Examination of Flood Characteristics at Selected Streamgages in the Meramec River Basin, Eastern Missouri, December 2015–January 2016 By Robert R. Holmes, Jr., Todd A. Koenig, Paul H. Rydlund, and David C. Heimann Overview methods (submersible pressure transducer, non-submersible pressure transducer, or non-contact radar). These obser- Heavy rainfall resulted in major flooding in the Mera- vations are recorded autonomously at a predetermined mec River Basin in eastern Missouri during late December programmed frequency (typically either 15 or 30 minutes) 2015 through early January 2016. Cumulative rainfall from dependent on drainage-area size and concomitant flashiness December 14 to 29, 2015, ranged from 7.6 to 12.3 inches of the stream. Although stage data are important, stream- at selected precipitation stations in the basin with flood- flow data are equally or more important for streamflow ing driven by the heaviest precipitation (3.9–9.7 inches) forecasting, water-quality constituent loads computation, between December 27 and 29, 2015 (National Centers for flood-frequency analysis, and flood mitigation planning. Environmental Information, 2016). Financial losses from Streamflows are computed from recorded stage data using flooding included damage to homes and other structures, an empirically determined relation between stage and damage to roads, and debris removal. Eight of 11 coun- streamflow termed a “rating.” Development and verification ties in the basin were declared a Federal Disaster Area of the rating requires periodic onsite discrete measurements (Nelson, 2016). of streamflow throughout time and over the range of stages The U.S. Geological Survey (USGS), in coopera- to define local hydraulic conditions. tion with the U.S. Army Corps of Engineers and St. Louis The purpose of this report is to examine character- Metropolitan Sewer District, operates multiple streamgages istics of flooding that occurred in the Meramec River along the Meramec River and its primary tributaries Basin in December 2015–January 2016 including peak including the Bourbeuse River and Big River (fig. 1). stages, peak streamflows, and the flood-frequency statis- The period of record for streamflow at streamgages in the tics associated with the peak flows. A comparison between basin included in this report ranges from 24 to 102 years the December 2015–January 2016 flood and a similar (table 1). Instrumentation in a streamgage shelter auto- flood in December 1982 in the Meramec River Basin also matically makes observations of stage using a variety of is included. Homes flooded by the Meramec River in Pacific, Missouri, December 29, 2015. Photograph by Doug Moore, St. Louis Post-Dispatch, used with permission. U.S. Department of the Interior Open-File Report 2016–1140 U.S. Geological Survey 2 Examination of Flood Characteristics in the Meramec River Basin, Missouri, December 2015-January 2016 90°30' Missouri Valley Park 07019130 # Eureka 07019000 91° Pacific # 38°30' # 07019300# Union 07016500 # 07017020 Arnold #07018500 M r i e s 91°30' r s v e i i v s R i Dittmer 2.1 WSW eus e R s rb i u c p o e B am p r i e R M i v er e Ownsville 6.7 S iv r R g i B Sullivan 07018100 #07014500 # #07015720 Vichy/Rolla National Airport 07013000 38° # Steelville 2 N Steelville Rolla Potosi St. James 10.1 SSE # #07017200 07010350 Caledonia 1.8 NNW 0 5 10 20 MILES 0 5 10 20 KILOMETERS Base from U.S. Geological Survey 37°30' 1:24,000 Watershed Boundary Dataset, 2010 EXPLANATION Meramec River Basin 07010350 # U.S. Geological Survey streamgage and number Bourbeuse River Basin National Climatic Data Center precipitation station Big River Basin and name Cities Main-stem Meramec River Basin Figure 1. Meramec River Basin including major tributaries—Bourbeuse River and Big River. Characteristics of December 2015–January 2016 Flooding in the Meramec River Basin 3 Characteristics of December 2015– streamgages, no peak streamflow during the December 2015– January 2016 flood exceeded the peak streamflow for the January 2016 Flooding in the Meramec period of record, but the peaks generally were ranked in the top five at the selected stations(table 1). The streamgages at River Basin which the December 2015–January 2016 flood did not rank in the top five of streamflow peaks during the period of record Flood Summary Data by Streamgage were in the upstream portion of the basin. These streamgages included the Meramec River near Steelville, Missouri, and the Streamflow hydrographs for December 20, 2015– Big River at Irondale, Missouri, but the December 2015 peaks January 7, 2016, at selected main-stem and tributary at these streamgages still ranked in the top 10 for peak stream- streamgages in the Meramec River Basin show the upstream flow during the period of record. to downstream increase in streamflow magnitude and the temporal progression of streamflow peaks in the basin(fig. 2). Table 1. Peak stage and streamflow data at selected There were peak stages during the December 2015–January streamgages in the Meramec River Basin for the flood of 2016 flood in the basin that exceeded the period-of-record December 2015–January 2016 (available online at http://dx.doi. peak stage at selected streamgages (table 1). Of these selected org/10.3133/ofr20161140). 70,000 0 180,000 0 0.02 1.07 0.08 07019000 0.16 0.5 160,000 60,000 07016500 Meramec River 1 0.62 Bourbeuse River 1 140,000 0.92 near Eureka, 50,000 1.34 Missouri at Union, Missouri 1.5 120,000 2 (precipitation from (precipitation from 40,000 2 100,000 2.72 3 30,000 2.5 80,000 3 60,000 4 20,000 3.5 40,000 3.51 5 10,000 4.11 4 20,000 5.28 0 4.5 0 6 90°30' 30,000 0 60,000 0 07015720 0.5 0.73 25,000 0.5 1.53 91° 0.21 0.19 0.5 Bourbeuse River near 1 38°30 # 50,000 0.71 1 High Gate, Missouri 1.5 91°30' # 07018100 20,000 40,000 (precipitation from Vichy/ 2 Big River near 1.5 Rolla national Richwoods, Missouri 15,000 2.34 2.5 30,000 (precipitation from 2 3 2.5 10,000 3.5 # 20,000 # # 2.65 4 3 5,000 10,000 4.5 3.5 4.31 38° 3.41 0 5 0 4 tion, in inches a 70,000 0 # # 07014500 30,000 0 ecipit 60,000 0.21 0.5 r Meramec River near 0.65 07017200 50,000 0.73 Sullivan, Missouri 1 25,000 0.5 (precipitation from Big River at 40,000 1.5 20,000 Irondale, Missouri 1 Daily p (precipitation from 30,000 2 15,000 1.35 Caledonia 1.8 NNW, 1.5 1.54 1.5 20,000 2.5 10,000 2 2.83 10,000 3 3.29 5,000 2.5 0 3.5 0 2.82 3 20,000 0 12/20 12/23 12/26 12/29 1/1 1/4 1/7 18,000 0.49 0.5 0.53 0.49 16,000 07010350 1 Meramec River at 14,000 1.5 EXPLANATION 12,000 Cook Station, Missouri (precipitation from 2 10,000 St. James 10.1 SSE, 2.5 8,000 6,000 3 3.5 4,000 3.81 3.14 2,000 4 Daily precipitation and value 0 4.5 0.71 12/20 12/23 12/26 12/29 1/1 1/4 1/7 Figure 2. Streamflow hydrographs and precipitation distributions for selected streamgages and precipitation stations within the Meramec River Basin, December 20, 2015–January 7, 2016. 4 Examination of Flood Characteristics in the Meramec River Basin, Missouri, December 2015-January 2016 Comparison of 1982 and 2015 Floods For the upstream streamgages on the Meramec and Bourbeuse Rivers (first three streamgages listed in table 2), The heavy rainfalls that occurred in December 2015 in the December 1982 peak stages were higher than the Decem- the Meramec River Basin were similar in timing and mag- ber 2015 flood stages as would be expected with higher nitude to those in December 1982, which also resulted in streamflows and when the hydrodynamic conditions of the widespread flooding in the basin (Sauer and Fulford, 1983). channel (which would affect the relation between stage and Both events were associated with an El Niño climatic pattern streamflow) have not changed appreciably between floods. (National Oceanic and Atmospheric Administration, 2016), The December 1982 peak stages at the upstream Bourbeuse which is characterized by warm ocean temperatures in the and Meramec River streamgages were 0.72 to 1.25 feet higher equatorial Pacific Ocean and increased rainfall across the than in December 2015. For the downstream streamgages on southern tier of the United States (Earth Systems Research each river (table 2), the 1982 flood peak stages were 0.51 to Laboratory, 2016). A comparison of peak stages and stream- 4.24 feet lower than the December 2015 flood, and the Decem- flows during the December 1982 and December 2015 floods at ber 1982 streamflows generally were lower than in December selected locations within the Meramec River Basin is shown 2015. The exception was the Bourbeuse River at Union, Mis- in table 2. The December 1982 flood peak streamflows were souri, streamgage with a peak stage that was 0.51 feet higher greater than the December 2015 flood peak streamflows at in December 2015 than in December 1982 despite a lower upstream Meramec River and Bourbeuse River streamgages peak streamflow. A higher peak stage for a lower peak stream- (first four streamgages listed intable 2), whereas the Decem- flow is the result of changing hydrodynamic conditions of ber 2015 streamflows were greater than December 1982 peak the channel, either from downstream backwater effects from flows at the Meramec River near Eureka and all Big River tributaries or the Meramec River, the timing of the flood wave, streamgages.