{"id":19355,"date":"2021-12-10t08:46:14","date_gmt":"2021-12-10t14:46:14","guid":{"rendered":"\/\/www.dicovercards.com\/?post_type=snyder-projects&p=19355"},"modified":"2023-07-10t14:28:51","modified_gmt":"2023-07-10t19:28:51","slug":"fourmile-creek-watershed-stabilization-and-water-quality-improvements","status":"publish","type":"snyder-projects","link":"\/\/www.dicovercards.com\/projects\/fourmile-creek-watershed-stabilization-and-water-quality-improvements\/","title":{"rendered":"fourmile creek watershed stabilization and water quality improvements"},"content":{"rendered":"

environmental changes result in increasing flood events<\/strong><\/span><\/h2>\n
\"machines<\/a>

the banks of fourmile creek are undergoing stabilization efforts utilizing rip-rap and vegetation.<\/p><\/div>\n

the\u00a0fourmile creek watershed<\/a>\u00a0in central iowa consists of nearly 80,000 acres of urban and agricultural communities. it\u2019s also home to over 80,000 residents. as this population has grown over many decades, this expansive watershed has become increasingly prone to regular flood events.<\/p>\n

these reoccurring floods have impacted numerous residents, resulting in frequent evacuations and the costly destruction of property. extensive efforts have been taken by several government agencies to minimize flooding<\/a> and enhance the overall water quality in the watershed. a seasoned team of engineers and environmental scientists from snyder & associates has been at the forefront of these efforts since 2006. through a multitude of projects, our team has made a significant difference in the health and safety of this critical water system.<\/p>\n

updating fourmile creek modeling & assessments<\/strong><\/span><\/h2>\n

initially, snyder & associates was commissioned to study the fourmile creek watershed to establish an accurate floodplain model to update the significantly outdated federal emergency management agency (fema) maps. our team of environmental scientists and engineers used hydrologic and hydraulic flood models, along with stream assessments, to evaluate the impact of flooding on future development and the impact that development may have on the watershed.<\/p>\n

hydrologic methods from previous studies only accounted for current land use while grouping the entire watershed into one basin. our team completed a\u00a0comprehensive review of both existing and future land use plans\u00a0to predict potential conditions in hydrologic models. each of these models divided the 118-square mile watershed into individual sectors to provide a more accurate analysis.<\/p>\n

peak flow rates developed through modeling were used to predict fourmile creek\u2019s response to flood events of varying magnitude and duration. a profile of the watershed patterns was established to create flood maps utilizing lidar data and arcgis software. these maps provide valuable information by increasing awareness of the likelihood of flooding and ultimately, reducing the devastating impacts floods can produce.<\/p>\n

streambank stabilization\u00a0increases watershed resilience<\/strong><\/span><\/h2>\n
\"rainstorm<\/a>

stream flooding in fourmile creek tributary a prior to stream stabilization improvements.<\/p><\/div>\n

in addition to extreme flooding issues, fourmile creek has a long history of erosion and poor water quality. many factors, such as above-normal precipitation and runoff volumes, impervious surfaces, and agricultural practices within the watershed contribute to the stream\u2019s degradation and erosion<\/a>. specifically, two tributaries of the creek located in ankeny \u2014 northeast tributary a and southeast tributary b \u2014 experienced extensive stream degradation and bank erosion after the 2008 floods and placed many properties and infrastructure at risk<\/a>.<\/p>\n

to address these individual tributaries, our team assessed over 7,400-feet of the stream before proposing improvements that would not only mitigate flooding but also complement the stream\u2019s natural protection, as well. this assessment, along with our intimate knowledge of the watershed, led to\u00a0sustainable design solutions.<\/p>\n

homeowner input, technical assessments, and an evaluation of alternatives were utilized to prepare conceptual designs for both tributaries using an integrated stream restoration approach. this approach provided cost-effective and aesthetic creek restoration through the combination of several techniques including vegetated buffers<\/a>, toe protection, graded floodplain benches, and weirs. combined, approximately 6,500-linear-feet of the stream was successfully stabilized at the conclusion of both projects.<\/p>\n

fourmile\u00a0creek watershed management authority\u00a0& stormwater management plan<\/strong><\/span><\/h2>\n

while the rehabilitation of the two tributaries drastically improved the creek\u2019s overall water quality, additional efforts were necessary to continue mitigating flooding, erosion, nutrient loading, and bacteria issues. to address these problems, local communities created the fourmile creek watershed management authority (fcwma) in 2012. this group focuses on collaborative work to address both flooding issues and water quality. snyder & associates was commissioned to study the region with the intent of improving the understanding of the watershed and preparing a\u00a0stormwater management plan<\/a>.<\/p>\n

our experts knew that appropriate mitigation had to account for a powerful, meandering alluvial stream that transports significant sediment load. in some cases, extreme events caused substantial channel changes due to high flow, debris jams, erosion, and sediment deposition. toe rock protection integrated with bendway weirs, floodplain benches, and native vegetation buffers were incorporated into the design. additional measures included establishing permanent easements and expanding polk county\u2019s adjacent conservation area which helped diversify stream habitat and increased wildlife access to the water.<\/p>\n

this management plan also addresses overall maintenance goals and responsibilities, budgetary costs, and phasing for the full development of the comprehensive system. additionally, potential regulatory tools, grants, and funding opportunities were outlined and adopted by all jurisdictions involved.<\/p>\n

fourmile creek\u00a0greenway master plan<\/strong><\/span><\/h2>\n
\"butterfly<\/a>

natural vegetation was incorporated during restoration to enhance wildlife ecosystems.<\/a><\/p><\/div>\n

a series of eight watershed goals aimed at reducing flooding and improving water quality were included in the plan to provide guidance. each goal was assigned subgoals and tasks to help track milestones and develop a schedule. the adoption of a greenway system, or master plan<\/a>, was one of the eight primary goals of the fcwma. this specific goal outlines practices, such as\u00a0native vegetation\u00a0re-establishment,\u00a0stream restoration, and wetland enhancements. the greenway master plan addresses these improvements, as well as potential recreation and education opportunities along approximately 10-miles of the creek.<\/p>\n

stakeholder input and thoughtful consideration of multiple elements are essential when 2022世界杯32强预选赛 and implementing a greenway system. during a 世界杯足球比赛预选赛 open house, our team gathered community input for the future of fourmile creek, which helped shape the plan\u2019s objectives.<\/p>\n

greenway master plan objectives:<\/p>\n