May 25, 2000

Comments of Darby Creek Association on Draft "Hellbranch/Clover Groff Ditch/Hamilton Ditch Greenway Plan" dated 4/28/00

Darby Creek Association (DCA) commends all involved with preparation of the Hellbranch Greenway Plan (HGP). The HGP draft is an invaluable document including much original content of great importance and an excellent summary of existing information. The HGP, if implemented in full, could be an important cornerstone of a comprehensive plan that includes all the affected jurisdictions. Such a comprehensive plan could be a model for the entire watershed.

DCA believes development in Western Franklin County is reaching a critical stage. If we do not adopt the HGP and other actions then this part of the Darby Watershed will have its biological integrity destroyed forever – with a seriously negative, possibly fatal, impact on the main stem of Big Darby Creek as the inevitable result.

DCA believes the document could be improved by greater emphasis on the biological, esthetic and recreational value of the entire Big Darby system. Hellbranch Run needs to be viewed as part of a more important whole that includes natural resources of national, if not global, significance. The fact that freshwater fish and mussels are the most threatened class of animals and the Darby Creeks have at least two Federally listed Endangered Species from this class means that protecting the water quality of this system is of paramount importance.

DCA agrees with the HGP that "the main threats to aquatic life now are agricultural and suburban stormwater runoff and habitat destruction." (p. 9 HGP) One of DCA’s objectives is to restore the quality of the Darby Creek ecosystem – the Hellbranch watershed provides the biggest challenge in this respect as "Clover Groff and Hamilton Ditches are two of the three worst tributaries, for water quality, to Big Darby Creek." (p. 9 – HGP) Given this situation, DCA recommends that all involved with HGP move immediately to a more comprehensive program that will include those watershed planning elements that are not included in HGP – especially Land Use.

Land Use planning must focus on what can be done to restore the Hellbranch watershed to a higher level of water quality. DCA looks with special concern on recent actions by government and private developers to fill in the floodplains. (p. 17 HGP) Franklin County, the City of Columbus and the City of Hilliard have all approved this type of highly irresponsible action in the past five years. Filling of floodplains in the Hellbranch watershed must stop.

Land Use planning must target a minimum level of impervious surfaces for the Hellbranch watershed. "Once a watershed has 10-15% of its area as impervious surfaces (paved or significantly compacted) the water quality of the stream will be significantly degraded by increased erosion in the stream, pollutants and warmer water temperatures that all reduce biodiversity." (p. 14 HGP) HGP also states that a typical subdivision has 30-40% impervious surface and commercial development has even more.

DCA suggests that the target for impervious surfaces in Hellbranch should be no more than 5%. This may provide sufficient buffer for the lower range (10%) where significant degradation occurs. Based on HGP’s data (40% impervious surface for a subdivision) this means no more than 15% of the Hellbranch land area should be developed. Currently, no estimate exists for how much Hellbranch land area has already been developed – no further development should be approved until such an estimate is developed and a target for the final level of development for the watershed is agreed upon.

The Filter Strip sketch (Pg 35a) is excellent (although this sketch refers to an appendix that is not present). Quantitative information in the sketches does not always match the text of the document. Sketches in the plan are good, more need to be added. For instance, road ditches running toward the stream should be diverted into a filter strip and not funneled directly into the stream. The road ditches currently running into the stream should be regraded away from the stream so that it drains into the filter strip. Bridges should be "plumbed" so that they drain into the filter strip.

DCA recommends that any mention of how developers should handle vegetation must be as specific as possible. Too often, developers interpret a statement that "trees" must be planted to mean that if he plants two trees (at least one of which will be dead in a year) he has done his job. Be as quantifiable as possible, developers build to numbers not images. Specify the density of trees in adjoining developments. For example, set a goal that developments should plant trees at a density of 70(?) trees per acre in the first 20 feet adjacent to the greenway and 50(?) trees per acre elsewhere. These trees should be native mixed mesophytic type trees. No conifers.

DCA recommends that the plan be more specific what trees should be planted in the riparian zone. Canopy: sycamore, swamp white oak, green ash, black walnut, buckeye, elm, hickory, basswood, cottonwood, etc. Understory: black willow (at stream edge), waffer ash, blackhaw, hawthorne, etc.

DCA supports greater emphasis on a "Natural Flow Regime." Ideally the water flow would emulate the historical natural flow. It would be desirable, but probably impossible, to know the actual flows prior to agricultural use, but most likely, wetlands in the area historically would seep a low flow of water continuously through the stream plus would limit the depth at floodstage. Today we tend to get high flows during flooding and almost no flow any other time. It is not the flooding, but the no flow periods which damage aquatic biodiversity because of low dissolved oxygen or dried up streams. Seepage from agricultural tile is one of the few sources of water in between storm events. Proposing agricultural water control management of tile could block this source of water. More, clean water in the stream during non-storm periods is preferable.

Existing HGP goals that DCA would like to highlight include:

Goal 1 – F: Develop uniform standards and a unified jurisdiction for all townships, Cities and County.

Goal 2: Restore the natural flow regime, protect the floodplain and reduce the impacts of flooding along Hellbranch Run and its tributaries.

Goal 3: Encourage and restore natural vegetation along Hellbranch Run and its tributaries.

DCA recommends the incorporation of an additional goal: Restore Hellbranch Run water quality to level found in main stem of Big Darby Creek upstream of its confluence with Hellbranch Run.

Goal 6. G.b: For stream segments that have woody vegetation completely removed, return stream to its correct meandering geomorphology, prior to revegetation. Meandering versus channelized streams provide greater floodplain capacity, thus prevent flooding. They also help to oxygenate the water and purify the water through aeration, plus increase aquatic habitats. (Applied River Morphology, Dave Rosgen, 1996)

Goal 6.D.c: Identify locations of agricultural tile and determine the wetland acreage required at each outlet for a standard stormwater event. Usually larger wetlands function better than smaller ones. Therefore, possibly divert the outlets into one large wetland. Either way, show these wetlands on the map. Emphasize multiple depth wetlands i.e. some permanent, others ephemeral. Typically the edges of the wetland are ephemeral with permanent and ephermal wetlands in the center. Each area has specific vegetation requirements.

Goal 7.A.b: DCA suggests that care must be taken with this area. This should not be seen as a blanket approval of all "log jam" removals. Many conservation agencies do not promote the removal of log jams. Logs in the water create aquatic habitat such as shallow pools and woody debris. Sometimes the erosion created in removing the logs does not offset the benefit. A criteria for selective removal of logs should be developed. DCA’s position is to not remove any log at or below the normal water line. Logs above the waterline provide minimum benefit except if the rootwad is still anchored in the bank. A comprehensive criteria should be developed in cooperation with NRCS, DNR-Scenic Rivers.