Lowhead Dam Removals
in the Scioto Watershed

2019 by Alex Silbajoris, Friends of the Scioto River

Lowhead dam removal projects across the country are removing drowning hazards, improving paddling access and restoring streams to their natural state. Several recent dam removals have opened sections of the Scioto River and some of its tributaries, the Olentangy River and Alum Creek.

Usually the main reason for removing a lowhead dam is to remove the drowning hazard that it presents. They may not appear to be dangerous, but their danger is not visible. When approached from upstream, the dam itself might not be visible.

When water flows down the face of the dam, it keeps going down below the surface, and creates currents called "rollers" which tumble around below the dam, circle back up to the surface, and flow back to the foot of the dam, to be pulled down and around again. These trap any floating items like litter or human bodies, which tumble at the foot of the dam.

These currents capture swimmers or watercraft going over the dam, or sometimes people walking on top of the dam.

Removing a dam opens the section of stream upriver to access by canoes and kayaks. This is especially helpful in urban areas where stream bank access points might be far apart, or there may be none at all on a stetch of stream between two dams.

It also removes a barrier to fish migrating upstream, which opens more potential spawning grounds. Spawning fish seek shallow, flowing waters whose bottoms are not choked in silt deposits like those found in the slack pools above dams.

A common method for demolishing a dam is to atach a "hydraulic breaker" to the arm of an excavator. It strikes repeatedly like a jackhammer, powered by the excavator and pushed down by the machine's weight.

The excavator is safe below the dam because it can wade and move, and the water will not release in one great flush. The little skid loader can clear away broken concrete.

Note the yellow sediment control boom deployed to filter and trap sediment released by the work. This was the Fifth Avenue Dam removal project on the Olentangy River, in August 2012. That's State Rt. 315 on the bridges in the background.

An excavator fitted with a hammer chips away at the Fifth Avenue Dam

The breaker attchment shatters the concrete into crumbles and bigger chunks. Gravel-sized pieces fly away. The operator can flick it back and forth like a hand on a wrist, to pry at pieces and pull them down the face of the dam, where the skid loader can gather them.

Rather than cutting a deep notch, the operator chips off a few inches and moves farther along the dam, like eating corn on the cob. The water immediately flows through any new gap.

This was the Main Street Dam removal in downtown Columbus, in December 2014. The original reason for having a dam was to impound a supply of water for the Columbus Feeder Canal, part of the Ohio - Erie Canal system. This turned the Scioto and the lowest part of the Olentangy above the junction into a wide, shallow pool.

The removal was part of the Scioto Mile project, which lowered and narrowed the river to expose large areas of new parkland in the heart of downtown. This also opened river access for small watercraft to downtown, from the ramp on the pool above Greenlawn Dam. Now there are no obstructions between Greenlawn and the lowhead at the Dublin Road water plant on the Scioto, and the Dodridge Dam on the Olentangy.

The new parkland looked like a construction site. In front of COSI, Genoa Park gained more area. Fill was brought in and spread out to create green space below the amphitheatre, which once led to the water's edge. Before this, the performances had to be given from a stage floating on the river.

The old pool was nice for reflecting the skyline when seen from the west, but it served little other use. There was (and still is) a little-known boat ramp at the end of nationwide Blvd. but it was very seldom used, and weatercraft were almost never seen on the pool. There was a replica of the Santa Maria floating in a bay by the shore.

The effects of the removal extended beyond the Scioto Mile itself. The Olentangy River, above the junction with the Scioto, changed from a stagnant pool to a free-flowing stream braiding in riffles among bars of cobblestones. While a stream like this isn't conducive to boating, it's very inviting to fish.