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Advanced Squad Leader Rulebook Updated and Erraticized

Navigation: Chapter B. Terrain

B21 Water Obstacles

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21.1 A Water Obstacle is a body of water large enough to stop the normal movement of men and vehicles, which cannot enter without special assistance. Any non-stream hex whose center dot is emplaced in a blue background is a Water Obstacle hex. There are four types of Water Obstacles—all of which have very similar characteristics.

21.11 CANAL: A canal is a man-made waterway one hex in width used for commercial transport between larger natural waterways and flows into a river or off the board end edge. 23H2 is an example of a canal hex.

21.12 RIVER: A river is a larger waterway usually of multi-hex width, which extends in a continuous flow of water hexes off the board end. 7E2 is an example of a river hex.

21.121 CURRENT: At the outset of any river scenario, the Current direction and force should be defined, in DYO scenarios where these factors are not known they are resolved with a dr. Place the Current counter in any applicable direction. If the dr is odd, reverse it; if even, leave it as is. This same dr, modified by the current EC (25.5), determines the Current force as per the following table



≤ 1




≥ 6


Place the Current counter in a river hex proper side up as a constant reminder of prevailing Current conditions. Current does not affect bridges or any river hex bordered on opposite sides by non-island ground (marsh inclusive) hexes (EX: 7CC4, 7K2, 7H1). Current affects fording Infantry only in that it defines "downstream". Both moderate and heavy currents affect boats and amphibious vehicles, except during the Player Turn in which they are launched or landed; slow current has no effect. Boats and amphibious units IN a river hex with moderate current must drift one hex downstream during their APh; in a heavy current they drift one hex during each APh. If there is more than one adjacent downstream hex to drift to, power boats and non-Immobile amphibious vehicles may choose the drift hex if manned by non-broken/shocked/stunned PRC. The drift hex of all paddled or abandoned boats, and abandoned or shocked/stunned/immobilized amphibians, is determined by dr: 1-3 lower hex coordinate, 4-6 higher hex coordinate. A unit does not drift into/out of marsh.

21.122 DEPTH: At the outset of any river scenario the depth should be defined as fordable, deep, or flooded. If fordable, Infantry units may attempt to ford without use of boats. Wrecks appear IN water hexes only in fordable rivers. If undefined by SSR, a river is considered to be deep. In DYO scenarios where this information is not known it can be resolved with a dr. ≤ 1 = flooded, 2-5 = deep, ≥ 6 = fordable. This dr is modified by the current EC drm (25.5). A flooded river transforms adjacent marsh to river terrain (16.6); a fordable river transforms such marsh to mudflats (16.7).


21.13 POND: A pond for game purposes is essentially a land-locked river, lacking the natural flow patterns of a river because it is surrounded by land on all sides. 7CC9 and 17N7 are examples of a pond hex. No dr is made to determine the depth of a pond; 21.2 applies instead. A pond can exist without containing a hex center dot (such as the one in 24L9-M9), but in this case the hex is not considered a Water Obstacle hex (although the pond hexside is a Water Obstacle) and can be entered across any non-all-water hexside. An amphibious vehicle attempting to cross any all-water hexside into a non-Water Obstacle hex [EXC: marsh; 16.42] must expend one amphibious mode MP plus the normal non-amphibious MP cost of that hex. Wrecks appear in a pond only if it is defined by SSR as fordable.

21.14 LAKE/OCEAN: A lake/ocean is a body of water so large that it extends unimpeded across the entire length of a mapboard and covers that mapboard edge with Water Obstacle hexes.

21.2 All Water Obstacles are one level beneath the surrounding terrain (usually level -1), so a Crest Line is formed where a Water Obstacle hex meets a ground level or higher terrain feature [EXC: 21.21]. Therefore a unit IN a Water Obstacle hex may trace a LOS into only the initial hex of each level above it; however, this LOS can be blocked by other LOS requirements (such as distance from a Crest Line; 10.23). Similarly, a unit on a higher level may trace a LOS INTO a Water Obstacle hex only if between it and the Water Obstacle hex, there are no other intervening hexsides (other than its own) of equal or higher elevation to it.

21.21 If a river is defined as flooded it is one level higher than normal (i.e., usually level 0). All ponds in a scenario that has a flooded river are also one level higher than normal. Such increases in the level of a Water Obstacle (or stream; 20.44) do not prohibit normal movement under a bridge (21.4) in that water hex.

EX: 7AA10 would have to be at level 1 or higher to give it a view INTO the river through AA9. However, if the river were defined as flooded, both AA8 and BB9 would be at ground level (and BB8 would be considered a river hex; 16.6).

21.3 Provided a LOS to it exists, a Water Obstacle is considered Open Ground for TEM and Rout purposes (see bridges; 6.32).

21.4 Entrance of a Water Obstacle hex is usually limited to units on a bridge, boat, or amphibious vehicle. Otherwise, entrance is limited to swimming or fording by Personnel units. The rules for swimming and boats are highly specialized and therefore described separately in Chapter E.

21.41 FORDING: Fording may be attempted by Infantry/Cavalry only in river hexes defined as both fordable and non-frigid. Pushing motorcycles/Guns is not allowed while fording. Entrance of such a hex costs the unit's entire MF allotment and is considered Hazardous Movement for as long as the unit is in that hex. There is no penalty for leaving a Water Obstacle hex other than the doubling of MF for each higher elevation entered [EXC: Abrupt Elevation Change; 10.5]. Fording units may not move upstream directly against a heavy current. Fording units are immune to Pin effects. A Water Obstacle cannot be entered (via fording) during the APh, but can be left in the APh. Mortars, MMG, and HMG must be dm to be portaged by fording Infantry/Cavalry.

EX: Movement from 8CC8 across the Double Crest Line to the wooded, level 1 hex BB8 requires six MF (2 [to ascend the intermediate level; 10.51] + 4 [to enter a higher wooded hex; A4.133] = 6).

       A4.62, A23.7, B8.3, B21.41, B23.41, B24.7 & C10.3


21.42  Fording units may fire only their inherent FP and only as Area Fire (which would be halved again for AFPh fire).

21.43 Fording units which break may not use Low Crawl and are therefore very vulnerable to Interdiction. Broken units in a Water Obstacle must rout; they may not remain in their current Location even if Disrupted.

21.5 No Fortifications are allowed in a Water Obstacle.

21.6 ICE: All Water Obstacles (except an ocean) freeze in sub-zero temperature scenarios. When frozen, Water Obstacle hexes are treated as Open Ground for all purposes. Ice is removed from any hex in which an Original HE attack DR scores a KIA on the IFT or when the ice collapses. Mark such hexes as clear water by the placement of a coin or a Collapsed Ice counter (available in ARMIES OF OBLIVION). The ice may collapse under the weight of any vehicle of ≥ five tons as per the rules for bridge collapse (6.42; treating the Weight Limit for all ice hexes as equal to that of the highest weight sustained thus far by any ice hex), causing the elimination of all units in that hex and all future vehicles ≥ that weight venturing onto the ice. Wire and unhidden mines are the only Fortifications allowed in an ice hex.

       B20.7, B21.6, E3.722, & G13.42

       B6.42 & B21.6

       B6.42 & B21.6