This summer, Impact7G has been working within Soldier Creek in Fort Dodge, Iowa to survey and restore the stream utilizing the Iowa River Restoration Toolbox. This work aims to create increased stabilization, reduce erosion, and enhance water quality within Soldier Creek by bringing the stream back to its natural state.
While everyone knows that rivers and streams move water, fewer people realize that this flowing water is also transporting sediment. In restoring a river to a more natural state, stream designers walk a razors-edge in balancing this sediment load: too little sediment (and too much stream power) can cause streams to downcut (degradation), while too much sediment can cause streambeds to fill-up (aggradation) – neither of which is typically considered “stable” in most Midwest streams.
To help see what is going on in terms of sediment transport, Impact7G completed a sieve analysis to identify Soldier Creek’s bedload distribution — the relative sizes of particles that are transported along the bed of the creek. Identifying the ranges and size of particles within Soldier Creek helps identify sedimentation processes within the stream, a function of erosion, transport, deposition, and consolidation and sorting. Once sedimentation processes are quantified, they can help inform stream restoration designs that balance sediment inputs and outputs, resulting in a healthier stream system.
Sieve analysis is a relatively simple process that assesses the particle size distribution of particles within a material by passing it through a series of sieves that become progressively smaller. Each sieve catches different sizes of particles and is later weighed. Once all sieves are weighed with their respective particle samples, the total weight of all samples is gathered, and the percentages of samples as part of the whole material can be calculated, determining the size distribution of particles within the material.
For our purposes, samples of the streambed of Soldier Creek were collected in several different locations and were passed through a standard set of sieves (7 In total). To help filter streambed sediments through the sieves in addition to shaking them, a hose was used to pass water through the sieves to allow sediments to fall into the smallest sieve possible. Water was later drained out of the streambed sediments to remove any excess weight that had been added during the sieving process. Individual sieves with their respective streambed sediment samples were then weighed to identify their percentage of the individual sample.
Impact7G has completed and is currently working on several stream restoration projects across the state of Iowa. Projects involving Soldier Creek in Fort Dodge and Bear Creek in Dyersville are currently underway and past projects include the Tedesco Environmental Learning Corridor in Ames and Clear Creek and the Clear Creek Trail in Coralville.
If you or your community have the need for stream restoration practices, natural resources enhancement, or are interested in pursuing future water quality improvement projects, Impact7G’s Watershed Planning and Design and Natural Resources departments would be happy to offer you our services.