Hidden Hydrology: How Lost Streams Shape Stormwater Challenges

This study explores how legacy hydrologic pathways and historical infrastructure decisions continue to influence stormwater challenges in Ohio. The study focuses on two case studies in Warren, Ohio, with persistent flooding problems: Woodland Avenue and Pine Avenue. Historically, these sites were the location of natural streams tributary to the Mahoning River. As Warren expanded, these streams were culverted or filled and subsequently omitted from contemporary FEMA floodplain maps and planning frameworks. Severe flooding has impacted critical facilities, including a youth center and key roadways, with conditions so extreme that vehicles were abandoned and frozen in the floodwaters for the winter. Case 1: Woodland Avenue Flood events near Woodland Avenue, situated atop the historic Red Run Stream, impacted Inspiring Minds, a facility supporting youth programs. After property damage caused by localized surface flooding, AECOM conducted an evaluation utilizing elevation data, historical maps, field investigations, and hydraulic modeling. The assessment examined sewer sizing, inlet capacity, rainfall intensity, and recurrence intervals to gauge flood susceptibility. Past investigations of this area have shown improper connections of stormwater laterals to sanitary lines, but AECOM ruled out sanitary sewer surcharging as a cause via residential dye testing. The flooding was a result of a 40-year rain event, lack of proper conveyance by the storm sewer, and geographic location. Hydraulic modeling of this event demonstrated the storm sewer system had available capacity, but the lack of inlets and storm conveyance to the interceptor contributed to ponding. Upon further review of record drawings and historical atlases, it was determined Woodland Avenue is one of the lowest elevation points in northeast Warren and was the original location of the Red Run Stream, the natural drainage location for a large part of the northeast corner of Warren, yet was not shown on modern flood maps after being culverted under a railroad in 1870. Case 2: Pine Avenue Historical records for Pine Avenue indicate the area once hosted a stream tributary to the Mahoning River, which was later altered dramatically for the construction of a large steel mill. At this time, the path of the river was straightened to increase the mill's footprint, and the tributary stream was replaced with a drainage tunnel. Post-industry, this infrastructure was not maintained, and the tunnel collapsed, cutting off the drainage pathway to the relocated river. This area receives stormwater flows for approximately 400 acres of the city, as stormwater sewers discharge to a nearby woodland. This woodland historically drained to the Mahoning river, first through the tributary stream, then through the tunnel. Without any available means of conveyance to the river, chronic flooding occurred, leaving Pine Avenue impassable with floodwaters over three feet deep. Despite the road being closed during flood events, vehicles would commonly get stuck in the floodwaters. Over the winter, many vehicles were frozen in the floodwaters. By revealing previously overlooked flood risks not captured by FEMA maps, the study provides a framework for Ohio communities facing similar challenges. They demonstrate that a deeper understanding of historical hydrology is crucial for informing future design and planning strategies.