Floodplains Flood:
Controlling Floods As Nature Intended
By Tracy Carluccio, Deputy Director of Delaware Riverkeeper

» In 1996, heavy rainfall caused the worst flooding in years along the lower Neshaminy Creek, a tributary of the Delaware River. The rains, as much as nine inches in four hours, reawakened a long-abandoned plan to build a flood control dam along the creek. The Dark Hollow Dam had been proposed years before by the federal government and its local partner, Bucks County, Pennsylvania. The dam was to be a 450 foot wide, 56-foot high earthen dam. Its 610 acre reservoir would destroy high quality wetlands, a mature hardwood forest, critical native vegetative and wildlife habitat, a trout-supporting stream, and a prehistoric Native American village site.

Delaware Riverkeeper delved head first into a five-year long campaign to convince decision-makers that the solution to flooding was to remove people and structures from the floodplain, not destroy the creek. Riverkeeper organized the community, reviewed technical and scientific details, stimulated broad public input and inserted itself in the decision-making process with gritty perseverance. Delaware Riverkeeper had the science, but efforts to convince decision-makers to set aside their political message — an easy fix to flooding — proved a major challenge.

It was nature herself who overcame this impasse. In September 1999, Hurricane Floyd sent floodwaters through streets, over lawns and into homes along the Neshaminy. The floods destroyed buildings, closed bridges and highways throughout the region and resulted in millions of dollars in damages. The immense size of the flood sealed the fate of the Dark Hollow Dam, illustrating that the only way to truly protect flood victims is to move them out of the floodplain. Decision-makers and regulatory agencies began turning to the approach that Delaware Riverkeeper advocated all along: buy out the homes along the floodplain, safely relocate the families and commit to natural flood prevention.

Delaware Riverkeeper had spent four years advocating buyouts and identifying funding sources. Decision-makers and regulatory agencies now embraced the approach. It turned out that moving potential flood victims out of the floodplain was cheaper, and less controversial, than building a dam. Homeowners in the floodplain received fair market value and credit for several years of flood insurance premiums. In the end, 82 homes located in the 100-year floodplain were bought and demolished.

Delaware Riverkeeper continues to carry forward this learned experience. We fight new demands for structural solutions to flooding with the unassailable fact that floodplains flood. Floodplains are supposed to flood — this is part of the natural and beneficial life of a river. We advocate for the removal of structures and people from harm’s way and restoration of the floodplain to allow it to function as nature intended, as a naturally vegetated sponge that carries, absorbs and cleans stormwater. w

Fish and the Seminary Dam
» Wisconsin has long been a national leader in dam building. The world’s first hydropower project was completed here on the Fox River in 1882. While, the state officially counts more than 3,800 dams, the actual total including unregulated and abandoned dams is closer to 10,000. It is fitting then that Wisconsin is becoming a leader in dam removal.
In 1929, the Wisconsin Lutheran Seminary built a 24-foot timber and stone dam to create a pond on their 80-acre campus in Mequon, Wisconsin. In the 1950s the dam was rebuilt of concrete that, by 2000, had badly degraded. The dam wall leaned downstream and falling concrete exposed steel rebar beneath. Dredging of built-up sediment was long overdue and in the summer the pond was choked with algae and attracted nuisance Canada geese.
When the downstream Village of Thiensville began studying flood control in the Pigeon Creek watershed, their engineering consultants recommended removal of the dam. In spring 2006, Milwaukee Riverkeeper and Will Wawryzn from the state Department of Natural Resources met with the Seminary to present a plan for removal of the dam. Repairing the dam would cost more than $100,000, plus additional funds to dredge sediment from the pond. Removal, however, was estimated to cost $38,000, which the state would pay with funds from an environmental damage compensation fund. Repairing dams generally costs three to four times more than removing them. To their credit, the Seminary responded very positively not only to the economics, but to the ecological benefits of removing the dam.
Although we were worried about possible opposition to removing the pond, most public reaction was very positive. But there were obstacles. For example, the dam breach was pushed back almost a year so the Seminary could install fire hydrants. The fire department had relied on the pond as a water supply for firefighting.
Despite its small size, removing the Seminary Dam had a significant ecological impact — opening up 25 miles of stream and more than 600 acres of wetlands to migrating Steelhead, Salmon, Northern Pike, Sturgeon and Walleye.
The dam was slowly breached in spring 2007 and water quality downstream of the dam quickly rebounded. In fall 2008, state officials doing fish surveys witnessed Chinook Salmon and Steelhead Trout adults, fish that had likely made the 23 mile migration from Lake Michigan. They also witnessed Steelhead or Rainbow Trout smolts, juvenile fish, which likely spawned in the creek the previous spring. Riverkeeper is completing more intensive surveys with the goal of formally re-classifying the creek as a trout stream. In addition, Smallmouth and Largemouth bass have returned to the creek. We are hopeful other native fishes, such as the marsh spawning Northern Pike and Walleye, will return.
Riverkeeper and our volunteers will continue our in-stream work, restoring the meandering flow of the creek, stabilizing the new stream banks and replanting native vegetation. Milwaukee Riverkeeper will conduct water monitoring to document the return of Pigeon Creek. The Seminary has announced plans to upgrade trails adjacent to the restored creek and improve access for fishing.

Pigeon Creek drains 7,740 acres of farms and subdivisions before entering the Milwaukee River. Approximately 22 miles downstream, the Milwaukee River enters Lake Michigan. This suburban Milwaukee watershed contains 640 acres of intact wetlands, and another 350 acres of additional degraded wetlands that could be easily restored.
Milwaukee Riverkeeper water quality monitoring found that even this small dam increased water temperature and decreased oxygen levels, impairing the ability of the stream to support fish.