +12,7 @@ Name=2v2-clan-invasion-s101020
 Description=Mirrored 2v2, clan-invasion era, 2847 BV a side, seed 101020.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 4/16x17 River Delta 1
+Maps=Map Set 5/16x17 Deep Canyon 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/2v2-clan-invasion-s101021.mms b/scenarios/suite/2v2-clan-invasion-s101021.mms
index 6229816..838f4c6 100644
--- a/scenarios/suite/2v2-clan-invasion-s101021.mms
+++ b/scenarios/suite/2v2-clan-invasion-s101021.mms
@@ -12,7 +12,7 @@ Name=2v2-clan-invasion-s101021
 Description=Mirrored 2v2, clan-invasion era, 2736 BV a side, seed 101021.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 5/16x17 Deep Canyon 1
+Maps=Map Set 5/16x17 Large Mountain 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/2v2-jihad-s102021.mms b/scenarios/suite/2v2-jihad-s102021.mms
index 00c2f83..fff4449 100644
--- a/scenarios/suite/2v2-jihad-s102021.mms
+++ b/scenarios/suite/2v2-jihad-s102021.mms
@@ -12,7 +12,7 @@ Name=2v2-jihad-s102021
 Description=Mirrored 2v2, jihad era, 2694 BV a side, seed 102021.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 5/16x17 Open Terrain 1
+Maps=Map Set 5/16x17 Deep Canyon 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/4v4-clan-invasion-s101040.mms b/scenarios/suite/4v4-clan-invasion-s101040.mms
index 4b1388f..da8989e 100644
--- a/scenarios/suite/4v4-clan-invasion-s101040.mms
+++ b/scenarios/suite/4v4-clan-invasion-s101040.mms
@@ -12,7 +12,7 @@ Name=4v4-clan-invasion-s101040
 Description=Mirrored 4v4, clan-invasion era, 4898 BV a side, seed 101040.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 5/16x17 Large Mountain 1
+Maps=Map Set 5/16x17 Open Terrain 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/4v4-succession-wars-s100040.mms b/scenarios/suite/4v4-succession-wars-s100040.mms
index 5a3243e..90f5bc4 100644
--- a/scenarios/suite/4v4-succession-wars-s100040.mms
+++ b/scenarios/suite/4v4-succession-wars-s100040.mms
@@ -12,7 +12,7 @@ Name=4v4-succession-wars-s100040
 Description=Mirrored 4v4, succession-wars era, 4427 BV a side, seed 100040.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 5/16x17 Large Mountain 1
+Maps=Map Set 5/16x17 Open Terrain 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/4v4-succession-wars-s100041.mms b/scenarios/suite/4v4-succession-wars-s100041.mms
index 754d9f4..ca729bd 100644
--- a/scenarios/suite/4v4-succession-wars-s100041.mms
+++ b/scenarios/suite/4v4-succession-wars-s100041.mms
@@ -12,7 +12,7 @@ Name=4v4-succession-wars-s100041
 Description=Mirrored 4v4, succession-wars era, 4545 BV a side, seed 100041.
 BoardWidth=1
 BoardHeight=1
-Maps=Map Set 5/16x17 Deep Canyon 1
+Maps=Map Set 5/16x17 Large Mountain 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/8v8-clan-invasion-s101080.mms b/scenarios/suite/8v8-clan-invasion-s101080.mms
index c789211..b812c48 100644
--- a/scenarios/suite/8v8-clan-invasion-s101080.mms
+++ b/scenarios/suite/8v8-clan-invasion-s101080.mms
@@ -12,7 +12,7 @@ Name=8v8-clan-invasion-s101080
 Description=Mirrored 8v8, clan-invasion era, 15006 BV a side, seed 101080.
 BoardWidth=2
 BoardHeight=1
-Maps=Map Set 5/16x17 Open Terrain 1,Map Set 2/16x17 BattleTech
+Maps=Map Set 2/16x17 BattleTech,Map Set 5/16x17 Open Terrain 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/8v8-jihad-s102080.mms b/scenarios/suite/8v8-jihad-s102080.mms
index d2b5a6c..906e748 100644
--- a/scenarios/suite/8v8-jihad-s102080.mms
+++ b/scenarios/suite/8v8-jihad-s102080.mms
@@ -12,7 +12,7 @@ Name=8v8-jihad-s102080
 Description=Mirrored 8v8, jihad era, 14834 BV a side, seed 102080.
 BoardWidth=2
 BoardHeight=1
-Maps=Map Set 2/16x17 Lake Area,Map Set 5/16x17 Deep Canyon 1
+Maps=Map Set 2/16x17 Lake Area,Map Set 5/16x17 Large Mountain 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/scenarios/suite/8v8-succession-wars-s100081.mms b/scenarios/suite/8v8-succession-wars-s100081.mms
index d018f98..153397f 100644
--- a/scenarios/suite/8v8-succession-wars-s100081.mms
+++ b/scenarios/suite/8v8-succession-wars-s100081.mms
@@ -12,7 +12,7 @@ Name=8v8-succession-wars-s100081
 Description=Mirrored 8v8, succession-wars era, 7809 BV a side, seed 100081.
 BoardWidth=2
 BoardHeight=1
-Maps=Map Set 2/16x17 Lake Area,Map Set 5/16x17 Deep Canyon 1
+Maps=Map Set 2/16x17 Lake Area,Map Set 5/16x17 Large Mountain 1
 Factions=North,South
 Location_North=N
 Location_South=S
diff --git a/sds/epoch.py b/sds/epoch.py
index fdf0907..dcd1058 100644
--- a/sds/epoch.py
+++ b/sds/epoch.py
@@ -19,7 +19,7 @@ Add a line to `CHANGES` when you bump it. A number with no note is worse than
 no number.
 """
 
-EPOCH = 2
+EPOCH = 3
 
 CHANGES = {
     1: "First measured harness: BV-destroyed victory at 70%, 40-round limit.",
@@ -28,6 +28,12 @@ CHANGES = {
         "destroyed Mek left a 0-BV MekWarrior on the board, so a wiped-out side "
         "was still a live enemy and the game ran to the round limit."
     ),
+    3: (
+        "`Map Set 4/16x17 River Delta 1` is out of the suite's map pool. No "
+        "water-free path joins its deployment edges, so a match on it could "
+        "only ever reach the round limit at 100% BV a side. `sds validate` "
+        "rejects such a board."
+    ),
 }
 
 
diff --git a/sds/scenario.py b/sds/scenario.py
index 7913eb8..6150293 100644
--- a/sds/scenario.py
+++ b/sds/scenario.py
@@ -49,7 +49,13 @@ MAPS = [
     "Map Set 3/16x17 Desert Mountain 1",
     "Map Set 4/16x17 Heavy Forest 1",
     "Map Set 4/16x17 Large Lakes 1",
-    "Map Set 4/16x17 River Delta 1",
+    # "Map Set 4/16x17 River Delta 1" is deliberately absent. No water-free
+    # path joins its two deployment edges: 119 of its 272 hexes are water and
+    # they band across the middle. Two Princesses never make contact and the
+    # game runs to the round limit at 100% BV a side. Of the twelve boards this
+    # list started with it is the only one that fails - water fraction is not
+    # the test, connectivity is, and `Large Lakes 1` is 50% water and plays
+    # fine. `sds validate` now checks this; see scenarios.md.
     "Map Set 5/16x17 Deep Canyon 1",
     "Map Set 5/16x17 Large Mountain 1",
     "Map Set 5/16x17 Open Terrain 1",
diff --git a/tests/test_crossing.py b/tests/test_crossing.py
index 2229cb4..7895eea 100644
--- a/tests/test_crossing.py
+++ b/tests/test_crossing.py
@@ -128,9 +128,15 @@ class TestSuiteMaps(unittest.TestCase):
         bottom = {(x, y) for x in range(width) for y in range(height - self.ZONE, height)}
         return connects(dry, top, bottom)
 
-    def test_river_delta_is_the_only_uncrossable_map(self):
+    def test_every_map_in_the_pool_is_crossable(self):
         blocked = sorted(name for name in MAPS if not self.crossable(name))
-        self.assertEqual(blocked, ["Map Set 4/16x17 River Delta 1"])
+        self.assertEqual(blocked, [])
+
+    def test_river_delta_is_why_the_pool_excludes_it(self):
+        # Named rather than drawn from MAPS: it was removed from the pool, and
+        # the reason it was removed is the thing worth keeping a test on.
+        self.assertFalse(self.crossable("Map Set 4/16x17 River Delta 1"))
+        self.assertNotIn("Map Set 4/16x17 River Delta 1", MAPS)
 
 
 if __name__ == "__main__":