Ask Mr. Smarty Plants

We recommend grasses for controlling erosion because of their extensive fibrous root systems that serve to hold the soil in place.  However, I don't think just throwing grass seeds over the side of your bank is going to work very well.  The seeds need moisture to germinate.  If the moisture comes in the form of rain, it is likely to wash the seeds down the bank into the river before that have a chance to germinate and take root.  There are two possible solutions—an erosion control blanket or pneumatic compost/seed application.  The erosion-control fabric works by slowing the runoff water and allowing sediments to fall out rather than be washed away. Seeds are sown under the erosion-control material and grow up through the matting when they germinate. You can also insert plants into the soil by cutting through the matting. The roots of the plants that are growing through the erosion-control material anchor the soil to stop the erosion. If you use erosion-control blankets made of biodegrable material, they will eventually disappear leaving the plants to control the problem.  Many nurseries carry this erosion control fabric. 

The compost/seed application may be a bit more complicated and expensive than you had in mind since it does require a pneumatic blower, or some mechanical means, to spread the compost/seed mix. The US Composting Council offers information about suppliers of compost and compost technology, but I don't really know if this could be a do-it-yourself project.  You might check with a landscaping or environmental consulting company in your area who might have the machinery to do this to learn about the feasability and expense of applying the compost/seed mixture this way. You can find the names of Landscape Professionals and Environmental Consultants in your area that specialize in native plants by searching in our National Suppliers Directory.

Here are some grasses that should work on your bank.  However, since I don't know the specifics of how much sun/shade or the exact soil type you have there, you will need to compare those aspects of your site with the GROWING CONDITIONS given for each grass.

Andropogon virginicus (broomsedge bluestem)

Aristida purpurea (purple threeawn) is good for erosion control on banks.

Chasmanthium latifolium (Inland sea oats)

Muhlenbergia schreberi (nimblewill)

Panicum virgatum (switchgrass) grows on moist bluffs and stream banks.

Sorghastrum nutans (Indiangrass)

Tripsacum dactyloides (eastern gamagrass)

You can find more grasses to consider by doing a COMBINATION SEARCH in our Native Plant Database and choosing 'Iowa' from the Select State or Province category and 'Grass/Grass-like' from the Habit (general appearance) category.  You can also make choices from the Light requirement and Soil moisture categories.

Andropogon virginicus

Aristida purpurea

Chasmanthium latifolium

Muhlenbergia schreberi

Panicum virgatum

Sorghastrum nutans

Tripsacum dactyloides