Two-Stage Ditches

What it is

Two-stage ditches are an in-stream conservation practice designed to enhance water management while providing multiple benefits. This practice involves a primary channel at the base with adjacent floodplain “benches” that are vegetated along the sides. The stream at baseflow can meander through the baseflow channel. The vegetated benches act as natural floodplains, increasing the capacity of the stream channel and allowing for sediment and nutrient capture.

How it helps

Improved floodplain connection: The two-stage ditch design enhances water management by improving the system’s capacity to handle high-water flows. During periods of heavy rainfall or snowmelt, the floodplain benches provide additional space to accommodate larger volumes of water, potentially reducing the risk of flooding at field edges.

Decrease precipitation driven runoff erosion: This approach stabilizes the ditch by spreading and slowing down the water flow, which helps to minimize runoff erosion, erosion downstream, and reduce the frequency of maintenance.

Reduce excess soil and nutrients in runoff: The vegetated benches can capture sediment particles and take up bioavailible nutrients from the runoff and in stream water during high loading events from heavy rainfall or snowmelt.

Maintenance

To maintain optimal function, it is important to regularly care for the vegetation on the benches and the buffer areas along the channel. This usually entails an annual mowing (prevent woody vegetation from establishing), where this material can be used for forage by the farmer. While sediment removal from the channel bottom is necessary, it typically needs to be performed less frequently compared to traditional drainage channels. Especially, when paired with land management practices such as cover crops, no till, and/or vegetated concentrated flow paths (critical area plantings, grassed waterways, etc.). Proper maintenance ensures the continued effectiveness and longevity of the two-stage ditch system.