Longitudinal patterns in sediment type and quality during daily flow regimes and following natural hazards in an urban estuary: a Hurricane Harvey retrospective

Abstract

Understanding the transport of sediments in urban estuaries and their effects on water quality and microorganisms is a convergent challenge that has yet to be addressed especially as a result of natural hazards that affect the hydrodynamics of estuarine systems. This study provides a holistic view of the longitudinal nature and character of sediment in an urban estuary, the Galveston Bay Estuary System (GBES), under daily and extreme flow regimes and presents the results of water and sediment sampling after Hurricane Harvey. The sediment sampling quantified total suspended sediment (TSS) concentrations, metal concentrations, and the diversity of microbial communities. The results revealed the impact of the substantial sediment loads that were transported into the GBES in terms of sediment grain type, the spatial distribution of trace metals, and the diversity of microbial communities. A measurable shift in the percentage of silt relative to historical norms was noted in the GBES after Hurricane Harvey. Not only did sediment metal data confirms this shift and its ensuing impact on metal concentrations; microbial data provided ample evidence of the effect of leaks and spills from wastewater treatment plants, superfund sites, and industrial runoff on microbial diversity. The research demonstrates the importance of understanding longitudinal sediment transport and deposition in estuarine systems under daily flow regimes but more critically, following natural hazard events to ensure sustainability and resilience of systems such as the GBES that encounter numerous acute and chronic stresses.

Supporting nformation (SI)

ESM 1

Bed Sediment Sampling. Deposited Soil sampling. Quality Assurance for Sediment Sampling. List of WQM stations with their studied parameters (Table S1), Criteria for trace metals in dry soils (mg/kg) (Table S2), PCLs for trace metals in wet sediment samples (mg/kg) (Table S3), Maximum and most recent historical trace metal concentrations in sampled sediment sites (Table S4), Total depth, sediment total organic carbon (TOC), and field water quality parameters measured at the bed layer of waterbodies (Table S5). Muddy waters in Rivers of Brown, Galveston Bay, and Gulf Mexico in the aftermath of Hurricane Harvey. (A) On August 31, 2017, 6 days after Hurricane Harvey’s landfall. Photo captured by Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. (B) through (D) are Sentinel 2, Level-2A: Bottom of atmosphere reflectance, true color photos from 9/1/17, 10/1/17, and 10/11/17, respectively (Figure S1), Spatial distribution of A) soil type, and B) erosion potential in the Greater Houston metropolitan (Figure S2), TSS concentrations plotted against the flow rates at the time of sampling for four of the major bayous in the GHMA (Figure S3), Grain type distribution in sediment samples collected from the tidal segments of the HSC-GB system post Hurricane Harvey for different stations (Figure S4), Deposited soil along Buffalo Bayou in Buffalo Bayou Park (29.764, -95.384) close to BB5 (see Figure 1 in the manuscript) Photos taken on 09/17/2017 (Figure S5), Location of deposited soil sampling stations and tidal sampling location relative to nearby Superfund sites (Figure S6). (DOCX 9579 kb)