Core idea

A city's hinterland is not only the land that produces for it. It is the zone the city can actually serve with markets, repairs, storage, relief, tax collection, and coercive response at acceptable delay and cost. The hinterland service radius turns that relationship into a measurable field rather than a vague colored region.

This model matters because worlds often assign enormous hinterlands to major cities without showing how service quality changes with distance, terrain, or route reliability. A city that can buy grain from far away may still be unable to police, repair, or relieve that same zone effectively.

Axis	Question	Signal
Core market band	Where does exchange remain fast and routine enough to shape everyday production choices?	Day market reach, feeder cart routes, regular river trips, price integration, crop timing alignment
Repair and maintenance band	How far can tools, depots, crews, and replacements be dispatched without chronic lag?	Workshop service roads, canal maintenance loops, escortable depots, seasonal repair circuits
Relief and reserve band	Where can the city still stabilize shock before scarcity becomes local crisis?	Granary release, emergency tow, reserve wagons, flood relief reach, requisition timing
Thin frontier band	Where does service still exist on paper but become too slow, expensive, or intermittent to bind the zone tightly?	Delayed response, toll inflation, weak inspections, irregular markets, dependence on local brokers

Stress question

If one peripheral zone suffers crop loss, flood damage, or route disruption, does the city still reach it with repairs and reserves in time to matter? The answer shows the real service radius better than nominal tax or map claims.

Applied use

Nile Flood Basin State is useful because river timing and hydraulic maintenance make service reach highly seasonal but still structurally legible. Mountain Basin Civilization is the contrast case where enclosure strengthens the core but causes service reach to thin rapidly once routes leave the basin.

Transfer value

The reusable lesson is that city-region coupling should be measured through service quality, not only extraction. Once service radius is explicit, core zones, neglected peripheries, and relief politics become much easier to justify.