Distribution and Behavior of Fine Sediment in the Severn Estuary and Inner Bristol Channel, U.K.

Abstract

During the 10 yr, 1970–80 a variety of field measurements using some new techniques have allowed the distribution of muddy sediment in the Severn Estuary and Inner Bristol Channel to be defined. Based on these measurements, a behavioral model has been adopted comprising mobile and stationary suspensions, and settled mud. The regional distribution of mobile suspensions shows a suspended solids front located along the main channel axis with the more turbid water on the southern, English, side. At maximum current velocities on spring tides, vertical suspended sediment profiles are homogeneous. As velocity decreases, a stepped structure develops due to settling, which is then remixed on the next accelerating semidiurnal tidal phase. Over the lunar timescale these steps become more stable, eventually settling to the bed. The steps are unrelated to salinity, temperature, grain-size, or mineralogy. On neap tides, layered, acoustically detectable stationary suspensions, which occasionally consolidate to form settled mud, develop from the mobile suspensions. An idealized "three-zone" model has been devised characterizing the structures developed in the mobile suspensions.Key words: Severn Estuary, vertical profiling, siltmeter, densimeter, suspended solids, fronts, stratification

Estuarine Turbidity Maxima and Variations of Aggregate Parameters in the Cam-Nam Trieu Estuary, North Vietnam, in Early Wet Season

“…Because of the strong influences of marine water, tide and river discharge, the occurrence of ETMs is complex and difficult to predict [1,2]. They are trapping a lot of suspended matter and encompass a huge range of SPM concentrations with maximum values from less than 100 mg L −1 like in the Kennebec Estuary, USA [3,4] to >200 g L −1 like in the Severn Estuary, UK [5]. The settling of SPM in an ETM has been well documented in the Gironde Estuary [6][7][8], the Hudson estuary [9][10][11], the Columbia River estuary [12], the Seine estuary [13], the upper Chesapeake Bay [14,15], and the Humber Estuary [16], amongst others.…”

Numerical simulation of fluid mud layer in estuaries and coastal areas

“…Quantitative measurements offluidmudjn_J;heS_exenuvere ! !_Q_1;_available but the behaviour of the model fits well with the description of fluid mud in the Severn given by Kirby and Parker [2]. It is planned to further develop the model to include the effect of waves.…”

“…The ADI method was used, with staggered grid for the derivative in respect to space and Leap-frog scheme for time. The corresponding difference equations are given in previous paper (Chung and.Roberts [2]. Therefore the model shows to be applicable in practice, and that the numerical simulation can be fully carried out on PC.…”

Cohesive Sediment Flocculation and the Application to Settling Flux Modelling

“…Of particular importance, a quantitative understanding of the dynamics of the vertical structure of cohesive sediments in suspensions is essential for an accurate estuarine sedimentation model (Kirby, 1986;van Leussen, 1991). This requires an understanding of the physical processes related to the entrainment, advection and deposition of muddy sediments.…”