Engaged residents working across political and property boundaries to create and sustain a healthy watershed.
Through collaboration, education and research, implement science- based policies and practices for flood mitigation, water quality improvements, natural resources protection and improved recreation while maintaining economic health.
1. Reduce flooding.
- Implement urban and rural best management practices (BMPs) to: Mitigate increases in runoff volumes and peak rates of flow caused by man-made alterations to the landscape ii. Reconnect Walnut Creek and tributaries with their adjacent flood plains iii. Reduce streambank and channel erosion iv. Improve physical habitat within the stream and adjacent flood plains and stream buffers v. Reduce flood damage overall and protect municipal infrastructure b. Promote policies and practices which lead to soil quality restoration on both urban and rural landscapes
2. Improve water quality, with an emphasis on sediment, nitrate, phosphorus and
- E.coli reductions. Improve effectiveness and consistency of enforcement of Stormwater Pollution Protection Plans b. Develop and implement a monitoring program to measure results and identify additional pollutants of concern c. Implement urban and rural BMPs to meet water quality standards, reduce sediment and allow water contact recreation.
3. Enhance recreation and public health.
- Phase improved stream accesses to coordinate with water quality and safety improvements b. Improve watershed-wide volunteer coordination/opportunities for habitat improvement projects c. Incorporate purposeful community arts initiatives for improved public engagement and education, as well as enhanced aesthetics d. Enhance/improve greenway development within the watershed (e.g., See upcoming Clive Greenbelt Master Plan for example) Use buffering to expand the watershed’s greenways network and connectivity of waterways and trails f. Implement BMPs to: i. Restore wetlands/natural areas ii. Expand native landscape cover and riparian areas iii. Improve wildlife habitat and remove invasive species iv. Promote healthy soils.
4. Deliver enriched conservation education and programming with emphasis on
- Refer to the BMP Matrix to see which water quality/quantity management, wildlife/habitat, urban and agricultural practices address these goals and the pollutants of concern. needs within the watershed. Implement the Education and Collaboration Plan included within this Watershed Plan (Chapter 11).
5. Support community vitality and maintain economic health through implementing multi-purpose projects producing benefits in public, natural resources and economic health that can be documented.
- Establish metrics for projects that identify appropriate scales to measure social, economic, and environmental costs and benefits for projects b. Identify BMPs with multiple benefits through use of this Watershed Plan’s BMP Matrix, particularly employing use of the Community Section where multi-purpose projects, citizen awareness and regional connections are emphasized.
6. Develop ongoing means for collaboration and implementation of effective
- Policies and practices, taking a consistent watershed and/or regional scale approach as much as practical. (Also see Chapter 11: Collaboration and Education Plan, and Chapter 9: Policy Recommendations). Priority policies for watershed-wide (and/or metro-wide) adoption include: Unified sizing criteria as described within the Iowa Stormwater Management Manual (ISWMM).
Subwatershed Case Studies
The Walnut Creek watershed covers an area of nearly 83 square miles.
It would take significant investments within an area of this scale to notice measurable improvements in water quality. This is the primary reason that certain subwatersheds have been selected for more intense study. Focusing efforts in these "case study" areas allows monitoring to better measure changes in water quality that result from localized improvements. This provides the opportunity to review results and make strategic adjustments which can be applied to improvements in other subwatershed areas. A secondary benefit of this approach is more precise modeling of the subject area, using information about land use, streambank conditions, gully formation and existing management practices at a higher level of detail than is practical to collect at the larger watershed scale.
One subwatershed was selected to represent a typical rural setting, another in a developed area and one in an area which is expected to experience rapid urban growth in the next few years. Four candidate subareas of each of these types were presented to the Walnut Creek WMA board for review, to establish a consensus on which ones were to be designated as case study subwatersheds. For each selected subwatershed, a specific plan has been developed to target expected sources of key pollutants (see map on page 136).
A more detailed review of each case study is included within an appendix to this plan.
Rural Case Study—Subwatershed 411
Location This area is located in the headwaters of Walnut Creek. This 6.5-square-mile area is generally located between Dallas Center and Grimes, with Highway 44 running east-west through the center of the area. This subwatershed has been divided into 18 smaller areas, or microwatersheds, for analysis.
Pollutant Sources More than 80% of this subwatershed is used for row-crop agricultural production. Over the past two years, these areas were primarily farmed either in a rotation of corn and soybeans, or planted as corn in each year.