Stream assessment tools help identify watershed resource conditions
Thanks to cooperation from land owners and operators, ISA’s Environmental Programs and Nature Conservancy in Iowa staff, along with the Iowa Department of Natural Resources (IDNR), have been using Rapid Assessment of Stream Conditions Along Length (RASCAL) to assess in-stream and near-stream environments of Iowa’s streams and rivers. The RASCAL procedure and its results are intended to assist watershed groups in identifying priority areas for targeted conservation practices in and near streams and rivers.
Adam Kiel, Upper Des Moines and Raccoon River Basin coordinator with the IDNR, says RASCAL was developed five years ago.
“It was developed by the IDNR and IDALS-DCS to get a better handle on the physical conditions of streams in Iowa,” Kiel says. “The assessment is conducted using GPS-enabled handheld computers that store information based on the location in which it was collected.”
Examples of tools frequently used include:
- Tablet Computers for Watershed Assessment: About the size of a notebook, these computers can be taken out in the field to speed up the data recovery process. Data is electronically entered into the Geographic Information Systems (GIS) right in the field. It comes with GPS tracking and other software showing watershed assessment data, watershed boundaries, field boundaries and aerial color infrared photos. Users can mark the locations of existing conservation practices, gullies, adjacent land use, canopy cover and other points of interest. In-stream habitat, open feedlots, sediment basins, highly eroded areas, filter strips, terraces and more can be inventoried.
- Handheld GPS Units for Stream Assessment: Similar to the tablet, it assists with stream corridor and gully assessments. The GPS, with built-in GIS software, has one to three meter accuracy; it’s waterproof and drop-resistant with an all day battery and touch screen. Variables such as streambank stability, substrate, land cover and more can be logged to identify priority areas.
- Sediment Delivery Calculator: This computer-based tool from the IDNR simplifies the process of calculating sediment delivery reductions from conservation practices. It evaluates land cover types, soil erosion characteristics and landform region variables to calculate load restrictions achieved from implementing conservation practices.
- LiDAR: Light Detection and Ranging (LiDAR) is a process of scanning the earth with lasers from an airplane to obtain accurate evaluation data. LiDAR is accurate within eight inches of actual elevations, while current data has an accuracy of plus or minus five feet.
Before field surveys are conducted, permission must be granted by landowners. If granted, planning maps are developed to outline which stream segments will be assessed. Stream or river assessments are usually conducted on foot, or if possible, by boat or canoe, covering about three miles a day. Data are collected every 750 feet, and stream characteristics are summarized by segment.
“In the past, much emphasis has been placed on erosion and nutrient contribution from upland areas with little focus being placed on the stream channel itself,” Kiel says. “The RASCAL procedure helps watershed and water quality experts get a better handle on stream channel issues, such as streambank erosion and habitat loss.”
ISA’s Environmental Programs have been working with farmers in the Lyons, Buck and Lower Eagle sub-watersheds in the Boone River Watershed, and also the Fannys Branch and Willow Creek sub-watersheds in the Raccoon River Watershed.
ISA State Watershed Coordinator Todd Sutphin says over the decades, farmers have effectively cut erosion from fields and soil loss into waterways through conservation tillage practices, grassed waterways, buffer strips, contour farming and more upland practices. Yet, over many decades, sediment carrying phosphorous has accumulated in stream banks and beds. During extreme runoff events, this legacy phosphorous is re-suspended in the streams by stream bank slumping and scouring of streambeds. Therefore, strategies to address phosphorous in the water need to account for both effectiveness of upland conservation practices and stream corridor strategies.
“When you pull a water sample, especially during rain events when stream levels are higher, some watersheds are still experiencing high phosphorous levels,” Sutphin says. “A lot of this is the result of decades of soil loss that had already occurred, and much of the phosphorus rich sediments reside in the streambanks and streambed. When you get a high rain event and the streambed is churned up, or there is streambank erosion due to high flows, water samples collected during this period often show elevated phosphorus levels.
“In conducting the RASCAL, locations of eroding banks and concentrated flow, areas with limited bank vegetation and gullies are recorded, along with riparian zone cover and adjacent land use. The idea is to assess these conditions and isolate some of the high contributing areas to soil loss and try to implement strategies to address these concerns.”
Since RASCAL is conducted on private property, land owner cooperation is vital.
“Land owners have the option of walking with watershed experts as they conduct assessment,” Kiel says. “If a land owner decides they do not want the assessment conducted on their land, that section of stream will not be assessed.”
Kiel feels farmers may be interested to see what watershed experts have to say about a stream, both good and bad, as it flows through their property.
“Farmers should be commended for practices that promote a healthy stream system, but if problems are found, watershed experts can work with those land owners to find solutions through voluntary conservation practices, such as stream buffers or streambank stabilization.”
Keegan Kult, ISA watershed management specialist, says with land owner cooperation, the RASCAL will go a long way toward informing watershed planning, and will also strengthen chances of the watershed groups gaining additional funds to help pay for conservation practices. However, there is no silver bullet and integrated solutions must be implemented.
“There are numerous issues out there so it’s going to take a lot of different practices to address them all,” Kult says. “In order to achieve conservation goals and improve profitability, there have to be several complimentary practices working together. We can’t stop all soil erosion with just one practice, but with a multitude of practices, we can reduce the impacts of the soil erosion process.”
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