Abstract
The elevated supply of fine-grained sediment to a river system negatively impacts the water quality and ecosystem health. Therefore, quantification of the relative contribution from different sources to in-stream sediment is of major interest to target sediment mitigation best management practices (BMPs). The objective of this study was to determine the relative contribution from different sources of suspended sediment in an urbanized watershed (31 km2) located in the eastern part of Alabama, USA. Estimates of relative contributions from individual source types were assessed for two different particle size fractions, 63–212 μm (fine sand) and <63 μm (silt and clay). Results of this study indicate that the construction sites were the dominant source of suspended sediment in this watershed. The average annual subwatershed-level surface runoff determined using the Soil and Water Assessment Tool (SWAT) model varied from 2.3 to 11,980 mm ha−1 year−1. Areas that generate high surface runoff have the potential to contribute disproportionately high amounts of sediment to streams and therefore should be targeted for BMPs. The results of this study show that it is important to consider spatial and temporal variability in suspended sediment sources in order to develop and target sediment control management strategies. The sources of suspended sediment and sediment deposited on the stream bed might not necessarily be the same. Therefore, sampling both suspended sediment and stream bed sediment will improve our knowledge of watershed-level sediment transport processes.
Highlights
Nonpoint source (NPS) pollution has been identified as the leading cause of surface water impairment in the USA, and sediment has been considered to be the most common NPS pollutant [1,2]. moderate quantities of in-stream sediment are beneficial for aquatic habitats, provide nutrient enrichment to floodplain ecosystems, and ensure sediment replenishment to coastal zones [3,4], elevated supplies of suspended sediment from terrestrial and aquatic sources to surface waters as a result of anthropogenic activities negatively impact aquatic ecosystems [5,6]
The number of fingerprinting properties that successfully discriminated between the construction sites and stream banks at all sites for the two particle sizes ranged from 9 to 21 (Tables 4 and 5)
The results of the stepwise discriminant function analysis (DFA) on the fingerprinting properties that passed the Mann Whitney test for 63–212 μm and
Summary
Nonpoint source (NPS) pollution has been identified as the leading cause of surface water impairment in the USA, and sediment has been considered to be the most common NPS pollutant [1,2]. Moderate quantities of in-stream sediment are beneficial for aquatic habitats, provide nutrient enrichment to floodplain ecosystems, and ensure sediment replenishment to coastal zones [3,4], elevated supplies of suspended sediment from terrestrial and aquatic sources to surface waters as a result of anthropogenic activities negatively impact aquatic ecosystems [5,6]. Excessive sediment delivery to surface waters can increase turbidity, deliver sediment-bound nutrients to streams and lakes, and result in sedimentation of the river bed [7]. In the state of Alabama (AL), USA, for approximately 34% of the impaired streams and rivers, sedimentation has been considered as the potential cause of impairment [8].
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