AP Syllabus focus:
‘Urban systems can be described using hierarchy, interdependence, relative size, and spacing to explain how settlements relate to one another.’
Urban hierarchy and interdependence explain how settlements of different sizes function together within a regional system, shaping connections, service distribution, and spatial organization.
Understanding Urban Hierarchy
Urban hierarchy refers to the ordered ranking of settlements—from small villages to large metropolitan areas—based on population size, economic functions, and the range of services they provide. The concept helps geographers understand how different settlements fit within a broader spatial system and how resources, people, and services flow between them.
Urban Hierarchy: A ranked system of settlements arranged by size, function, and the types of services they offer within a region.
A hierarchical arrangement allows geographers to analyze why certain cities dominate economically or politically, and how smaller towns support, and depend on, larger urban centers. This arrangement aligns with the AP specification’s emphasis on hierarchy, relative size, spacing, and interdependence as the organizing principles of urban systems.
Characteristics of Hierarchical Organization
Settlements in a hierarchy typically show predictable spatial and functional patterns:
Larger cities provide specialized, high-order services (e.g., universities, major hospitals, corporate headquarters).
Medium-sized cities offer mid-order services, such as shopping malls or regional government offices.
Small towns and villages provide low-order services, like grocery stores, gas stations, or primary schools.
Higher-ranked cities are fewer in number, while lower-ranked settlements are more numerous and evenly dispersed across space.
High-Order Services: Specialized services requiring a large population threshold and offering goods or functions people access less frequently.
These patterns influence the spacing and distribution of settlements, shaping how far people travel to access different types of goods and services.
Figure X.X Settlement hierarchy pyramid. This diagram shows how settlement size and service variety increase upward while frequency decreases. Additional labels such as “isolated dwelling” and “conurbation” extend beyond the syllabus but reinforce how different settlement types fit within a hierarchy. Source.
Relative Size and Urban Functions
The relative size of settlements matters because it reflects the scale of economic activity, transportation flows, and administrative influence. Larger settlements typically grow due to:
Greater economic diversity, supporting multiple sectors.
Larger labor markets, attracting firms and migrants.
More extensive infrastructure, enabling connectivity and expansion.
Higher accessibility, which reinforces the concentration of high-order services.
Smaller settlements, by contrast, often rely on limited industries or local services, making them more dependent on the economic health of nearby cities.
Threshold: The minimum population required to support a good or service.
Even though threshold concepts originate from central place theory, they align with hierarchical ideas by explaining why larger settlements support more complex services.
Interdependence Within Urban Systems
Urban interdependence refers to the mutual reliance between settlements of different sizes within a region. Because no settlement is fully self-sufficient, urban areas form networks of flows—people, goods, services, information, and capital—that link the hierarchy together.
How Settlements Depend on One Another
Interdependence manifests in several ways:
Economic linkages: Goods produced in small towns may be sold in regional cities; urban firms rely on labor and resources from surrounding areas.
Commuting flows: Residents of smaller towns may travel daily to larger cities for employment or specialized services.
Infrastructure networks: Transportation corridors, utilities, and communication systems connect the hierarchy, creating regional cohesion.
Service dependence: Major hospitals, airports, and government centers located in large cities serve wide hinterlands, integrating smaller settlements into broader networks.
These interactions strengthen spatial relationships and help explain why settlement patterns remain stable or shift over time.
Spacing and Distribution of Settlements
Urban hierarchy also helps explain the spacing of cities, towns, and villages across a landscape.
Figure X.X Idealized urban hierarchy and service areas. This Central Place Theory diagram illustrates how settlements form hierarchical patterns with distinct market areas and spatial relationships. Extra labels such as “range” and “threshold” extend beyond this subsubtopic but support understanding of spacing and interdependence in urban systems. Source.
Larger cities tend to be spaced farther apart because they require extensive hinterlands to support large populations and specialized services. Smaller settlements, which need fewer resources, appear more frequently and closer together.
Key spatial principles include:
Even distribution of small settlements, reflecting frequent demand for basic services.
Wider spacing for large cities, reflecting their role as regional centers.
Functional specialization, where certain cities or towns become known for specific industries, educational institutions, or services.
Network structure, where transportation routes reinforce spacing patterns by linking nodes efficiently.
Hinterland: The surrounding service area or market area influenced by a settlement.
These spatial relationships shape how residents interact with urban centers and how cities compete or collaborate for regional importance.
Urban Systems as Integrated Networks
Urban hierarchies are most meaningful when viewed as integrated urban systems, where each settlement—regardless of size—plays a role in sustaining regional development. Interdependence ensures that:
Large cities rely on smaller settlements for labor, agricultural goods, and land-intensive industries.
Small settlements rely on large cities for specialized services, higher education, cultural amenities, and employment opportunities.
Mid-sized cities bridge the gap, offering intermediate services and acting as regional hubs.
This dynamic interplay forms the backbone of national and regional settlement patterns, shaping economic geography and influencing how urbanization unfolds across space.
FAQ
Governments often allocate funding based on a settlement’s position within the hierarchy, with higher-order cities receiving larger investments for specialised infrastructure such as major hospitals, universities, and transport hubs.
Lower-order settlements may receive funding for essential services but rely on larger centres for high-cost or high-skill facilities.
This pattern reinforces the economic and functional dominance of higher-order cities while maintaining basic service provision across the settlement network.
Shifts in a settlement’s position are influenced by changes in population, economic activity, and accessibility.
Key drivers include:
New transport links increasing accessibility to wider markets
Industrial growth or decline
Policies encouraging urban development or containment
Migration trends that expand or shrink local labour markets
Upward or downward movement is usually gradual but can accelerate with major economic or infrastructural changes.
Interdependence creates predictable commuting flows between settlements of different sizes.
Residents of smaller towns often commute to larger cities for specialised employment, higher wages, and advanced services.
Larger cities depend on these commuters to fill labour gaps in sectors such as retail, healthcare, hospitality, and professional services, reinforcing daily population movements across the hierarchy.
Mid-sized settlements can occupy strategic positions within transport networks, enabling them to act as efficient connectors between smaller settlements and major cities.
They may host:
Regional government offices
Secondary hospitals
Logistics centres
Mid-order retail functions
Their location and accessibility allow them to balance local service provision with broader regional functions, giving them influence beyond what their population size alone would suggest.
Small settlements have compact hinterlands that cover short distances and provide basic services to nearby residents.
Large metropolitan areas have expansive hinterlands shaped by:
Extensive transport networks
High-order services attracting users from distant locations
Economic specialisation, drawing businesses and consumers from across a region
As cities grow, their hinterlands may overlap with those of neighbouring urban centres, creating competitive and complementary relationships in the wider urban system.
Practice Questions
Question 1 (1–3 marks)
Explain one way in which settlements of different sizes demonstrate hierarchy within an urban system.
Mark scheme:
1 mark for identifying a valid hierarchical pattern (e.g., larger settlements offering more specialised services).
1 mark for explaining how this reflects a ranking of settlements.
1 mark for linking the idea to differences in population size, functions, or service provision.
Question 2 (4–6 marks)
Using an example or examples, analyse how interdependence operates between large cities and smaller surrounding settlements within an urban hierarchy.
Mark scheme:
1 mark for defining or clearly describing interdependence.
1 mark for identifying flows between settlements (e.g., commuting, goods, services).
1 mark for explaining how large cities rely on smaller settlements (e.g., labour supply, resources, land-intensive activities).
1 mark for explaining how smaller settlements rely on large cities (e.g., specialised services, employment opportunities).
1 mark for providing a relevant example that illustrates interdependence.
1 mark for demonstrating clear analytical reasoning about how these relationships shape the functioning of an urban system.
