9/28/2023 0 Comments Harris county flood mapThe Spring Creek watershed has over 83 miles of streams that were studied as part of the project and over 68 miles of the mainstream was modeled for the mapping program. Halff was selected by Harris County Flood Control District (HCFCD) to develop new floodplain maps for the Spring Creek watershed. The Federal Emergency Management Agency (FEMA) gave Harris County special permission to use new hydrologic and hydraulic modeling methods. The USGS produced 19 maps for six heavily flooded river basins, to include the Lower Brazos, Lower Neches, Pine Island Bayou, Sabine, San Jacinto and San Bernard, as well as the coastal areas of Corpus Christi, Port Aransas and Matagorda Bay.The purpose of the Modeling, Assessment and Awareness Project (MAAPNext) is to better understand flood risks within the 22 watersheds in Harris County, Texas, while using the latest adopted National Oceanic and Atmospheric Administration (NOAA) rainfall frequency values (Atlas 14, Volume 11) and improved modeling methods. These maps help identify areas most likely to experience flooding in any given year. FEMA uses this information to revise their Flood Insurance Rate Maps. The USGS conducts research on the physical and statistical characteristics of flooding, estimating the probability of flooding at locations around the United States. “Our crews are dedicated to making sure emergency managers have the information they need to help keep Texans safe – during the storm and into the future.” “The USGS had more than 100 employees from 16 states in the field working around the clock for about five weeks collecting flood measurements after the storm,” said Tim Raines, USGS Texas Water Science Center Director. This probability is also referred to as a 500-year flood. Thirty other USGS streamgages experienced flooding at levels with a 1 percent chance of occurring each year, also known as a 100-year flood. At two streamgage locations, scientists determined that the percent chance for flooding of this magnitude to happen in any given year was 0.2 percent. Record streamflow was measured at 40 USGS streamgages in Texas that have been in operation at least 15 years. The data and records will assist officials in updating building codes, planning evacuation routes, creating floodplain management ordinances, providing environmental assessments and planning other community efforts to become more flood-resilient. High-water mark data, along with flood flow information from USGS streamgages, were used to create 19 inundation maps to document the areal extent and depth of the flooding.įEMA requested time-perishable high-water marks, updated water-level records and Harvey inundation maps, which are key materials that will be used by state and local resource managers. Although parts of central Louisiana experienced Harvey related flooding, this report only documents the extent of flooding in southwest Louisiana along the Sabine River. USGS field crews collected 2,123 high-water marks in 22 counties in southeast Texas and three parishes across southwest Louisiana. In the immediate aftermath of Harvey, the USGS and FEMA initiated a study to evaluate the magnitude of flooding, determine the probability of future occurrence and map the extent of the flooding in Texas. Not only were rainfall totals exceptional during Hurricane Harvey, the area affected was also larger than previous events. history was during Tropical Storm Amelia in 1978, which left Texas Hill Country with 48 inches of rain. The second largest rainfall event recorded in continental U.S. Hurricane Harvey’s widespread 8-day rainfall, which started on August 25, 2017, exceeded 60 inches in some locations, which is about 15 inches more than average annual amounts of rainfall for eastern Texas and the Texas coast.
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