45 Hydrogeology (Posters)

Added due to amount of discipline abstracts submitted.

Wednesday, 11 March 2026
9:00 AM - 12:00 PM
RCC, Lower Level Hall

Persistent Sediment and Nutrient Loading in the Urban Fourche Creek Watershed, Little Rock, Arkansas

Paper number: 45-7
Program: Technical Sessions
Time: 9:00 AM – 9:00 AM

Authors

Abstract

Fourche Creek, and several tributary streams within the Fourche Creek Watershed, cover over 70% of the City of Little Rock, Arkansas, and carry non-point pollution, sewage, and debris downstream to the Arkansas River. Urban runoff, primarily collected from impervious surfaces during precipitation events, contributes to nutrient pollution and elevated sediment loads. Stormwater runoff from upstream tributaries discharges into the creeks within the watershed, thereby increasing turbidity. Elevated turbidity values are a primary water quality concern in Arkansas due to the direct relationship with pollutant transport. This study evaluates how turbidity and nutrient loads from urban tributaries relate to downstream water quality in the mainstem of Fourche Creek. 

 

This three-year study focused on three upstream tributaries and three mainstem locations downstream of Fourche Creek. Field parameter measurements included dissolved oxygen, turbidity, pH, temperature, conductivity, and flow velocity. The Arkansas Water Resource Center (AWRC)  analyzed water samples for ammonia-N, nitrogen species, total phosphorus, soluble reactive phosphorus, total dissolved solids (TDS), and total suspended solids (TSS). Additional unfiltered samples were collected quarterly for BOD5, copper, E. coli, and total coliforms. Land-cover maps and watershed boundaries were compared in ArcGIS, with upstream drainage areas delineated using tributary sampling locations as outlet points. These mapped outlet points (Brodie, Rock, and Coleman Creeks) enabled comparison of upstream drainage patterns and their effects on mainstem water quality downstream. 

 

Fourche Creek mainstem sites maintain TSS concentrations comparable to higher-loading tributaries, but are approximately twice those of lower-loading tributaries (e.g., Brodie Creek) with limited recovery between storm events. The urban tributary sites exhibit post-storm spikes, whereas Fourche Creek exhibits persistent sediment loads that do not return to baseline levels after storm events. Total phosphorus concentrations showed a similar pattern with limited dilution between tributary and mainstem sites. Concentrations correlate with TSS, indicating that sediment-associated nutrients are transported downstream within the urban watershed.  These spatial patterns indicate that stormwater is a major contributor to persistent sediment and nutrient loading in the mainstem. The patterns observed in the Fourche Creek Watershed highlight the critical importance of stormwater management in urban tributaries for reducing persistent sediment and nutrient loads.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411801

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