Regulatory Flood Zones Pearland enforces a Flood Damage Prevention Ordinance as mandated by FEMA's National Flood Insurance Program (NFIP). The City Engineer operates as the Floodplain Administrator. City of Pearland participates in FEMA's Community Rating System (CRS), which entitles residents to a premium discount on flood insurance. The City has attained a Class 6 rating. Due to this rating, the residents living in the Special Flood Hazard Area (zone AE) receive a 20% discount on their flood insurance premium and the residents living outside of the hazard area receive a 10% discount. The 100-year floodplain is the land that is predicted to flood during a 100-year storm event, which has a 1% chance of occurrence or annual exceedance probability (AEP) in any given year. The 100-year flood is a standard used by the NFIP for floodplain management and to determine the need for flood insurance. Figure 5.5 shows the FEMA regulatory floodplains within the City and floodway extent, as well as the watersheds.
Historic Floods: Hurricane Harvey In August 2017, a devastating Category 4 hurricane made landfall on Texas and Louisiana. Named Hurricane Harvey, the storm caused catastrophic flooding in the Gulf Coast region, primarily from disastrous rainfall-triggered flooding across the Greater Houston area. Pearland prepared a Hurricane Harvey Damage Assessment Report that reported rainfall from 30 to 49 inches for the City and surrounding area over four days. The storm greatly surpassed historical rainfall from all other historical storms. The rainfall exceeded the 0.2% annual exceedance probability, commonly known as the 500- year storm throughout Harris and Brazoria counties. The report lists 1,080 residences that experienced minor flood damage and 641 that experienced major flood damage. The report also recorded 22 businesses with minor losses and 11 with major losses. The experience from Hurricane Harvey has caused City engineering staff to re-evaluate drainage design criteria and policies. The 2019 Master Drainage Plan Update report includes recommendations for detention related to reducing flooding. Another resilience measure considered after Hurricane Harvey included policies inclined toward burying overhead electric and telecommunication lines. NOAA Atlas 14 In September 2018, the National Oceanographic and Atmospheric Administration (NOAA) released an updated rainfall document called NOAA Atlas 14 Precipitation Frequency Atlas of the United States. This document, prepared by the National Weather Service’s Hydrometeorological Design Studies Center (HDSC), provides precipitation frequency information for the US states and territories. NOAA precipitation frequency estimates serve as the de-facto standard for designing, building, and operating infrastructure to withstand the forces of heavy precipitation and floods. Atlas 14 data changed the rainfall data and associated return periods for a given rainfall depth. For the general Pearland area, the new Atlas 14 data pushed the 100-year rainfall depth from approximately 13.5 inches to approximately 17.0 inches. The City of Pearland updated the drainage criteria and adopted Atlas 14 rainfall for the hydraulic design of drainage infrastructure for both public and private development in the City.
FIGURE 5.5: PEARLAND WATERSHED BOUNDARIES
The Flood Damage Prevention Ordinance adopted by the City prevents the development within the floodway unless it is justified through a drainage study and a Conditional Letter of Amendment (CLOMR) is approved by FEMA prior to construction.
PEARLAND COMPREHENSIVE PLAN 2040
72
Chapter 5
73
Made with FlippingBook. PDF to flipbook with ease