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Consultant: D10 and D22 stream length reduced about half; board to examine targeted repairs
Summary
ISG reported that historical straightening has reduced stream length in drainage districts D22 and D10 by roughly 57% and 52% respectively and recommended targeted repairs (riprap alternatives, riffles, oxbows) and pursuing outside funding partners.
ISG presented an existing-conditions report for drainage districts D10 and D22 and recommended the board authorize concept-level repair options. The consultant said the systems, straightened in the early 1900s, have re-meandered, are experiencing bank sloughing and sedimentation, and have substantially shortened stream length compared with original plats.
The ISG presenter reported specific reductions: D22 was originally about 22.26 miles and is now about 9 miles (a 57% reduction); D10 was originally about 11 miles and is now about 6.3 miles (a 52% reduction). The presenter argued that natural alternatives (re-meanders, rock riffles, storage ponds/oxbows) could reduce long-term upkeep compared with repeatedly armoring banks. "They cut back and forth, and that's how they make maintain control and slow themselves down," the ISG presenter said, using a downhill-skier analogy to explain how meanders slow water velocity and reduce erosion.
ISG said it had begun conversations with potential funding partners including the state DNR, Nature Conservancy and Natural Heritage Foundation; these organizations might fund land purchases or habitat features but would need clearer numbers before committing. The board approved proceeding with concept-level options and instructed ISG to return with cost estimates and funding scenarios.
Provenance: topicintro SEG 896, topfinish SEG 1166.
