Saylorville Lake Flood Facts

Saylorville Dam Quick Stats

Construction: 1965-1977

Type: Earth-filled embankment

Length: 6,750

Height: 105 feet

Normal Pool Elevation: 836 msl

Flood Storage Pool: 890 msl

Maximum Dam Outflow: 21,000 cfs

Federal Cost: est $130.1 million

Damages Prevented (thru 2008):

estimated $181.9 million

Damages prevented in 1993 flood: estimated $113 million

Before the Dam

Record floods on this stretch of the Des Moines River occurred in 1947 and 1954. A total of 500 people were forced from their homes in 1947 and two people drowned. In 1954 1,800 people were forced from their homes.

In 1953 nine possible dam sites were studied. Six of these sites were on the Des Moines River and three on the Raccoon. The results recommended the construction of a flood control reservoir at the site of the Saylorville Dam.

Original design of the Saylorville Project was to handle a hypothetical flood including a lake level at 907 msl and flows of 162,000 cfs. This is the Probable Maximum Flood (PMF).

Saylorville Dam Control Tower in 1993 flood

1984 Flood

This was the first time the spillway operated. It performed as designed and has continued to do so since then. The lake level reached a maximum of 889.35 msl on June 22. This is 53 feet above the normal conservation pool. Water flowed over the spillway for a total of 14 days between June 18 and July 4.

Max. Inflow = 38,000 cfs on June 2
Max. Outflow = 29,000 cfs on June 22

Saylorville Outlet Channel at 13,500 cfs. The river is at 801 msl in spring 2001.

1991 Flood

Water flowed over the spillway for 11 days between June 6 and June 17. The lake reached a maximum level of 889.26 on June 9. The was 53 feet above the conservation pool.

Max. Inflow = 38,000 cfs on June 6
Max. Outflow = 26,000 cfs on June 10-11

The Spillway

(Located on the west side of the dam)

The spillway is a 430 feet wide concrete structure followed by an earthen channel. Water will begin flowing over the spillway when the lake level reaches 884 msl. The average slope on this stretch of the Des Moines River is 2.5 feet per mile. The drop from the top of the spillway wall to the area where it meets the Des Moines River is 80 feet in less than a mile. The force and speed of the water flowing over the spillway during the flood of 1984 created a "gorge" revealing many layers of bedrock that had never before been exposed in the Midwest . Geologists came from across the U.S. to see the many unique fossils and casts of prehistoric trees. Unfortunately, most of these were destroyed by vandalism. Today, there are still unique layers and fossils to be seen in the area as each use of the spillway reveals new sections of the many layers.

1993 Flood #1:

The lake level increased from 836 msl on March 25 to 882 msl on April 12. That's an increase of 46 feet in just 18 days! The water flowed over the spillway for nine days between April 22 and May 1 with a maximum lake level of 886 msl on April 27.

• Max. Inflow = 45,000 cfs • Max. Outflow = 21,000 cfs

1993 Flood #2:

The lake level reached the spillway and began flowing over on June 17. The lake reached its maximum flood control pool of 890 msl on July 10 and reached 55 feet above conservation pool (836 msl) on July 15. The water flowed over the spillway for 42 days. Continuous outflows of over 21,000 cfs occurred for 46 days! All recreation areas were closed on July 11 due to the shut down of the water supply from Des Moines Water works which was inundated by the Raccoon River .

• Max. Inflow = 61,000 cfs • Max. Outflow = 45,000 cfs

The Saylorville Dam operates in conjunction with Lake Red Rock to minimize downstream flooding on the Des Moines River, and eventually the Mississippi River . Since 1977, operation of Saylorville Reservoir has resulted in an estimated flood damage savings of $181.9 million to the city of Des Moines and areas below the reservoir. In addition, the summer and winter recreational, interpretive, and conservation activities at Saylorville Lake have brought much more than just a monetary value to the area and its visitors.