Flood Susceptibility Mapping in Ankara Using M-AHP: A GIS-Based Approach

Urban floods are becoming increasingly common worldwide, and Ankara is no exception. With rapid urbanization, climate change, and aging infrastructure, understanding where floods are most likely to occur has become essential for city planners, policymakers, and disaster‑management teams.

This article summarizes a GIS-based study that applies the Modified Analytical Hierarchy Process (M-AHP) to assess flood susceptibility across Ankara—highlighting high-risk zones and supporting smarter urban planning.

Why Flood Susceptibility Mapping Matters

Floods cause major damage to communities, particularly in dense metropolitan areas. Effective flood susceptibility mapping supports:

Urban planning and zoning
Infrastructure and drainage system design
Emergency response planning
Climate-adaptation strategies

Given rising rainfall intensity linked to climate change, cities need proactive tools to understand and reduce risk before disasters happen.

Methodology Overview — Why M-AHP?

The Modified Analytical Hierarchy Process is an enhanced decision-support method that:

Reduces expert bias
Supports multi-criteria evaluation
Integrates seamlessly with GIS
Handles complex natural hazard parameters effectively

This makes M-AHP well-suited for urban flood assessments.

Data Sources Used

1. High-Resolution Photogrammetric Data

Aerial imagery from 2008 and 2015 (30 cm GSD) was used to create:

Digital Surface Models (DSM)
Digital Terrain Models (DTM)
Orthoimage mosaics

These datasets underpin topographic and hydrological analysis.

2. Vector Data (TOPOVT)

Includes rivers, lakes, seasonal streams, and dry drainage channels—critical for modeling natural flow paths.

3. Geological and Environmental Data

Lithology from national geological datasets
Land cover derived from Landsat 8 imagery (August 2018)

These help determine permeability, infiltration, and surface-runoff characteristics.

Key Conditioning Factors

The analysis considers multiple factors influencing flood behavior:

Slope gradient: flatter terrain → higher risk
Topographic altitude: lower elevations → higher risk
Flow accumulation: concentrated upstream flow → higher risk
Distance to drainage channels: closer proximity → higher risk
Topographic Wetness Index (TWI): water accumulation indicator
Lithology: permeable units reduce susceptibility
Land cover: urban and industrial areas increase runoff

Each factor was scored and integrated within the M-AHP framework.

Results: High-Risk Flood Zones in Ankara

The model classified the city into five susceptibility levels: very low, low, moderate, high, and very high.

High-susceptibility areas include:

Yenimahalle & Etimesgut

Broad alluvial valley floors
High accumulation potential

Çankaya

Narrow valley bottoms
Increased concentration of surface runoff

These regions showed logical correlation with DTM-based terrain features, reinforcing model reliability.

Implications for Urban Planning

The flood susceptibility map provides actionable insights for:

Infrastructure upgrades
Building-permit regulations
Drainage planning
Emergency response prioritization

As Ankara expands, incorporating these maps into long-term planning is essential for reducing disaster risk.

Future Work

Enhancing the model may include:

Higher-resolution datasets
Sentinel-1 & Sentinel-2 integration
Validation with real flood events
Localized sub-regional susceptibility mapping

These refinements can improve prediction accuracy and support climate-resilient development.

Conclusion

The M-AHP approach offers a powerful, cost-effective method for flood susceptibility assessment in urban environments. For Ankara, this model provides valuable guidance that can help city officials and planners reduce vulnerability and strengthen long-term resilience.

Prepared by Burhan Sözer
Software Engineering & GIS Solutions