Lost Waterways: Clues from Digitized Historical Maps of Manila and Other Philippine Cities

TL;DR

This study uses digitized historical maps aligned with Google Maps to identify and verify lost bodies of water in Philippine cities, revealing potential flood and liquefaction hazards and their impact on local communities.

Contribution

It introduces a method for locating lost waterways through map georectification and field validation, providing new insights into urban flood risks and historical waterway changes.

Findings

Identified previously lost waterways in multiple Philippine cities.

Confirmed the presence of new and existing water bodies affecting urban areas.

Documented impacts of waterway changes on flooding and local communities.

Abstract

We search for lost bodies of water in the cities of Manila, Tacloban, Iloilo, Cebu, Davao, and Naga by aligning their digitized Spanish-era and American-era maps to Google maps. These vanished ancient waterways can either become flooding hazards in case of extreme weather events, or liquefaction hazards, in case of earthquakes. Digitized historical maps of the cities were georectified, overlaid on current Google maps, and checked for potential missing bodies of water. Inspection through field visits and interviews with locals were conducted to verify the actual status of suspected sites. The validation identified lost, found, and even new bodies of water. There was also evidence of affected buildings, rainless flooding, and a new normal for the meaning of flooding among frequently inundated residents.