Hurricane Florence Flooding in Georgetown County: A Qualitative Explanation of the Interactions of Estuary and Tidal River

Abstract

This paper examines data from 18 USGS gauges in the lower Pee Dee Basin in an effort to explain the behavior of the flooding following Hurricane Florence (2018) in Georgetown County, South Carolina. Despite record or near-record flooding in all the tributaries to the Winyah Bay estuary, water levels near the city of Georgetown were well below predicted heights. Floodplain storage in the lower Great Pee Dee, Lynches, and Little Pee Dee River valleys stored over 1.2 million acre-feet of floodwaters, delaying peak stage near Bucksport for five days and reducing peak flow into the Winyah Bay tidal river/estuary system by nearly 50%. An unknown amount of flow from the Winyah Bay tidal river/estuary system flowed through the Atlantic Intracoastal Water Way to Little River rather than through Winyah Bay. The resulting freshwater flow to Winyah Bay only moved the point of tidal stagnation (where upstream tidal flow balances downstream freshwater flow) to near Georgetown. Since the city of Georgetown was near the point of stagnation, water level there was driven by ocean tidal height rather than river flood stage. The lack of discharge data from the tidal rivers in Georgetown County prevents evaluation of the importance of each of these factors and will limit efforts to make quantitative predictions of future flooding in the county.

The Role of a Permeable Sand Column in Modifying Tidal Creek Nutrient Inputs into the Coastal Ocean

“…In addition, high-precipitation events will recharge upland watersheds that will drive substantial freshwater discharges to the coastal ocean. Specifically, the low salinities observed in the primary channel on 17 November 2018 are a probable consequence of Hurricane Florence-induced flooding still occurring as the saturated Pee Dee Basin slowly discharged waters downstream to the lower floodplains (see [41] for analysis of Waccamaw River gauge data).…”

An integrated modelling approach to evaluate the impacts of nature-based solutions of flood mitigation across a small watershed in the southeast United States

“…The state of South Carolina (SC) alone has suffered almost $7 billion in floods and hurricane damages in the last 25 years (SCDNR, 2020). This state was recently overwhelmed by the impacts of five hurricanes in a time span of only seven years, which generated severe riverine floods across cities and towns (Williams et al, 2019). According to the Intergovernmental Panel on Climate Change (IPCC) reports (e.g., IPCC AR6, 2022), there will be an increase in the tropical cyclone rainfall intensities, as well as in the proportion that reaches very intense levels (Category 4 and 5) as a result of climate change (Knutson, 2022;Stone and Cohen, 2017).…”

An integrated modeling approach to evaluate the impacts of nature-based solutions of flood mitigation across a small watershed in the southeast United States

“…The state of South Carolina (SC) alone has suffered almost USD 7 billion in flood and hurricane damages in the last 25 years (SCDNR, 2020). This state was recently overwhelmed by the impacts of five hurricanes in a time span of only 7 years, which generated severe riverine floods across cities and towns (Williams et al, 2019). According to the Intergovernmental Panel on Climate Change (IPCC) reports (e.g., IPCC, 2022), there will be an increase in the tropical cyclone rainfall intensities, as well as in the proportion that reaches very intense levels (Category 4 and 5) as a result of climate change (Knutson, 2022;Stone and Cohen, 2017).…”