Linear terrain includes such things as streams and rivers, chasms, ravines and even roads. Unlike low and high linear obstacles, which rise up from the battlefield, linear terrain features are best described as 'cutting into the battlefield, thus presenting obstacles to movement and hazards to life and limb due to either their width, their crashing waters, their hazardous footing or their (potentially limitless) depth.
"How Long Is A River?"
Every linear terrain feature is divided into sections, each measuring 12" long and up to 4" wide in the case of a 'narrow' feature, or between 4" and 8" wide in the case of a 'wide' feature. Each section is equal to one terrain feature for the purposes of determining how many terrain features should be placed on the battlefield. Each section may include a single bend of up to 90°, or a single fork or junction.
The maximum length of a linear terrain feature depends upon what it represents and the size of the battlefield:
An especially hazardous linear terrain feature, one that counts as dangerous or impassable terrain, such as a fast flowing river or deep chasm, may not be longer than half the length of the longest edge of the battlefield. For example, a battlefield that measures 48" x 72" may include an especially hazardous linear terrain feature measuring up to 36" in length.
An easily traversed linear terrain feature, one that counts as open ground or difficult terrain, such as a narrow stream or a well-maintained road, may be any length, twisting and turning across the battlefield and around other terrain as required.
Placing Linear Terrain Features
Linear terrain features are placed as described in the Warhammer: the Old World rulebook. A linear terrain feature must be placed with one end touching the edge of the battlefield. The other end must:
Touch a different edge of the battlefield.
Meet another terrain feature, where the linear terrain feature will end (for example, a stream may end where it meets a pond).
Taper to a point, where the linear terrain feature will end.
Bridges & Fords
Streams, rivers, chasms, ravines and gullies can be crossed by bridges. Rivers and streams can also be crossed by fords. You may include a single bridge or ford measuring up to 3" wide per 12" linear terrain feature. On longer linear terrain features, these can be combined together to make wider bridges and fords.
A bridge counts as open ground. A ford counts as difficult terrain.
Fast-Flowing Water
A river that touches two table edges may be 'fast-flowing, in which case you will need to randomly determine the direction it flows. Should a unit have a quarter (25%) or more of its models within a fast flowing river during its Start of Turn sub-phase, it must make a Strength test. If this test is failed, the unit slides D3" along the river in the direction it flows.
Well-Maintained Roads
Marching troops can move quickly along a well-maintained' road. A unit that begins and ends a march move with half (50%) or more of its models upon the same well-maintained road, and that does not leave that road whilst moving, may move an additional D3".