Natural Divides
Definition
Natural divides are physical features that separate drainage basins, ecosystems, or biogeographic regions—typically ridgelines, watershed boundaries, desert fronts, or major escarpments. They guide movement of water, species, and people, influencing culture and politics. In mapping, divides are derived from DEMs through flow-direction algorithms and then refined with field knowledge and geology. Divides are not always sharp; karst regions and endorheic basins complicate boundaries. Natural divides also affect infrastructure costs: tunnels, passes, and pipelines must cross them. Recognizing divides helps manage transboundary resources and hazards that follow watersheds rather than administrative lines. Interpretations benefit from cross-sections that show how wind and moisture behave on either side of major divides. Interpretations benefit from cross-sections that show how wind and moisture behave on either side of major divides. Provide clear usage notes, QA artifacts, and version history to aid reuse and review. Provide clear usage notes, QA artifacts, and version history to aid reuse and review. Provide clear usage notes, QA artifacts, and version history to aid reuse and review.
Application
Water managers allocate rights by basin; conservationists plan corridors along divides; historians interpret settlement patterns; emergency planners anticipate where spills or fires may jump divides. Tourism markets scenic ridge routes and long-distance trails along divides.
FAQ
How accurate are DEM-derived divides?
High-quality DEMs work well but can misplace divides where cliffs, karst, or human works alter flow. Validate with orthoimagery and field checks.
Can a divide move?
Yes—erosion, landslides, and captures can shift divides over geologic time; engineering works can reroute flow at human timescales.
How to communicate divide importance to the public?
Overlay governance layers to show where policies change across basins; use animations of flow to make the concept tangible.
Do divides always block species movement?
Not necessarily—some species prefer ridgelines. Analyze per species and season rather than assuming divides are barriers.