Regional Terrain Survey

Temperate rainforest biome transitioning to dry chaparral in the southern third. Terrain follows a former multi-lane coastal highway, now substantially degraded. Sea cliffs present along the central segment; highest cliffs reach 380 m above datum. River valleys cut perpendicular to the coast at regular intervals. Elevation range: 0 to 520 m. Topographic relief is pronounced in the northern and central segments (60+ m per 10 km), with sustained grades exceeding 10%. The southern segment flattens to a broad coastal terrace.

Surface composition is heterogeneous. Degraded asphalt comprises 35–45% of the route surface, primarily on the former main roadway. Gravel and compacted stone comprise 30–40%, with highest concentration in areas of asphalt collapse and on constructed fire tracks. Exposed soil, sand, and washed-out sections comprise 20–30%. Canopy encroachment narrows single-vehicle width passable tracks to 3–4 m in the northern conifer stretch; this does not reduce bearing capacity, only visibility and turning radius.

Drainage is toward the western ocean via short, steep river systems. Three tidal fords are documented. Ford depths vary with tidal cycle; median low-tide depths are 220–380 mm. High-tide depths exceed 1,100 mm. Spring snowmelt increases upper-watershed ford depths by 60–80 mm for 3–5 weeks. No permanent standing water is common on the road surface owing to grade and drainage, except in the southern flatlands where clay-silt substrate may pond after precipitation. Fog is frequent year-round along headlands; visibility below 100 m occurs for sustained periods in autumn and winter.

Observable structures include a maintained dock facility on the northern inlet (timber and steel construction, solar array, gravel staging area); a fenced perimeter facility of approximately forty acres in the central segment (chain-link fence, intact gate, multiple structures of unconfirmed function); and a concrete pier with block storage structures at the southern terminus (40 m extension, intact cleats, serviceable condition).

High desert and semi-arid terrain dominated by alluvial basins, alkaline flats, and mesa-and-canyon topography. Elevation range: 1,200 to 2,300 m. Sustained grades are moderate (6–9% typical) with localized steeper segments where tracks negotiate canyon walls or basin margins. The terrain is characterized by lateral space and minimal vegetation, offering multiple track options across most of the region. Actual bearing surfaces (where passage is mandatory or optimal) are constrained by canyon bottoms, drainage channels, and basin margins.

Surface composition is predominantly soil and exposed rock. Compacted dirt and mixed sediment comprise 50–65% of traversable surfaces. Gravel and alluvial fans comprise 20–30%. Exposed bedrock, usually red sandstone or similar, comprises 10–20%. Asphalt is negligible; remnants occur in isolated locations but not as continuous routes. Clay-silt substrates occur in basin lows and are prone to saturation after precipitation; bearing capacity in these zones drops to 40–60 kPa when wet. Dust mobility is high; wind-blown surface redistribution occurs seasonally.

Drainage is through canyon systems toward internal basins. No through-drainage to the ocean occurs in this region. Seasonally dry stream channels (arroyos) are common; after summer thunderstorms, flash-flow conditions develop rapidly and persist for 1–3 hours. Ford depths can increase from 0 to 800+ mm within 30 minutes during peak runoff. Alkaline flat substrates retain standing water, forming temporary salt lakes with unknown bearing capacity. When dry, alkaline flats are firm but corrosive to unprotected metal surfaces.

Observable structures include multiple corroded vehicle frames (age indeterminate) scattered across open bajadas; a concrete dam structure in a side canyon (spillway functional, reservoir empty); and several clusters of partially collapsed wooden or concrete foundations (age and function unclear).

High mountain terrain along the continental watershed. Elevation range: 1,400 to 3,400 m, with the steepest grades and most variable conditions of all regions. Topography is characterized by glacial valleys, talus fields, scree slopes, and alpine meadows. Grade variation is extreme: sustained descents of 12–15% are common, with isolated segments exceeding 20%. Ascents of 10–14% are typical over 500–1,000 m climbs. Terrain above 2,800 m exhibits permanent and semi-permanent snowfields, permafrost in shaded zones, and active freeze-thaw cycling.

Surface composition is dominated by unconsolidated materials: loose scree comprises 40–55% of high-elevation terrain (above 2,500 m). Compacted stone and gravel comprise 20–35%. Alpine meadow (vegetated soil with firm bearing when dry) comprises 10–20% of the lower alpine segment (1,400–2,000 m). Exposed bedrock comprises 5–15%. No asphalt exists in this region. Scree is mobile and subject to freeze-thaw destabilization; surface changes year-to-year and seasonally within a single traverse window.

Drainage is the source region for all continental water systems. Streams in this zone are swift, cold, and prone to rapid rise with snowmelt or precipitation. Fords in the alpine region exceed 1,000 mm from mid-April through mid-June at elevations above 2,500 m. Maximum ford depths occur in late May or early June, corresponding to peak snowmelt. Below 2,000 m, fords are passable by mid-summer. Streams above 2,800 m may be bridged by snow and ice for the majority of the calendar year; melt timing is unpredictable and advance scouting is required.

Extreme seasonal variation is the dominant characteristic. Winter (late autumn through mid-spring) brings snow accumulation at 100–200 mm per metre of vertical. Freeze-thaw cycling destabilizes scree and causes heave in clay and silt substrates. Passes above 2,800 m are effectively impassable (snowpack depth 2–4+ m). Spring (late April through early June) is the most demanding season: rapid snowmelt, scree instability, flash flooding in canyon systems, and unpredictable weather. Summer (mid-June through early September) offers the most favorable passage conditions with stable surfaces and manageable ford depths. Autumn (early September through late October) presents cooling trends and early snow at highest elevations; passes above 3,200 m may be snow-blocked by mid-October.

Observable structures are sparse. Weathered wooden trestle remnants are visible in two side-canyon locations (date of origin unknown). A concrete trigonometric station (intact) is present at approximately 3,100 m elevation. No maintained facilities are evident.

Continental grassland and semi-arid transition zone spanning the interior basins. Elevation range: 180 to 1,600 m, with the flattest topography of any region. Grades rarely exceed 4%. The landscape is characterized by broad alluvial valleys, scattered buttes, and extensive grassland with minimal tree cover (except along riparian corridors). Visible horizon distance often exceeds 20 km. Vegetation density varies from sparse (western region) to dense (eastern region), affecting visibility and track definition.

Surface composition is predominantly soil. Compacted earth and mixed sediment comprise 60–75% of traversable surfaces. Gravel comprises 15–25%, concentrated along ancient river channels and basin margins. Exposed bedrock is rare (2–5%). Asphalt remnants occur in isolated linear segments (former highways) but do not constitute a reliable route surface. Heavy clay substrates occur in the eastern lowlands and in specific fluvial zones; these lose bearing capacity rapidly in wet conditions (down to 40–60 kPa when saturated). Silty soils in the central and eastern portions are prone to erosion and gully formation after heavy precipitation.

Drainage is primarily through meandering river systems. Major rivers in the eastern portion are perennial and may exceed 2,000 m wide in some locations; current speed is typically 1–2 m/s. Seasonal tributary streams (called "creeks" in the western portion) may flow year-round or only during spring runoff, depending on groundwater levels. Fords are frequent and generally shallow (median 300–500 mm) except during spring snowmelt, when depths increase to 600–1,000+ mm. Seasonal standing water is common in clay-rich zones and persists for weeks after precipitation.

The western interior lowland (semi-arid region) is characterized by sparse vegetation, high wind exposure, and minimal shade. Vegetation-free "blown-bare" patches create isolated sand and silt dunes; these are unstable and reduce traction. Summer temperatures are extreme (40–50 °C reported). The eastern interior lowland (humid region) supports dense native grassland, with higher vegetation density affecting visibility and track definition. This region receives higher precipitation (40–120 mm/month year-round) and maintains more reliable track definition due to more frequent transit and water-binding of soil.

Observable structures are sparse and isolated. Corroded metal agricultural equipment (windmill frames, stock tanks) is scattered across the landscape at regular intervals, spaced at regular intervals. A few concrete block foundations are visible, degraded, their original function unclear. No maintained facilities are evident in the interior lowland.

Transitional zone between the eastern mountain foothills and the coastal plain. Elevation range: 0 to 480 m. Topography varies from rolling hills (piedmont proper) to flat coastal lowlands. Grades are generally moderate (5–8% in the piedmont, less than 3% on the coastal plain). The region is extensively vegetated with deciduous forest in the piedmont and mixed hardwood-pine forest transitioning to marsh and tidal estuary in the coastal zone. Canopy is dense, reducing visibility and solar penetration to the road surface.

Surface composition is dominantly soil. The piedmont is characterized by red clay and silt (laterite soils) with 55–70% fine substrates, 20–30% gravel and stone, and 5–15% exposed bedrock (granite, metamorphic schist). The coastal plain is characterized by gray and black silt-clay with 65–80% fine substrates, 15–20% sand, and 2–5% gravel. Asphalt is present as remnants of the former highway system; these are degraded but offer better surface conditions than soil in areas where asphalt remains intact (typically 20–30% of coastal plain routes, less in piedmont). Former road bases (now exposed after asphalt loss) are compacted stone and provide moderate bearing capacity.

Drainage is toward the eastern coast via numerous river systems. Major rivers are tidal for the final 50–200 km of their length; tidal influence raises and lowers river levels by 1–2 m on a semi-diurnal cycle. Tidal fords may be passable only during a narrow window at low tide. Most river crossings in the piedmont are bridged (concrete beam or steel truss), but many bridges are deteriorated and require load assessment. Coastal plain rivers are typically wider and deeper; fords may be impassable year-round. Spring snowmelt from northern elevations increases river levels by 300–600 mm for 4–6 weeks; this eliminates some ford windows entirely during that season.

The coastal estuary and marsh zone is characterized by soft substrates (peat, organic silt), standing water, and complex tidal hydrology. Tidal marshes flood and drain twice per day; elevation variation is 0.5–2+ m depending on the estuary. Vehicle passage through marsh is possible only on established tracks that are elevated or compacted; soft-bottomed areas offer insufficient bearing capacity. Salt marsh vegetation (spartina grass, rushes) is dense and restricts visibility. Tidal range (difference between high and low tide) is 1–2 m on the open coast, increasing to 2–3 m in some estuaries.

Observable structures are numerous. Wooden and brick buildings in various states of degradation are scattered throughout the region, many partially reclaimed by vegetation. A few concrete structures (bridges, dams, storm surge walls) remain intact. No maintained facilities are evident.

Floodplain and coastal lowland region in the subtropical zone. Elevation range: 0 to 50 m. Topography is extremely flat; visible grade change over 10 km distances is typically less than 50 mm. The region is characterized by broad floodplains, meandering rivers, coastal swamps, and tidal estuaries. Vegetation is dense (bald cypress, tupelo, marsh grasses) and often completely inundates the landscape, leaving few exposed soil or rock surfaces.

Surface composition is dominated by organic-rich substrates. Peat and organic silt comprise 60–75% of the landscape. Mineral clay comprises 15–25%. Sand is rare (2–5%, concentrated on natural levees and historic dunes). Gravel is negligible. Bearing capacity of peat and organic substrates ranges from 30–60 kPa when dry to 10–40 kPa when saturated. There is no asphalt in this region; all historic road bases have been either inundated or destroyed.

Drainage is through slow, meandering rivers and extensive swamp systems. Rivers in this zone are perennial with slow current (0.3–0.8 m/s). River width varies from 500 m to 5+ km depending on location. Seasonally, the entire floodplain becomes inundated; swamp water depth ranges from 0.5–3+ m depending on rainfall and upstream conditions. No dry season occurs in much of this region; water levels fluctuate but rarely fully recede.

Seasonal flooding is the dominant characteristic. Winter and spring (December through June) bring the highest water levels due to combination of precipitation and upstream runoff. Summer and autumn bring slight reduction in water levels but not full recession. The floodplain floods when river stage rises above the natural levees. Flooding duration varies: some low-lying areas are flooded continuously; others may drain for 2–4 months during late summer and autumn. When inundated, bearing capacity becomes effectively zero; only elevated roads, dikes, and elevated natural levees offer passage.

Observable structures are minimal. A few concrete bridge pilings are visible (original structures destroyed or submerged). Wooden structures in various states of degradation are scattered throughout, many partially submerged or rotted. Dikes and canal systems are present but unmaintained; silting and vegetation encroachment have reduced their function.

The six primary continental regions present distinct terrain, drainage, and seasonal characteristics. The following table summarizes key parameters for route planning.

Terrain difficulty is not linear with elevation. The alpine divide, despite highest elevation, offers the most challenging passage in spring and autumn due to scree instability and ford-depth variability. The subtropical lowland offers the most constrained routing due to permanent inundation. The interior lowland offers the most stable year-round conditions and the flattest, most predictable passage, but seasonal saturation of clay zones eliminates some windows. The western coast offers the most varied terrain and the most complex drainage (tidal effects), requiring tight timing of ford attempts. The intermountain basin offers the most open terrain with multiple route options but is prone to flash-flood hazards in arroyos.