Variations of suspended sediment yields in nested urban catchments
Abstract
Near real-time turbidity and discharge data were collected continuously for four years at five stream gages over three nested watershed scales (DR2, DR5, 1-2 km2 ; DR3, DR4, 5-6 km2; DRKR, 14 km2) in the highly impervious Dead Run watershed, located in Baltimore County, MD. The design of this study represented a unique opportunity to compare sediment yields across spatial and temporal scales in an urbanized watershed.
Monthly suspended sediment yields varied by over two orders of magnitude across all stations. are on tributaries to the mainstem of Dead Run, located only about 500 m apart and about 500 m upstream of their confluence, yet only two of the top five monthly suspended yields at each of these stations is also among the top five at the other station. Average annual yield is higher at the headwater station with older development (DR5; 78.2 t/km2/yr) than at the station with more recent development (DR2; 47.0 t/km2/yr). Average annual yields increase with watershed size from the headwater stations to the mid-watershed stations (DR4; 87.0 t/km2/yr, DR3; 60.4 t/km2/yr). Yields at the downstream station (DRKR; 81.7 t/km2/yr) are slightly larger than the yield calculated from the sum of both mid-watershed stations (DR3+DR4; 74.6 t/km2/yr), which together represent about 80% of the upstream drainage area. Several additional patterns highlighting spatial heterogeneity of the system were observed. The ratios of sediment yields between the headwater DR5 and DR2 stations increased steadily over time while the runoff ratios remained almost constant. Yields at the mid-watershed DR4 station were consistently higher than yields at the paired DR3 station, despite similar runoff totals. However, regardless of significant fluctuation in upstream yields, yields at the mouth of the watershed showed minimal variation. This observation is consistent with the possibility that internal storage and remobilization tend to modulate downstream yields even with significant upstream variation. Despite significant internal variability, the overall range of sediment yields at each site were consistent with values tabulated for other mid-Atlantic urban watersheds. Comparison with global values indicates that sediment yields from Dead Run are in the same general range as the 25% quartile of urban sediment yields.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H41Q2374K
- Keywords:
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- 0493 Urban systems;
- BIOGEOSCIENCESDE: 1847 Modeling;
- HYDROLOGYDE: 1878 Water/energy interactions;
- HYDROLOGYDE: 1880 Water management;
- HYDROLOGY