Earthworks

Earthworks are the first step for many water quality improvement and surface soil erosion management practices.

Wetland reconstruction earthworks in progress.

Wetland Reconstruction

Unprofitable, poorly drained portions of crop fields may be well-suited for wetland restoration. These ecosystems are as biodiverse as tropical rainforests, and like the liver in the human body, they purify water and remove toxins. Many of Iowa’s native wetlands were fairly shallow and seasonally variable in depth, enabling water-loving prairie plants to grow throughout and maximize ecosystem services.

Accordingly, wetland earthworks create a shallow depression on the landscape where water flowing from surrounding land can be collected, held longer by the land, and filtered by a dynamic wetland ecosystem. The use of non-perforated drainage tile beneath the wetland ensures that constructing a wetland within a tile drained field does not hinder drainage in portions of the field that continue to be cropped.

Streambank Stabilization

Many streambanks can be restored through resloping, baffle construction using natural materials like wood and rock, and cedar revetments, which are simple, low-cost earthworks solutions. (See a cedar revetment installation here.) Solving erosion issues on larger streambanks requires equipment such as track hoe excavators.

In some cases where streams have been straightened, earthworks are used to remeander them. Remeandering streams slows the flow of the water to reduce streambank erosion and enable vegetation to filter out excess nutrients and other pollutants.

Swales capture rainfall and allow it to soak in, enabling tree crops to thrive on hilly ground, and preventing excess water at the base of the slope.

Saturated Buffers

The dense, deep-rooted vegetation buffering restored streambanks do an excellent job of filtering nitrogen, sediment and other pollutants from water that flows over the land. Depending on soil and land characteristics, some buffers may also be capable of filtering pollutants from agricultural drainage tile lines.

Saturated buffers intercept and redirect polluted tile water to be filtered through the buffer vegetation. They remove 99% of the nitrates from water in light to moderate rainfall events, and half of the overall nitrates in a typical year. Learn more about how saturated buffers work here.

Pocket ponds capture excess water from swales and hold it high on the landscape. They also provide habitat for amphibians and other wildlife.

Swales and Pocket Ponds

Swales and pocket ponds are natural water management techniques that are part of keyline design. These practices capture water and hold it on the landscape, enabling it to soak into the soil and be taken up by plant roots. Plant productivity increases, and soil erosion decreases when water moves more slowly across the landscape.