* Information and data here is considered preliminary and subject to revision unless stated otherwise. *
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This report summarizes 47 U.S. Geological Survey flood-profile reports that were published for streams in Iowa during a 50-year period from 1963 to 2012. Flood events profiled in the reports range from 1903 to 2010. The report summarizes flood-profile measurements, changes in flood-profile report content throughout the years, streams that were profiled in the reports, the occurrence of flood events profiled, and annual exceedance-probability estimates of observed flood events. A total of 94 stream reaches have been profiled in U.S. Geological Survey flood-profile reports. Floods were profiled for June flood events for 18 different years, followed by July flood events for 13 years, May flood events for 11 years, and April flood events for 9 years. Multiple large flood events exceeding the 2-percent annual exceedance-probability discharge estimate occurred at 37 of 98 selected streamgages during 1960-2012. Five large flood events were recorded at two streamgages in Ames during 1990-2010 and four large flood events were recorded at four other streamgages during 1973-2010. Results of Kendall's tau trend-analysis tests for 35 of 37 selected streamgages indicate that a statistically significant trend is not evident for the 1963-2012 period of record; nor is an overall clear positive or negative trend evident for the 37 streamgages.
Streamflow Characterization and Summary of Water-Quality Data Collection during the Mississippi River Flood, April through July 2011
From April through July 2011, the U.S. Geological Survey collected surface-water samples from 69 water-quality stations and 3 flood-control structures in 4 major subbasins of the Mississippi River Basin to characterize the water quality during the 2011 Mississippi River flood. Most stations were sampled at least monthly for field parameters suspended sediment, nutrients, and selected pesticides. Samples were collected at daily to biweekly frequencies at selected sites in the case of suspended sediment. Hydro-carbon analysis was performed on samples collected at two sites in the Atchafalaya River Basin to assess the water-quality implications of opening the Morganza Floodway. Water-quality samples obtained during the flood period were collected at flows well above normal streamflow conditions at the majority of the stations throughout the Mississippi River Basin and its subbasins.
Methods for Estimating Annual Exceedance-Probability Discharges for Streams in Iowa, Based on Data through Water Year 2010
A statewide study was performed to develop regional regression equations for estimating selected annual exceedance-probability statistics for ungaged stream sites in Iowa. The study area comprises streamgages located within Iowa and 50 miles beyond the State’s borders. Annual exceedance-probability estimates were computed for 518 streamgages by using the expected moments algorithm to fit a Pearson Type III distribution to the logarithms of annual peak discharges for each streamgage using annual peak-discharge data through 2010. The estimation of the selected statistics included a Bayesian weighted least-squares/generalized least-squares regression analysis to update regional skew coefficients for the 518 streamgages. Low-outlier and historic information were incorporated into the annual exceedance-probability analyses, and a generalized Grubbs-Beck test was used to detect multiple potentially influential low flows. Also, geographic information system software was used to measure 59 selected basin characteristics for each streamgage.
Regional regression analysis, using generalized least-squares regression, was used to develop a set of equations for each flood region in Iowa for estimating discharges for ungaged stream sites with 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities, which are equivalent to annual flood-frequency recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively. A total of 394 streamgages were included in the development of regional regression equations for three flood regions (regions 1, 2, and 3) that were defined for Iowa based on landform regions and soil regions.
As flooding continues in parts of Missouri, Iowa, Illinois, Wisconsin, Michigan, and Indiana due to heavy rainfall over the past seven days, the U.S. Geological Survey is maintaining its response efforts and preparing for continued flooding in the Northern Plains and upper Midwest.
So far this spring, USGS streamgages have measured approximately 17 peaks of record, and numerous flood peaks that have been the largest in more than 50 years. The USGS will be in flood response mode for the next several days as flooding continues down the Wabash and White Rivers in Indiana, the Illinois River in Illinois, and along the middle Mississippi River.
The USGS is also ready to deploy field crews to the Red River of the North Basin in North Dakota and Minnesota as air temperatures rise above freezing and snowmelt begins, and has installed seven rapid deployment gages at locations in the basin where streamflow data is needed but otherwise unavailable. Runoff and subsequent flooding is expected to begin this weekend, especially in Fargo, N.D., and Oslo, Minn.
Summary: Flooding in Eastern and South Central Iowa
Flooding continues and expand in eastern and south central Iowa with 23 streamgages above NWS flood stage and 6 streamgages above NWS major flooding levels. Crews continue to make discharge measurements and in some locations are having a difficult time accessing the streamgages due to flooded roadways. Multiple crews are out measuring streamflow and over road flow at several sites. Thirty high-flow measurements have been made since Wednesday afternoon with a number of check measurements made to confirm shifts; discharge measurements have also been made at 9 crest stage gages since the flooding began.
Old Man's Creek near Iowa City, IA 05455100 has had a temporary orifice line installed due to damage from the high flows. The Hach Nitratax real-time nitrate sensor at this site was lost when debris and high flow damaged the river line and nitrate sensor installation.
Community's in the flooding area continue to assess damage including a mudslide on the campus of the University of Iowa. Maximum 24 hr rainfall total occurred in North Liberty, Ia which recorded 8.3 inches in 24 hours.
Summary: Heavy rains impact streamflow in Iowa
The eastern half of Iowa is experiencing moderate flooding in a line from Dubuque to Chariton Iowa. Currently 17 gages are above NWS flood stage with a number of other gages very close to NWS flood stage. Rainfall totals (24 hours) in this area range from almost 3 inches at the Mississippi River at Dubuque, almost 6 inches at Coralville (Clear Creek) to 7" at the Chariton River nr Moulton, IA. This rain is falling in areas of saturated soils. Many roads in the Iowa City area have been closed due to the flooding.
Johnson County Iowa has issued a disaster declaration due to flash flooding http://thegazette.com/2013/04/17/johnson-county-reacts-to-flash-flooding/ Temporary flood protection (Tiger Dams) have been deployed by the City of Cedar Rapids along Indian Creek http://thegazette.com/2013/04/17/cedar-rapids-swinging-into-action-with-flood-preparation/
Crews from the Eastern Field Unit were out yesterday measuring high water and will be out today (and tomorrow) focusing on sites with flow above current ratings and crest stage gages.
Summary: Rivers in eastern Iowa are in moderate flood stage after 2-3 inches of rain on snow pack and frozen ground
Crews from the Eastern Field Unit of the USGS Iowa Water Science Center went into the field on Sunday March 10th to measure high flow and repair river orifice lines damaged by high flow. Eastern Iowa received 2-3" of rain starting late Saturday and through the day Sunday; this rain fell on the snow pack and frozen ground in this area of the state. Multiple crews went into the field Sunday to measure high flow and repair river orifice lines that were damaged by the high flow. Rivers in the Iowa, lower Des Moines, Cedar, Skunk, Upper Mississippi, and Turkey/Maqouketa Basins are above flood stage. Crews are out again today measuring high flow and continue to repair orifice lines damaged by the high flow. Multiple highwater measurements will be made and repairs have been and or will be made to 6 gages.
This report provides a description of the watershed, the thunderstorms, the flooding, and a profile of high-water marks measured at 20 locations along the South Skunk River.
Bayesian WLS/GLS Regression for Regional Skewness Analysis for Regions with Large Crest Stage Gage Networks
This paper summarizes methodological advances in regional log-space skewness analyses that support flood-frequency analysis with the log Pearson Type III (LP3) distribution. A Bayesian Weighted Least Squares/Generalized Least Squares (B-WLS/B-GLS) methodology that relates observed skewness coefficient estimators to basin characteristics in conjunction with diagnostic statistics represents an extension of the previously developed B-GLS methodology. B-WLS/B-GLS has been shown to be effective in two California studies. B-WLS/B-GLS uses B-WLS to generate stable estimators of model parameters and B-GLS to estimate the precision of those B-WLS regression parameters, as well as the precision of the model. The study described here employs this methodology to develop a regional skewness model for the State of Iowa.
Floods of July 23-26, 2010, in the Little Maquoketa River and Maquoketa River Basins, Northeast Iowa
Minor flooding occurred July 23, 2010, in the Little Maquoketa River Basin and major flooding occurred July 23-26, 2010, in the Maquoketa River Basin in northeast Iowa following severe thunderstorm activity over the region during July 22-24. A breach of the Lake Delhi Dam on July 24 aggravated flooding on the Maquoketa River. Rain gages at Manchester and Strawberry Point, Iowa, recorded 72-hour-rainfall amounts of 7.33 and 12.23 inches, respectively, on July 24. The majority of the rainfall occurred during a 48-hour period. Within the Little Maquoketa River Basin, a peak-discharge estimate of 19,000 cubic feet per second (annual flood-probability estimate of 4 to 10 percent) at the discontinued 05414500 Little Maquoketa River near Durango, Iowa streamgage on July 23 is the sixth largest flood on record.
An increase in flood magnitudes remains one of the most anticipated impacts of climate change. Land and water resource managers are asking questions about how to estimate future flood risks and develop effective flood mitigation strategies for the future. A new report published by U.S. Geological Survey scientists in the Hydrologic Sciences Journal looks at this potential linkage using historical records looking back 127 years through 2008 at 200 locations across the United States.
Year of The Flood
Devastating floods across much of the U.S. were severe and unrelenting during the spring and summer of 2011. When floods happen, USGS crews are among the first-responders. Often working in dangerous conditions, USGS scientists measure streamflow and river levels, repair and install streamgages, measure water quality and changes in sediment flow, and assess river changes. From flood forecasts to difficult decisions about flood management, science is critical for flood preparations and response.
Omaha World-Herald story on the USGS and the Missouri River Flood
Six New Streamflow Gages Available for Flood Forecasting
USGS recently installed six rapid-deployment streamgages to monitor flooding in the Missouri River basin. Four of the streamgages are located in Council Bluffs, two each on Mosquito Creek and Indian Creek. Another is located on Willow Creek near Logan, and the final is located near the intersection of Interstate 29 and State Highway V near Hamburg. Equipment installed at the sites include a non-contact radar sensor and data collection platform that records the height of the water surface at 15-minute intervals. The data are transmitted hourly via satellite and made available to the public via NWISWeb. The streamgages are operated in cooperation with the Omaha District of the U.S. Army Corps of Engineers. For more information, contact the Iowa Water Science Center at (319) 337-4191.
06610502 Indian Creek at Sylvan Drive at Council Bluffs, IA
06610504 Indian Creek at US Highway 275 at Council Bluffs, IA
06610645 Mosquito Creek at Yellow Pole Road at Council Bluffs, IA
06610658 Mosquito Creek upstream of I-29 at Council Bluffs, IA
403514095393101 Missouri River Overflow at I-29 near Hamburg, IA
Increased Discharge Measurements of Streamgages Located on the Missouri River
In response to flooding on the Missouri River, USGS is currently making weekly discharge measurements at streamgages located at Sioux City, Iowa, and at Decatur, Blair, Omaha, Plattsmouth, Nebraska City, Brownville, and Rulo, Nebraska. Discharge measurements are made three times per week on the Missouri River at Yankton, South Dakota. The data collected in the field are used to verify the current stage-discharge rating for each streamgage, and are also used by the National Weather Service and the U.S. Army Corps of Engineers in support of river forecasting and gate operations. For more information, contact the Iowa Water Science Center at (319) 337-4191.