Iowa River repeats its flood cycle

PHOTOS BY GARRY BRANDENBURG — The Iowa River ran low and slow for the past three years. Well, it was only a matter of time before Mother Nature's weather systems changed to place new circumstances in play to reverse too little water into too much water. Flooding was the hot topic this past week after last Tuesday's heavy rains, strong wind an tornadoes in some places. Too much heavy rain in the Iowa River watershed resulted in the Iowa River cresting last Thursday at about 19.3 feet, resulting in a temporary closure of Highway 330 south of Albion. The image of the Mann Wetland area on the floodplain was made before Highway 330 was closed. The reflective still waters at Timmons Grove (south) was made where the inundated access roadway to the boat ramp went under water. Camping at Timmons South was still open. And at Green Castle lake, the spillway intake tube was taking on a full load of excess water after well over five inches of rain totals were experienced in southern Marshall County.

The weather was our significant natural history moment this past week. A strong low pressure system wound itself into a tight ball of unstable air masses over the Midwest. Iowa took its share of severe storms that brought heavy rains, strong winds and several tornadoes last Tuesday.

In the wake of all the rain events, it was inevitable that too much water falling in too short of a time frame resulted in runoff into every waterway, small creek, large creek and ultimately into the Iowa River.

The Iowa River watershed area above Marshalltown is 1,532 square miles. Considering the storm pathways that placed lots of heavy rains above Marshall, Hardin, Franklin, and Wright counties, excess water runoff would impact every downstream location in some manner. The results are being felt now as we humans adapt and cope with the aftermath of weather events.

I made a brief tour of some parts of Marshall County on Tuesday afternoon, between rains, to inspect and look at the effects of too much water. A first stop was at Green Castle Recreation Area to view the 16 acre lake.

Yes, the lake level was up quite a bit but easily still within its capacity. In one of today’s images, the view shows the intake tube at the dam at Green Castle taking the excess water out in a controlled fashion. That is a very good thing.

It is very good that back in the 1980s, when the existing old dam was rebuilt and reinforced to modern standards, it was engineered to withstand just the type of weather event that happened this week.

Engineering plans called for substantial new backfill to reshape the dam itself to provide a wider base, a taller dam height and width, and an emergency waterway overflow area. A bentonite seal trench was part of the planning whereby in the deep soil layers under the dam face, it

was discovered that a bit of sandy soil elements allowed a bit of water percolation through the base layers of soil.

Bentonite clay products from Wyoming quarries were mixed by the contractor to create a slurry mixture. That slurry was backfilled into a deep trench and then covered with clay. The secret to this sealing process is a matter of physics; that bentonite expands by a factor of over ten times to force its way into all the surrounding soil pore spaces to create a seal.

Another design element was the intake tube itself, sized appropriately for Green Castle’s watershed and anticipated worst case scenarios of storm runoff waters. What you are looking at in today’s image is the drop spillway tube with its anti-vortex steel plate support.

The vertical portion of the intake is four feet in diameter and ten feet deep, all sitting on a huge concrete base. At the bottom of this ten foot tall drop pipe, is a 36 inch diameter opening that connects to over 70 feet of spiral galvanized metal pipe. That 70 feet of pipe is buried inside the dam and is there to allow a normal and safe way to maintain the lake water level. It works as designed.

It is safe. It is strong, and the flow of water exiting that tube was a rush of water crashing onto a deep bed of heavy rocks placed in such a way as to disperse and protect the soils from erosion. Those large rocks also work well to disperse energy when high water flows demand it.

Green Castle remains open for weekend activities, shelter house use, volleyball games, fishing, hiking around its one mile perimeter shoreline, bison viewing, or to look for yourself as the water flows into the intake pipe. Enjoying the outdoors is a summer time treat.

Green Castle waits for your visit.


A mid week stop by this scribe had me inspecting the boat ramp access roadway at Timmons Grove south. It was under water slightly last Wednesday morning. The river had not crested at that time, so more water was coming from upstream and backing up behind the Highway 330 grading.

Water did ultimately fill enough to overtop the highway necessitating its temporary closure. The image shows nice calm reflective water surfaces near the north end of the Timmons Grove campground loop roadway.

The access roadway to the boat ramp is hidden under those calm waters. This has happened before, and it will happen again. Given enough time for the river level to fall, the access roadway will reappear, probably with a bit of black silty sticky soil to deal with.

During flood times, the river is flowing fast and it is flat out dangerous! Keep off the river. Do not go kayaking or canoeing at this time.

The river water will show no mercy to people or other objects on, in or near the water. It is a power to recon with and respect to the utmost.

Be safe this weekend if you go boating on an Iowa lake where safe access and non flowing waters are quiet. Wear life jackets at all times while on the water in any watercraft.


My other image for today shows the floodplain backflow inundation waters south of Albion covering virtually all of the Mann Wetland area recently acquired by the Marshall County Conservation Board. Last fall, the area was seeded with a great diverse mixture of prairie and wetland-liking plants through a cooperative venture with the National Wildlife Refuge System. Personnel from two different NWR areas of Iowa brought their 4×4 utility vehicles, seed and seeders to the Mann area. The seed sat in place all fall, and through the winter and early spring, ready to germinate with warm weather. Just adding water is the next ingredient.

Mother Nature added water, lots of it. In time, those prairie and wetland plants will begin to prosper and grow. It will take several years for a complete picture to emerge as the area habitat dominates.

Jeremiah Manken, park maintenance supervisor for the MCCB, indicated that more development work is planned for the area this summer. A public parking lot will be rocked and will be located directly across from the Timmons north driveway.

That space will allow for public walk-in access primarily during fall hunting seasons, and this summer, boundary signs will be installed around the perimeter. Forest stand improvement work will be ongoing, and planning for the eventual Iowa River’s Edge Trail will take place to help coordinate lots of elements of that endeavor.


Meanwhile, other county conservation parks are open for outdoor adventures this holiday weekend. Memorial Day festivities and remembrances are in order for sure, and if part of your weekend also revolves around being outdoors, do by all means avail yourself of some

type of excursion to enjoy the natural world.

For example, new wildflowers can be found and identified at many forest sites such as Grammer Grove, Timmons Grove, the Iowa River Wildlife Area, Arney Bend Wildlife Area, Bear Grove, Three Bridges and the Grimes Farm Conservation Center. If grassland prairies are your interest, check out the Marietta Sand Prairie, Klauenberg Prairie Preserve, or the Wehrmann Prairie Preserve.

Fishing escapes can be addressed at Green Castle, or Sand Lake. Just a reminder, that the free fishing weekend is June 7, 8 and 9, during which no license is required. Fishing daily limits and possession limits do apply at all times.

Camping at Timmons (south) will most likely still be open since the majority of camp sites are not flood prone. However, some campsites will be too wet due to flooding to accommodate camping units. Planning ahead is a good idea.

Birding is an always open opportunity. Birds can be found everywhere. Look carefully. Listen intently. Explore habitats slowly and with respect. Let nature surround you with its clarity, wisdom and renewal.


Quote: “In every walk with nature, one receives far more than he/she seeks.” — John Muir, naturalist and explorer.

Garry Brandenburg is the retired director of the Marshall County Conservation Board. He is a graduate of Iowa State University with a BS degree in Fish & Wildlife Biology.

Contact him at:

P.O. Box 96

Albion, IA 50005


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