Gulf Lowland

Origin at a maintained structure on a subtropical eastern coast: concrete-block construction, flat roof, solar array, instrument mast. A short connector track (approximately 80 km, unpaved, coastal) links this point to the southern terminus of Eastern Seaboard. The route departs west on a former coastal highway. Road surface is degraded asphalt over sand, with sections undermined by tidal erosion. Vegetation is subtropical: live oak, palm, saw palmetto. The road follows a barrier ridge at 5–15 m elevation, with tidal marsh to the south and low forest to the north. Former settlement evidence is moderate—foundations, road junctions, a collapsed water tower at km 140. At km 200, the terrain shifts inland from the coast. The road turns northwest and enters a zone of low rolling hills (maximum elevation 80 m) with mixed hardwood forest. Road surface improves on the higher ground.

Surface

55% degraded asphalt, 20% sand, 15% gravel, 10% soil

Max. gradient

6%

Obstacles

1 >300 mm (road undercut by tidal erosion)

Bayou and hardwood bottomland. The route descends from the low hills into a broad floodplain. Terrain is flat. Vegetation is dense: cypress, tupelo, water oak, understory of palmetto and vine. The canopy closes overhead in many stretches. Visibility beyond the road edge is limited. Navigation by compass bearing is essential in this segment—the road surface is intermittently visible but the dense vegetation obscures distant landmarks. The road surface alternates between degraded asphalt and compacted soil. Soil surfaces are soft when wet; differential lock should be engaged proactively in this segment. Standing water adjacent to the road is common. Three bayou crossings, the deepest at km 380: 600 mm at seasonal median, mud and silt bottom. Traction at the mud crossings is poor. Momentum is required. Do not stop in the crossing. The crossing at km 440 is shallower (300 mm) with a firmer substrate—sand over clay.

Surface

40% degraded asphalt, 10% gravel, 50% soil/mud

Max. gradient

3%

Max. ford

600 mm (+300 mm spring)

Obstacles

2 >300 mm / 1 >500 mm (bayou crossings with soft bottom)

Major river delta crossing. At km 600, the route crosses a large river delta on a bridge: steel and concrete construction, approximately 1,200 m total span over the main channel and flood plain. The bridge is structurally intact. Concrete piers show weathering but no structural compromise. The steel superstructure has surface corrosion. The deck surface is degraded—concrete with exposed rebar in some sections, potholes. Speed should not exceed 20 km/h on the bridge deck. Load capacity is estimated at 8,000 kg based on visual assessment of structural members. The river below is wide and slow-moving, carrying significant sediment. On either side of the bridge, the road crosses the flood plain on earthen embankments. The embankments are partially eroded in several places; the passable width is single-vehicle. The road surface on the embankments is compacted soil over degraded asphalt. The flood plain is inundated in spring; the embankments remain above water level except in the most extreme conditions.

Surface

60% degraded asphalt/concrete, 20% compacted soil, 20% gravel

Max. gradient

5% (embankment approach)

Max. ford

200 mm (embankment erosion points)

Obstacles

2 >300 mm / 1 >500 mm (bridge deck damage, embankment erosion)

Western delta and coastal prairie. Beyond the river delta, the terrain opens to a broad coastal prairie. Vegetation thins to grass, scattered live oak, and salt-tolerant scrub. Road surface is degraded asphalt, better preserved than the eastern segments due to the drier conditions west of the delta. Elevation is 10–30 m. The terrain is flat and open; navigation is straightforward. A faint salt smell from the south indicates proximity to the coast, though the water is not visible from the road. At km 780, an abandoned oil infrastructure complex is visible: steel derrick structures (four, standing but heavily corroded), concrete pad, pipeline right-of-way visible as a cleared linear feature heading south. None of the infrastructure is operational. The road continues west toward km 820.

Surface

65% degraded asphalt, 15% gravel, 20% soil

Max. gradient

3%

Obstacles

0 >300 mm

Route impassable. Between km 820 and km 870, the route cannot be continued. The road surface and terrain are physically unchanged—degraded asphalt, flat coastal prairie, no visible damage, no geological obstacle, no water crossing. The obstruction is not visible and not measurable by available instruments. Compass and navigation systems function normally. The route is simply not passable. Vehicles that approach the boundary from either direction are unable to proceed. The boundary has been observed at consistent positions across multiple traversals: km 820.4 from the east, km 869.7 from the west. The boundary positions do not vary with season, weather, or time of day.

The inland detour departs the main route at km 810, heading north on a former two-lane road through low hills and mixed hardwood. The detour route is 90 km, reconnecting with the main route at km 880. Road surface on the detour is degraded asphalt, condition fair. Maximum elevation on the detour: 120 m. No fords. No significant obstacles.

Post-detour reconnection. The route resumes on the coastal prairie, continuing west. Terrain and conditions are similar to the pre-obstruction segment: flat, open, degraded asphalt road surface. At km 950, the route passes through a zone of tidal estuaries. Three crossings, all tidal: depths range from 200 mm at low tide to 500 mm at high tide. Substrate is sand and gravel; traction is adequate. Tide tables should be consulted. A barrier island is accessible at km 1,050 via a former causeway—the causeway is intact but partially submerged at high tide. The island is low and sandy, approximately 8 km long, with dune grass and scattered mangrove. The causeway provides the only vehicle access. Beyond km 1,100, the terrain rises slightly (30–60 m) as the route moves inland from the coast. Vegetation shifts from salt marsh to dry grassland and mesquite.

Surface

50% degraded asphalt, 20% gravel, 20% sand, 10% soil

Max. gradient

4%

Max. ford

500 mm (tidal)

Obstacles

1 >300 mm / 1 >500 mm (causeway submersion)

Western approach and terminus. Semi-arid terrain. Mesquite, creosote, dry grassland. Elevation rises gradually to 80–120 m. Road surface is degraded asphalt in better condition than the eastern half of the route—less moisture damage. The road follows a former highway alignment through sparsely settled terrain; former habitation evidence is minimal. At km 1,380, a dry arroyo crossing: 300 mm deep, sandy bottom, steep banks on both sides. Breakover angle of 18° required. The final approach to the terminus descends to the coast through low rocky hills. The terminus is a coastal facility at a small protected bay: concrete construction, approximately 25 m × 15 m, two stories, a dish antenna approximately 4 m in diameter on the roof, a secondary antenna array, solar panels, and visible cabling. Equipment is active—rotation observed on the dish antenna, indicator lights, audible operation. A concrete pier extends into the bay. Vehicle staging on a compacted gravel area adjacent to the facility.

Surface

55% degraded asphalt, 20% gravel, 25% soil/sand

Max. gradient

8%

Obstacles

0 >300 mm