Floods of 1986 and 1990 in the Raccoon River Basin, West-Central Iowa, HR-140, 1992

Water-surface-elevation profiles and peak discharges for the floods of 1973 and 1979 are compared to those of 1986 and 1990 in the Raccoon River basin, west-central Iowa. The profiles illustrate the 1979 and 1986 floods on the Raccoon, South Raccoon, and Middle Raccoon Rivers, the 1973 and 1986 floods on Walnut Creek, and the 1986 flood on Willow Creek and Mosquito Creek. The 1986 flood is the largest on record at U.S. Geological Survey streamflowgaging stations on the Middle Raccoon River tributary at Carroll, Middle Raccoon River near Bayard, Middle Raccoon River at Panora, and Walnut Creek at Des Moines. The 1990 flood discharge is the largest on record at U.S. Geological Survey crest-stage gaging stations on Hardin Creek near Farlin and on East Fork Hardin Creek near Churdan. The flood history given in this report describes rainfall conditions for floods that occurred during 1986 and 1990. Discharge for the 1990 flood on East Fork Hardin Creek near Churdan was 1.01 times larger than the 100-year recurrence-interval discharge.

Floods of July 19-25, 1999, in the Wapsipinicon and Cedar River Basins, Northeast Iowa, HR-140

Severe flooding occurred during July 19-25, 1999, in the Wapsipinicon and Cedar River Basins following two thunderstorms over northeast Iowa. During July 18-19, as much as 6 inches ofrainfall was centered over Cerro Gordo, Floyd, Mitchell, and Worth Counties. During July 20-21, a second storm occurred in which an additional rainfall of as much as 8 inches was centered over Chickasaw and Floyd Counties. The cumulative effect of the storms produced floods with new maximum peak discharges at the following streamflow-gaging stations: Wapsipinicon River near Tripoli, 19,400 cubic feet per second; Cedar River at Charles City, 31,200 cubic feet per second (recurrence interval about 90 years); Cedar River at Janesville, 42,200 cubic feet per second (recurrence interval about 80 years); and Flood Creek near Powersville, 19,000 cubic feet per second. Profiles of flood elevations for the July 1999 flood are presented in this report for selected reaches along the Wapsipinicon, Cedar, and Shell Rock Rivers and along Flood Creek. Information about the river basins, rain storms, and flooding are presented along with information on temporary bench marks and reference points in the Wapsipinicon and Cedar River Basins.

Floods of May 17-20, 1999, in the Volga and Wapsipinicon River Basins, Northeast Iowa, HR-140

Record flooding occurred May 17-20, 1999, in the Volga and Wapsipinicon River Basins following thunderstorm activity over northeast Iowa. On Sunday, May 16, between 6 and 8 inches of rain fell during a 24- hour period over portions of Bremer, Butler, and Fayette Counties. Highest rainfall during this 24-hour period was 8.3 inches recorded north of Oelwein in southwest Fayette County. A peak discharge of 29,800 cubic feet per second in the Volga River at Mederville, 53,900 cubic feet per second in the Turkey River at Garber, and 31, 100 cubic feet per second in the Wapsipinicon River at Independence set new peak discharge records. The peak discharge at Garber was greater than a theoretical 500-year flood, and the peak discharge at Independence was the equivalent of a 90- year flood. Information about the basins, rain storms, flooding, and a profile of high water marks are presented for selected intervals along the Volga River, Wapsipinicon River, Crane Creek, Little Wapsipinicon River, and Otter Creek.

Flood of June 15-17, 1998, Nishnabotna and East Nishnabotna Rivers, Southwest Iowa, HR-140

Record flooding occurred June 15-17, 1998, in the Nishnabotna and East Nishnabotna River basins following severe thunderstorm activity over southwest Iowa. More than 8 inches of rain fell over a large part of Cass County. The rain gage at Atlantic, Iowa recorded a 24-hour total rainfall of 13.18 inches, which established a new official State record for the greatest amount of rainfall in a 24-hour period. The peak discharge was 41,400 cubic feet per second in the East Nishnabotna River near Atlantic, 60,500 cubic feet per second in the East Nishnabotna River at Red Oak, and 65,100 cubic feet per second in the Nishnabotna River above Hamburg. The peak discharge at Atlantic was greater than the theoretical 200-year flood and the peak discharges at Red Oak and Hamburg were greater than the respective theoretical 500-year floods. Information about the basin, the rain storms, the flooding, and a profile of high water marks at selected intervals along the Nishnabotna and East Nishnabotna Rivers are presented in this report.

Evaluation of Crushed Limestone Rock as a Mulch Material, HR-171, 1975

Earthen fills and back slopes resulting from highway building and other construction projects pose problems with respect to erosion stabilization and establishing vegetation cover. Sediments from such slopes create stream pollution while the erosion itself results in maintenance problems. Furthermore, adverse conditions aggravated by erosion prevent satisfactory establishing of vegetative cover. A dense vegetative cover is very effective in controlling erosion but even with optimum weather and soil conditions there is a delay of about 10 weeks between seeding and the establishment of a vegetative cover. Under actual field conditions, 3 months to a year may elapse between completion of construction and establishment of a vegetative cover. A research project was initiated early in 1974 to determine the effectiveness of a rock mulch of crushed limestone aggregates in controlling soil losses on highway construction back slopes in Iowa and to find the influence of such treatments on stand establishment of grasses and legumes.

Experimental Use of Calcium Magnesium Acetate, Addendum, HR-253, 1984

The Iowa Department of Transportation Materials Laboratory personnel developed a process to produce a road deicer consisting of sand grains coated with calcium magnesium acetate (CMA). Research project HR-253 was established to explore commercial production of the CMA/sand deicer by an independent contractor. About 60 tons of the deicer was produced at a ready-mix concrete facility and evaluated in the field during the 1983-1984 winter season. The initial contracted production of CMA/sand deicer under research project HR-253 identified two major problems: (1) excessive unreacted lime in the final product, and (2) formation of spherical lumps within the product requiring subsequent size reduction. It was recommended in the HR-253 report that additional deicer be produced as a continuation of the project in order to address these problems and further develop the production process. A contract was negotiated with W. G. Block Co. to produce and deliver 50 tons of additional deicer. This addendum report covers this production effort including descriptions and results of all modifications of equipment and process procedures used.

A Generalized Model Study of Scour Around Bridge Piers and Abutments, HR-24, 1953

Four classes of variables are apparent in the problem of scour around bridge piers and abutments--geometry of piers and abutments, stream-flow characteristics, sediment characteristics, and geometry of site. The laboratory investigation, from its inception, has been divided into four phases based on these classes. In each phase the variables in three of the classes are held constant and those in the pertinent class are varied. To date, the first three phases have been studied. Typical scour bole patterns related to the geometry of the pier or abutment have been found. For equilibrium conditions of scour with uniform sand, the velocity of flow and the sand size do not appear to have any measurable effects on the depth of scour. This result is especially encouraging in the search for correlation between model and prototype since it would indicate that, primarily, only the depth of flow might be involved in the scale effect. The technique of model testing has been simplified, therefore, because rate of sediment transportation does not need to be scaled. Prior to the establishment of equilibrium conditions, however, depths of scour in excess of those for equilibrium conditions have been found. A concept of active scour as an imbalance between sediment transport capacity and rate of sediment supply has been used to explain the laboratory observations.

Sieve Analysis of Combined Aggregate Samples by Different Test Methods, MLR-84-05, 1982

This past winter the sieve analysis of combined aggregate was investigated. This study was given No. 26 by the Central Laboratory. The purpose of this work was to try and develop a sieve analysis procedure for combined aggregate which is less time consuming and has the same accuracy as the method described in I.M. 304. In an attempt to use a variety of aggregates for this investigation, a request was made to each District Materials Office to obtain at least 3 different combined aggregate samples in their respective districts. At the same time it was also requested that the field technician test these samples, prior to submitting them to the Central Laboratory. The field technician was instructed to test each sample as described in method I.M. 304 and also by a modified AASHTO T27 method which will be identified in the report as Method A. The modified AASHTO Method A was identical to T27 with the exception that a smaller sample is used for testing. The field technicians submitted the samples, test results and also comments regarding the modified AASHTO procedure. The general comments of the modified AASHTO procedure were: The method was much simpler to follow; however, it took about the same amount of time so there was no real advantage. After reviewing AASHTO T27, T164, I.M. 304 and Report No. FHWA-RD-77-53 another test method was purposed. Report No. FHWA-RD-77-53 is a report prepared by FHWA from data they gathered concerning control practices and shortcut or alternative test methods for aggregate gradation. A second test method was developed which also was very similar to AASHTO T27, The test procedure for this method is attached and is identified as Method B. The following is a summary of test results submitted by the Field Technicians and obtained by the aggregate section of the Central Laboratory.

Reuse of Lime Sludge from Water Softening and Coal Combustion Byproducts, TR-459, 2004

Disposal of lime sludge remains a major challenge to cities in the Midwest. Disposal of lime sludge from water softening adds about 7-10% to the cost of water treatment. Having effective and safe options is essential for future compliance with the regulations of the State of Iowa and within budget restrictions. Dewatering and drying are essential to all reuse applications as this affects transportation costs and utility. Feasibility tests were conducted on some promising applications like SOx control in power generation facilities that burn coal, replacement of limestone as an ingredient in portland cement production, dust control on gravel roads, neutralization of industrial wastewater pH, and combination with fly ash or cement in construction fill applications. A detailed report and analysis of the construction fills application is presented in the second half of the report. A brief discussion of the results directly follows.

Case Study of Seasonal Variation in the Subgrade and Subbase Layers of Highway US 20, TR-516, 2008

Seasonal variations in ground temperature and moisture content influence the load carrying capacity of pavement subgrade layers. To improve pavement performance, pavement design guidelines require knowledge of environmental factors and subgrade stiffness relationships. As part of this study, in-ground instrumentation was installed in the pavement foundation layers of a newly constructed section along US Highway 20 near Fort Dodge, Iowa, to monitor the seasonal variations in temperature, frost depth, groundwater levels, and moisture regime. Dynamic cone penetrometer (DCP), nuclear gauge, and Clegg hammer tests were performed at 64 test points in a 6-ft x 6-ft grid pattern to characterize the subgrade stiffness properties (i.e., resilient modulus) prior to paving. The purpose of this paper is to present the field instrumentation results and the observed changes in soil properties due to seasonal environmental effects.

Methods for Estimating Annual Exceedance-Probability Discharges for Streams in Iowa, Based on Data through Water Year 2010, TR-519, 2013

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 exceedanceprobability 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 leastsquares 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. Average standard errors of prediction range from 31.8 to 45.2 percent for flood region 1, 19.4 to 46.8 percent for flood region 2, and 26.5 to 43.1 percent for flood region 3. The pseudo coefficients of determination for the generalized leastsquares equations range from 90.8 to 96.2 percent for flood region 1, 91.5 to 97.9 percent for flood region 2, and 92.4 to 96.0 percent for flood region 3. The regression equations are applicable only to stream sites in Iowa with flows not significantly affected by regulation, diversion, channelization, backwater, or urbanization and with basin characteristics within the range of those used to develop the equations. These regression equations will be implemented within the U.S. Geological Survey StreamStats Web-based geographic information system tool. StreamStats allows users to click on any ungaged site on a river and compute estimates of the eight selected statistics; in addition, 90-percent prediction intervals and the measured basin characteristics for the ungaged sites also are provided by the Web-based tool. StreamStats also allows users to click on any streamgage in Iowa and estimates computed for these eight selected statistics are provided for the streamgage.

Evaluation of Design Flood Frequency Methods for Iowa Streams, TR-533, 2009

The objective of this project was to assess the predictive accuracy of flood frequency estimation for small Iowa streams based on the Rational Method, the NRCS curve number approach, and the Iowa Runoff Chart. The evaluation was based on comparisons of flood frequency estimates at sites with sufficiently long streamgage records in the Midwest, and selected urban sites throughout the United States. The predictive accuracy and systematic biases (under- or over-estimation) of the approaches was evaluated based on forty-six Midwest sites and twenty-one urban sites. The sensitivity of several watershed characteristics such as soil properties, slope, and land use classification was also explored. Recommendations on needed changes or refinements for applications to Iowa streams are made.

Improved Methods for Determining Wind Loads on Highway Sign and Traffic-Signal Structures, TR-559, 2007

The main objective of the proposed study is to use Computational Fluid Dynamics (CFD) tools to determine the wind loads by accurate numerical simulations of air flow characteristics around large highway sign structures under severe wind speeds conditions. Fully three-dimensional Reynolds- Averaged Navier-Stokes (RANS) simulations are used to estimate the total force on different panels, as well as the actual pressure distribution on the front and back faces of the panels. In particular, the present study investigates the effects of aspect ratio and sign spacing for regular panels, the effect of sign depth for the dynamic message signs that are now being used on Iowa highways, the effect induced by the presence of back-to-back signs, the effect of the presence of add-on exit signs, and the effect of the presence of trucks underneath the signs potentially creating “wind tunnel” effect.

Erosion Control on Highway Backslopes, HR-64, Progress Report, 1959

During 1959, research was continued by the Agronomy Department in cooperation with the Iowa Highway Commission on vegetative establishment and erosion control on highway backslopes (Project 1010). The work was continued at previously established sites and also several new experiments were initiated during the year. The work will be discussed for each separate experiment and location in this report.

Floods of July 12, 1972, March 19, 1979, and June 15, 1991, in the Turkey River, Northeast Iowa, HR-140, 1996

Water-surface-elevation profiles and peak discharges for the floods of July 12, 1972, March 19, 1979, and June 15, 1991, in the Turkey River Basin, northeast Iowa, are presented in this report. The profiles illustrate the 1979 and 1991 floods along the Turkey River in Fayette and Clayton Counties and along the Volga River in Clayton County; the 1991 flood along Roberts Creek in Clayton County and along Otter Creek in Fayette County; and the 1972 flood along the Turkey River in Winneshiek and Fayette Counties. Watersurface elevations for the flood of March 19, 1979, were collected by the Iowa Natural Resources Council. The June 15, 1991, flood on the Turkey River at Garber (station number 05412500) is the largest known flood-peak discharge at the streamflow-gaging station for the period 1902-95. The peak discharge for June 15, 1991, of 49,900 cubic feet per second was 1.4 times larger than the 100-year recurrence-interval discharge. The report provides information on flood stages and discharges and floodflow frequencies for streamflow-gaging stations in the Turkey River Basin using flood information collected during 1902-95. Information on temporary bench marks and reference points established in the Turkey River Basin during 1981, 1992, and 1996 also is included in the report. A flood history describes rainfall conditions for floods that occurred during 1922, 1947, 1972, 1979, and 1991.