North East File Collection - NEFC

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== Analysis of Sediment-Contaminant Distribution in a Straight Tidal River Cross-Section ======

===== Executive Summary and Definitive Answer =====

==== 1.1 Definitive Answer ====

In a contaminated, straight section of a tidal river such as the River Tees, the surface sediment sample least likely to be contaminated will be found in the center of the channel. This location, corresponding to the **thalweg** (the line of greatest depth), is a high-energy environment characterized by the coarsest sediments (e.g., sands and gravels), which possess the lowest affinity for binding chemical contaminants.

==== 1.2 Executive Rationale ====

This conclusion is based on the convergence of three scientific principles: (1) environmental geochemistry, (2) fluvial hydrodynamics, and (3) estuarine sedimentology. Contaminants do not distribute uniformly; they preferentially adsorb to fine-grained, cohesive sediments (silts and clays). The river's flow dynamics then sort these particles by energy. The high-energy mid-channel thalweg acts as a //transport// or //scour zone//, preventing the deposition of these fine, contaminated particles. Conversely, the low-energy channel margins (banks and shoals) act as //depositional sinks//, where contaminated fines accumulate.

==== 1.3 Summary of Evidence ====

This report substantiates this conclusion by synthesizing three key, evidence-based scientific principles:

  - **Geochemical Affinity:** Contaminants, including heavy metals (e.g., Pb, Zn, Cd) and organic pollutants (e.g., PAHs), overwhelmingly bind to fine-grained sediments (silts and clays). This is due to the high specific surface area and electrochemical properties (Cation Exchange Capacity) of these particles, which act as "contaminant sponges".<sup>1</sup>
  - **Hydrodynamic Sorting:** The velocity of flowing water dictates where sediment particles of different sizes are deposited. In a straight channel, flow velocity is highest in the center (thalweg) and lowest at the banks.<sup>4</sup> The high velocity in the thalweg scours away or transports fines, leaving behind coarse, clean sand. The low velocity at the banks allows the fine, contaminated particles to settle and accumulate.<sup>6</sup>
  - **Tidal Dynamics:** The tidal, bi-directional nature of the river introduces a critical "depositional window" known as //slack water//—the period of near-zero velocity when the tide turns.<sup>8</sup> During this period, lateral (cross-channel) flows become dominant, actively transporting suspended, contaminated sediment //out// of the main channel and //onto// the lower-energy banks and shoals, enhancing their contamination.<sup>9</sup>

==== 1.4 Case Study Validation ====

Data from the River Tees estuary, a prime example of a historically contaminated tidal system <sup>10</sup>, confirms this spatial partitioning. Field studies of the Tees differentiate between the sandy, higher-energy zones and the muddy, highly contaminated intertidal zones (banks) and dredged material disposal sites. Monitoring explicitly shows that the "highest mud contents" are found in these designated depositional areas, not in the main transport channels.<sup>13</sup>

===== The Geochemical Imperative: The Affinity of Pollutants for Fine-Grained Sediments =====

==== 2.1 The Fundamental Principle: Adsorption ====

To locate the least contaminated sediment, one must first understand how contaminants are associated with sediment. Pollutants such as heavy metals (Pb, Zn, Cu) and persistent organic pollutants (PAHs) are typically not free-flowing. Instead, they are //adsorbed// onto the surface of sediment particles.<sup>14</sup> This means the accumulation of contaminants is not primarily a function of sediment //volume//, but of sediment //surface properties//. The core question is therefore transformed: the user's query for the "least contaminated" location is, in effect, a query for the location with the "least amount of fine-grained sediment."

==== 2.2 The Role of Particle Size: Fines as Contaminant Sponges ====

It is a well-established principle in environmental geochemistry that fine-grained sediments (defined as particles $<0.063$ mm, or $63$ $\mu$m) sequester significantly higher concentrations of metals and organic pollutants than coarse-grained sands.<sup>1</sup>

This relationship is not linear; it is exponential. Studies show that contaminant loading increases dramatically as particle size decreases. For example, lead (Pb) concentrations have been found to be 10 times higher on the $<0.063$ mm fraction than on larger fractions.<sup>14</sup> Other analyses confirm that the mass loadings of heavy metals like Pb, As, Cd, and Cr are highest in the finest particles (e.g., $<53$ $\mu$m).<sup>16</sup> This is precisely why sediments in contaminated harbors, such as those in the Tees estuary, are characterized as "fine-grained silty material that contains varying concentrations of contaminants".<sup>13</sup>

This principle has a powerful, self-reinforcing effect in highly polluted systems. Research has indicated that the presence of heavy metal pollution can itself //hinder// the natural formation of larger sediment aggregates, leading to an //increase// in the abundance of small particles. This, in turn, "significantly enhancing the distribution of heavy metals in silt and clay aggregates".<sup>18</sup> This creates a feedback loop: pollution creates more of the very substrate (fine silt) that is most effective at transporting and concentrating that same pollution, amplifying its environmental impact.

==== 2.3 The "Why": Mechanisms of Contaminant Sequestration ====

The superior ability of fines to sequester pollutants is driven by two primary mechanisms:

  - **Specific Surface Area (SSA):** The total surface area of a given weight of sediment. A gram of coarse sand has a very low SSA. A gram of clay, composed of microscopic, plate-like mineral structures, has an SSA that can be thousands of times greater.<sup>1</sup> This provides exponentially more "real estate" for contaminants to physically adsorb onto.
  - **Cation Exchange Capacity (CEC):** This is the critical electrochemical mechanism. Clay minerals (e.g., smectites, montmorillonite) are not inert. Due to their atomic structure, they possess a //permanent negative surface charge//.<sup>3</sup> In the water, heavy metals exist as dissolved positive ions (cations), such as $Pb^{2+}$, $Zn^{2+}$, and $Cd^{2+}$. These positive metal ions are electrostatically bound (adsorbed) to the negatively charged clay surfaces, effectively immobilizing them from the water column.<sup>3</sup>
  - **Organic Carbon (OC):** Fine particles of decomposed organic matter, which are hydrodynamically similar to fine silts and clays, also have a high capacity to bind contaminants.<sup>16</sup> Fine sediments and organic matter are often co-deposited.<sup>15</sup> Monitoring of the Tees disposal sites confirms this link, finding the highest Organic Carbon (OC) values (up to 6.09%) in the Inner Tees disposal site <sup>13</sup>, which is also the area with the highest mud content.<sup>13</sup>

==== 2.4 Sediments as Sinks and Sources ====

This strong geochemical affinity makes fine-grained sediments the primary //sink// for river pollution, effectively "scrubbing" the water column but concentrating the contaminants on the bed.<sup>17</sup> In a contaminated river like the Tees, these alluvial deposits become a long-term //secondary source// of pollution.<sup>11</sup> Any disturbance, such as a flood, storm, or dredging, can resuspend these "legacy" fine particles, re-releasing their attached contaminants back into the water.<sup>23</sup> This secondary source dynamic is projected to persist for "many hundreds of years" in the Tees catchment.<sup>11</sup>

===== Hydrodynamic Principles of Sediment Sorting in Fluvial Environments =====

Having established that contaminants are a proxy for fine-grained sediment (fines), the next step is to determine where these fines are most and least likely to be found. This is a question of fluvial hydrodynamics and sediment transport.

==== 3.1 Velocity Distribution in a Straight Channel Cross-Section ====

Water velocity is not uniform across a river channel. It is governed by friction at the channel boundaries (the bed and the banks).

  * At the "wetted perimeter" (the bed and the banks), flow velocity is effectively zero due to frictional drag.<sup>24</sup>
  * Velocity progressively increases with distance from these boundaries.
  * The //maximum flow velocity// in a straight channel is found in the center of the channel, typically just below the water surface.<sup>4</sup>

This creates a distinct cross-sectional energy profile: a //low-energy// environment near the banks and a //high-energy// environment in the center.

==== 3.2 The Thalweg: The River's "High-Energy Core" ====

The //thalweg// is the hydrological term for the line connecting the lowest (deepest) points along the length of a stream bed.<sup>28</sup> In a straight channel, the thalweg is typically located in the center.<sup>29</sup> Because this path is the deepest, it is the furthest from the frictional boundaries of both the bed and the banks. It therefore represents the path of least resistance, and as a result, the thalweg is almost always the line of //fastest// flow in a river.<sup>4</sup> This central, deep thalweg is the "high-energy core" of the river.

==== 3.3 Erosion, Transport, and Deposition: The Hjulström-Sundborg Diagram ====

The Hjulström-Sundborg diagram is a foundational concept in sedimentology that illustrates the relationship between water velocity, particle size, and the processes of erosion (picking a particle up), transport (keeping it in motion), and deposition (letting it settle).<sup>26</sup>

The diagram reveals a critical distinction between coarse and fine particles:

  * **Coarse Particles (Sand/Gravel):** These are heavy and non-cohesive. They require a high velocity to be eroded. As soon as the velocity drops below a certain threshold, they are quickly //deposited//.<sup>6</sup>
  * **Fine Particles (Silt/Clay):** These particles exhibit a "cohesion paradox" that is fundamental to understanding contaminant transport.

  * <WRAP>
    * **Erosion:** Once deposited, fine clay and silt particles are //cohesive//—they stick together due to electrochemical forces.<sup>7</sup> This cohesion means they require a //very high// velocity to be eroded, often higher than the velocity needed to move larger sand grains.<sup>7</sup> This cohesion "locks in" pollution, making contaminated muds on the banks semi-permanent.
    * **Transport & Deposition:** Once these cohesive fines //are// dislodged and in the water column (in suspension), they are tiny and light. They can be transported by //very low// velocities and will only fall out of suspension and be //deposited// in areas of //extremely low// or //near-zero// velocity.<sup>26</sup>
</WRAP>

==== 3.4 Predicting Sediment Facies (The Result of Sorting) ====

Applying these Hjulström-Sundborg principles to the velocity profile of a straight channel (from 3.1) allows for a clear prediction of the sediment distribution:

  * **Mid-Channel (Thalweg):** This is a //persistent high-energy// environment. The high velocities in this zone are //always// above the deposition threshold for fine particles. Therefore, silts and clays //cannot// settle and deposit here; they are kept in suspension and transported downstream.<sup>36</sup> This zone is //transport-dominant// or //net-erosional// for fines, actively scouring them away and leaving behind coarser-grained "lag" deposits of sand or gravel.
  * **Channel Margins (Banks):** These are //persistent low-energy// environments. The low velocity due to bank friction creates an environment that is //below// the transport threshold for fines. This makes the banks a //net-depositional// zone, where fine-grained silts and clays can settle out of the water column and accumulate.

===== The Estuarine Complication: Tidal Dynamics and Depositional Windows =====

The analysis so far applies to a standard unidirectional river. However, the query specifies a //tidal// river, which introduces a critical layer of complexity that //reinforces// this spatial sorting.

==== 4.1 The Defining Feature: Bi-Directional Flow ====

A tidal river is an estuary, defined by its bi-directional flow. The water flows downstream on the ebb tide and upstream on the flood tide.<sup>38</sup> This creates complex, cyclical 3D flow patterns, including helical flows, that are fundamentally different from simple river junctions.<sup>40</sup> The central thalweg, in this environment, becomes a "double-scour" zone: it is subjected to the peak velocity of the //ebb// tide (fluvial flow + tidal ebb) and //also// the peak velocity of the //incoming flood// tide. This makes the mid-channel the most hydrodynamically hostile environment for the permanent deposition of fine sediment.

==== 4.2 The Critical Role of "Slack Water" ====

The most important feature of a tidal system for fine-sediment transport is the "slack water" period. Twice per tidal cycle (at high water and low water), the tide "turns," and the longitudinal (along-channel) velocity drops to //near zero//.<sup>8</sup>

This slack water period is the //only// "depositional window" during which the fine-grained suspended sediment (the contaminant-laden silts and clays) has the opportunity to fall out of suspension.<sup>8</sup> In saline estuarine water, this process is enhanced by //flocculation//, where fine particles clump together, become heavier, and settle more rapidly.<sup>41</sup>

==== 4.3 Lateral Transport: Moving Fines from Channel to Shoal ====

Critically, just as the longitudinal flow ceases, //lateral// (cross-channel) flows become dominant. During slack water, lateral pressure gradients and other forces drive a "lateral redistribution" of sediment.<sup>9</sup>

Studies of channel-shoal systems reveal two typical patterns: shoal-to-channel transport at low water slack and, most importantly, **channel-to-shoal transport at high water slack**.<sup>9</sup> This means that as the contaminated fines begin to settle in the main channel during the high-water slack window, a lateral current actively //pushes// this suspended material //out// of the main channel and //onto// the adjacent banks, shoals, and intertidal flats. This provides a "one-two punch": the tide carries the contamination, slack water allows it to deposit, and lateral flows ensure it deposits preferentially on the //margins//, not in the //center//.

===== Synthesis: Identifying the Cross-Sectional Point of Minimum Contamination =====

==== 5.1 Integrating the Principles ====

The principles of geochemistry, fluvial hydrodynamics, and estuarine dynamics converge to provide a definitive and scientifically robust answer.

  - **Premise 1 (Geochemistry):** Contaminant concentration is a direct proxy for the abundance of fine-grained sediment (silt and clay).
  - **Premise 2 (Fluvial Hydrodynamics):** In any straight channel cross-section, flow energy is highest in the center (thalweg) and lowest at the margins (banks).
  - **Premise 3 (Sedimentology):** High-energy zones (thalweg) scour fines and leave coarse, clean sand. Low-energy zones (banks) accumulate fine, cohesive muds.
  - **Premise 4 (Tidal Dynamics):** The tidal cycle provides a specific mechanism (slack water) and transport pathway (lateral flows) that //actively transfers// the suspended, fine-grained (contaminated) sediment //from// the main channel //onto// the banks and shoals.

==== 5.2 The Predicted Sediment-Contaminant Profile (Bank-to-Bank) ====

This synthesis allows for the prediction of the bank-to-bank contaminant profile:

  * **The Channel Margins (Banks/Shoals):** These are the //low-energy sinks//. They experience low velocity, allowing fines to settle. They are the primary //destination// for contaminated sediment pushed laterally out of the main channel during slack water. Therefore, the banks will be characterized by fine-grained, cohesive, organic-rich, and often anoxic muds and silts.<sup>13</sup> These sediments will have the **highest** contaminant concentrations.
  * **The Mid-Channel (Thalweg):** This is the //high-energy scour zone//. It experiences the "double scour" of peak ebb and flood tides. This persistent high-energy environment //prevents// the permanent deposition of fine-grained sediment and actively //scours// any temporary settlers away, leaving behind a "lag" of coarser, cleaner sediment (sand or gravel).<sup>6</sup> These sediments will have the **lowest** contaminant concentrations.

==== 5.3 Definitive Conclusion ====

The location most likely to yield the //least contaminated// surface sediment sample is in the **center of the channel, along the thalweg (the deepest point)**. This location is hydrodynamically hostile to the deposition and accumulation of the fine-grained, contaminant-bearing particles.

==== 5.4 Comparative Analysis of Cross-Sectional Zones ====

The fundamental differences between the two zones are summarized in Table 1.

**Table 1: Comparative Analysis of Cross-Sectional Zones in a Straight Tidal River**

|**Characteristic**                |**Mid-Channel (Thalweg)**                                                    |**Channel Margins (Banks / Shoals / Intertidal Flats)**                      |
|**Flow Velocity (Peak)**          |**Highest** (Subject to both peak ebb and flood tide velocities) <sup>4</sup>|**Lowest** (High frictional resistance from bank) <sup>24</sup>              |
|**Flow Velocity (Slack Water)**   |**Near-Zero** (Brief window as tide turns) <sup>8</sup>                      |**Near-Zero** (Prolonged window, area of first/last water cover) <sup>9</sup>|
|**Dominant Process**              |**Scour / Transport** (Net-erosional or non-depositional for fines)          |**Deposition / Siltation** (Net-depositional for fines) <sup>9</sup>         |
|**Dominant Sediment Facies**      |**Sand / Gravel** (Coarse-grained lag deposit) <sup>6</sup>                  |**Silt / Clay / Mud** (Fine-grained, cohesive) <sup>13</sup>                 |
|**Specific Surface Area (SSA)**   |**Low** <sup>2</sup>                                                         |**High** <sup>1</sup>                                                        |
|**Cation Exchange Capacity (CEC)**|**Low** <sup>19</sup>                                                        |**High** (Dominated by electro-negatively charged clays) <sup>3</sup>        |
|**Organic Carbon (OC) Content**   |**Low**                                                                      |**High** (Co-deposited with fines) <sup>13</sup>                             |
|**Predicted Contaminant Load**    |**LOWEST**                                                                   |**HIGHEST**                                                                  |

===== Case Study Analysis: Contamination Patterns of the River Tees Estuary ======

==== 6.1 A History of Contamination ====

The River Tees is an ideal case study for this analysis. It is a tidal estuary with a long, well-documented history of severe industrial pollution from mining, chemical processing, and urbanization.<sup>10</sup> As a result, its sediments are known to be contaminated with heavy metals (Zn, Pb, Cu, Cr, Cd, As, Ni) <sup>12</sup> and organic pollutants like polycyclic aromatic hydrocarbons (PAHs).<sup>13</sup> The riverbed is widely recognized as a "dirty" (contaminated) system and a major secondary source of this pollution.<sup>11</sup>

==== 6.2 Evidence from Cross-Channel Surveys ====

The analytical framework presented in this report—that the banks and the mid-channel are fundamentally different environments—is validated by the //sampling design// of major historical surveys of the Tees.

A detailed 1991 survey by Davies et al. was designed to determine total heavy metal concentrations in the estuary's bed sediments. Its methodology explicitly sampled //three// locations at each of 31 sites: one from the **north bank**, one from the **south bank**, and one at **mid‐channel**.<sup>44</sup>

Similarly, a 1981 pilot study by HR Wallingford explicitly differentiated its sampling protocol, collecting **"bed sediments"** (in mid-channel, from a boat using a Van Veen grab sampler) and **"bank deposits"** (from intertidal zones) as two distinct sample sets to be analyzed for heavy metals.<sup>54</sup>

The very design of these foundational studies, which were structured to test for cross-channel variability, confirms the //a priori// scientific understanding that sediment and contaminant characteristics are //not// homogenous across a bank-to-bank line. This lateral variability is the primary factor to account for.

==== 6.3 Sediment Type as a Proxy for Contamination in the Tees ====

While the cited abstracts <sup>52</sup> do not provide the explicit comparative //results// between the banks and the mid-channel from those studies, the principles established in Section 2 (Fines = Contaminants) can be used. By identifying where the fine-grained //muds// and coarse-grained //sands// are located in the Tees, one can confidently predict the contaminant distribution.

  * **Where are the Muds (Contaminated Fines)?**

  * <WRAP>
    * **Intertidal Zones (Banks):** A 2004 study of the Tees estuary focused its core sampling on the "intertidal zone and reclaimed lowlands" <sup>11</sup>—known depositional zones for fine sediment.
    * **Dredged Material Disposal Sites:** These are, by design, //depositional// zones. Monitoring of the Tees Bay disposal sites (e.g., Inner Tees TY160 and Outer Tees TY150) <sup>55</sup> explicitly finds that the **"highest mud contents"** are located //within// these sites.<sup>13</sup> These high-mud areas also correspond to the highest levels of organic carbon.<sup>13</sup>
</WRAP>

  * **Where are the Sands (Cleaner Sediments)?**

  * <WRAP>
    * **Natural Channel Environment:** Monitoring of the same area finds that the sediments //surrounding// the muddy disposal sites are "predominantly unimodal sands" and "muddy sands".<sup>13</sup>
</WRAP>

This creates a clear, observable spatial partitioning on the Tees: The //depositional// zones (intertidal banks, disposal sites) are //muddy// and therefore, by geochemical principle, //highly contaminated//. The //transport// or //scour// zones (the natural channel) are //sandy// and therefore //cleaner//.

This analysis must, however, account for the impact of maintenance dredging.<sup>48</sup> The main navigation channel (mid-channel) of the Tees is artificially over-deepened and requires dredging to remove //silt//.<sup>60</sup> This may appear to contradict the "scour zone" thesis. However, it is an artificial condition that //proves// the principle. The over-deepened channel acts as an artificial "sump" that traps the finest, contaminant-bearing sediment //only// during the brief slack-water window. This material would naturally be scoured or transported to the banks. The dredging process is simply a man-made substitute for this natural scouring. The fact that the dredged material //is// fine-grained, contaminated silt, which is then relocated to the disposal sites (which become the "highest mud content" zones) <sup>13</sup>, confirms that the thalweg is the primary //transport pathway// for fines, not their final //depositional sink//.

===== Conclusion and Implications for Sampling and Management =====

==== 7.1 Final Conclusion ====

The analysis of geochemical principles, sedimentological processes, and estuarine hydrodynamics leads to a high-confidence, definitive conclusion. Based on this synthesis, the location //most likely// to yield the //least contaminated// surface sediment sample on a bank-to-bank cross-section in a straight, tidal river like the Tees is the **mid-channel thalweg**.

This location is a high-energy "scour zone," subjected to the peak velocities of both the ebb and flood tides. This environment hydrodynamically prevents the permanent deposition of the fine-grained silts and clays that transport the vast majority of contaminants. These contaminated fines are instead preferentially deposited in the low-energy zones at the channel margins (the banks and intertidal shoals), which act as the system's primary contaminant sinks.

==== 7.2 Implications for Environmental Sampling ====

This conclusion has critical implications for the design of any environmental survey in such an estuary:

  * **Avoid Single-Point Samples:** A single sample taken from either the bank or the mid-channel cannot be considered representative of the entire river cross-section.<sup>61</sup>
  * **Stratify by Hydrodynamic Zone:** "Contaminant survey designs that account for sedimentation characteristics" are essential.<sup>62</sup> A scientifically valid sampling program //must// stratify its sampling based on the hydrodynamic environment. This means treating the //depositional// (low-energy) muddy facies on the banks and the //transport// (high-energy) sandy facies in the thalweg as distinct geochemical environments to be sampled and analyzed separately.

==== 7.3 Implications for Management (Dredging and Remediation) ====

This analysis provides a predictive framework for managing contaminated sediments in the River Tees and similar estuaries:

  * **Targeted Dredging:** Maintenance dredging of the main channel is, in effect, the targeted removal of the most recently settled, contaminated fine sediments.<sup>60</sup> The disposal of this material, for example at sites TY160 and TY150 <sup>13</sup>, is a //relocation// of this contaminated mud. This creates new, concentrated contaminant hotspots that must be carefully managed.<sup>13</sup>
  * **Targeted Remediation:** The "dirty" sediments on the Tees are not homogenous but are concentrated in specific, predictable depositional zones.<sup>48</sup> The long-term, legacy reservoirs of historical pollution reside in the fine-grained sinks: the **intertidal flats, banks, and muddy shoals**.<sup>11</sup> Remediation strategies should be focused on these specific, high-contamination zones rather than the more dynamic, and naturally cleaner, sandy thalweg.

===== Works cited =====

  - Partitioning of Metal Contaminants between Bulk and Fine-Grained ..., accessed on November 17, 2025, [[https://www.mdpi.com/2075-163X/11/6/603|//https:%%//%%www.mdpi.com/2075-163X/11/6/603//]]
  - accessed on November 17, 2025, [[https://www.researchgate.net/figure/Correlation-between-physical-and-chemical-properties-of-sediment-and-heavy-metals_fig8_383668218#:~:text=Numerous%20studies%20have%20shown%20that,et%20al.%2C%202024)%20.|//https:%%//%%www.researchgate.net/figure/Correlation-between-physical-and-chemical-properties-of-sediment-and-heavy-metals_fig8_383668218#:~:text=Numerous%20studies%20have%20shown%20that,et%20al.%2C%202024)%20.//]]
  - Clay-Based Materials for Heavy Metals Adsorption: Mechanisms, Advancements, and Future Prospects in Environmental Remediation - MDPI, accessed on November 17, 2025, [[https://www.mdpi.com/2073-4352/14/12/1046|//https:%%//%%www.mdpi.com/2073-4352/14/12/1046//]]
  - 18.2: Channel Geometry and Flow Characteristics - Geosciences ..., accessed on November 17, 2025, [[https://geo.libretexts.org/Bookshelves/Geography_(Physical)/The_Physical_Environment_(Ritter)/18%3A_Fluvial_Systems/18.02%3A_Channel_Geometry_and_Flow_Characteristics|//https:%%//%%geo.libretexts.org/Bookshelves/Geography_(Physical)/The_Physical_Environment_(Ritter)/18%3A_Fluvial_Systems/18.02%3A_Channel_Geometry_and_Flow_Characteristics//]]
  - 2B.3 Stream Features and Deposits – Environmental Geology, accessed on November 17, 2025, [[https://minnstate.pressbooks.pub/environmentalgeology/chapter/stream-features/|//https:%%//%%minnstate.pressbooks.pub/environmentalgeology/chapter/stream-features///]]
  - accessed on November 17, 2025, [[https://opentextbc.ca/physicalgeology2ed/chapter/13-3-stream-erosion-and-deposition/#:~:text=As%20the%20flow%20velocity%20increases,be%20transported%20in%20the%20stream.|//https:%%//%%opentextbc.ca/physicalgeology2ed/chapter/13-3-stream-erosion-and-deposition/#:~:text=As%20the%20flow%20velocity%20increases,be%20transported%20in%20the%20stream.//]]
  - The Hjulström Curve: Simple Explanation with Diagram - The Geo Room, accessed on November 17, 2025, [[https://thegeoroom.co.zw/hydrology/the-hjulstrom-curve-of-river-erosion-transportation-and-deposition/|//https:%%//%%thegeoroom.co.zw/hydrology/the-hjulstrom-curve-of-river-erosion-transportation-and-deposition///]]
  - Transport and Deposition of Suspended Sediments on Estuarine Tidal Flats: ABSTRACT | AAPG Bulletin | GeoScienceWorld, accessed on November 17, 2025, [[https://pubs.geoscienceworld.org/aapg/aapgbull/article-abstract/56/3/601/556433/Transport-and-Deposition-of-Suspended-Sediments-on|//https:%%//%%pubs.geoscienceworld.org/aapg/aapgbull/article-abstract/56/3/601/556433/Transport-and-Deposition-of-Suspended-Sediments-on//]]
  - Delft University of Technology Study of Sediment Transport in a ..., accessed on November 17, 2025, [[https://pure.tudelft.nl/ws/files/89122758/2020JC016334.pdf|//https:%%//%%pure.tudelft.nl/ws/files/89122758/2020JC016334.pdf//]]
  - The River Tees Case Study, accessed on November 17, 2025, [[https://teamgeographygcse.weebly.com/the-river-tees-case-study.html|//https:%%//%%teamgeographygcse.weebly.com/the-river-tees-case-study.html//]]
  - Tidal sedimentation in the Tees estuary during the 20th century: Radionuclide and magnetic evidence of pollution and sedimentary response | Request PDF - ResearchGate, accessed on November 17, 2025, [[https://www.researchgate.net/publication/222052965_Tidal_sedimentation_in_the_Tees_estuary_during_the_20th_century_Radionuclide_and_magnetic_evidence_of_pollution_and_sedimentary_response|//https:%%//%%www.researchgate.net/publication/222052965_Tidal_sedimentation_in_the_Tees_estuary_during_the_20th_century_Radionuclide_and_magnetic_evidence_of_pollution_and_sedimentary_response//]]
  - Tees management catchment: baseline length of rivers and estuaries polluted by abandoned metal mines - GOV.UK, accessed on November 17, 2025, [[https://www.gov.uk/government/publications/abandoned-metal-mines-in-england-baseline-length-of-rivers-and-estuaries-polluted-by-harmful-metals/tees-management-catchment-baseline-length-of-rivers-and-estuaries-polluted-by-abandoned-metal-mines|//https:%%//%%www.gov.uk/government/publications/abandoned-metal-mines-in-england-baseline-length-of-rivers-and-estuaries-polluted-by-harmful-metals/tees-management-catchment-baseline-length-of-rivers-and-estuaries-polluted-by-abandoned-metal-mines//]]
  - Dredged Material Disposal Site Monitoring Around the Coast of England: Results of Sampling (2023-2024) Tees (Inner and Outer) - GOV.UK, accessed on November 17, 2025, [[https://assets.publishing.service.gov.uk/media/667d290f4ae39c5e45fe4d08/C6794_Dredge_Disposal_Monitoring_Annual_Report_2023-2024_Tees_v2.0.pdf|//https:%%//%%assets.publishing.service.gov.uk/media/667d290f4ae39c5e45fe4d08/C6794_Dredge_Disposal_Monitoring_Annual_Report_2023-2024_Tees_v2.0.pdf//]]
  - Heavy metal content in relation to particle size and organic content of surficial sediments in Miami River and transport potential | Request PDF - ResearchGate, accessed on November 17, 2025, [[https://www.researchgate.net/publication/303691959_Heavy_metal_content_in_relation_to_particle_size_and_organic_content_of_surficial_sediments_in_Miami_River_and_transport_potential|//https:%%//%%www.researchgate.net/publication/303691959_Heavy_metal_content_in_relation_to_particle_size_and_organic_content_of_surficial_sediments_in_Miami_River_and_transport_potential//]]
  - Heavy Metal Accumulation in Sediments of Small Retention Reservoirs—Ecological Risk and the Impact of Humic Substances Distribution - MDPI, accessed on November 17, 2025, [[https://www.mdpi.com/2079-9276/11/12/113|//https:%%//%%www.mdpi.com/2079-9276/11/12/113//]]
  - Distribution Characteristics of Heavy Metals in Different Particle Size Fractions of Chinese Paddy Soil Aggregates - MDPI, accessed on November 17, 2025, [[https://www.mdpi.com/2227-9717/11/7/1873|//https:%%//%%www.mdpi.com/2227-9717/11/7/1873//]]
  - The Processing and Beneficial Use of Fine-Grained Dredged Material - Rutgers CAIT, accessed on November 17, 2025, [[https://cait.rutgers.edu/wp-content/uploads/2018/05/193-ru2763_1.pdf|//https:%%//%%cait.rutgers.edu/wp-content/uploads/2018/05/193-ru2763_1.pdf//]]
  - A review on adsorption characteristics and influencing mechanism of heavy metals in farmland soil - PMC - NIH, accessed on November 17, 2025, [[https://pmc.ncbi.nlm.nih.gov/articles/PMC9890661/|//https:%%//%%pmc.ncbi.nlm.nih.gov/articles/PMC9890661///]]
  - Competitive Adsorption Processes at Clay Mineral Surfaces: A Coupled Experimental and Modeling Approach | ACS Earth and Space Chemistry, accessed on November 17, 2025, [[https://pubs.acs.org/doi/10.1021/acsearthspacechem.1c00323|//https:%%//%%pubs.acs.org/doi/10.1021/acsearthspacechem.1c00323//]]
  - Comprehensive Review on the Adsorption Properties of Clay Minerals for Enhanced Removal of Toxic Dyes and Heavy Metals - Journal of Water and Environmental Nanotechnology, accessed on November 17, 2025, [[https://www.jwent.net/article_721169_3a2cab98534d29f1af78ced22ddc9bba.pdf|//https:%%//%%www.jwent.net/article_721169_3a2cab98534d29f1af78ced22ddc9bba.pdf//]]
  - Adsorption of reovirus to clay minerals: effects of cation-exchange capacity, cation saturation, and surface area - PubMed, accessed on November 17, 2025, [[https://pubmed.ncbi.nlm.nih.gov/6639022/|//https:%%//%%pubmed.ncbi.nlm.nih.gov/6639022///]]
  - Siltation - Wikipedia, accessed on November 17, 2025, [[https://en.wikipedia.org/wiki/Siltation|//https:%%//%%en.wikipedia.org/wiki/Siltation//]]
  - Adsorption and migration of heavy metals between sediments and overlying water in the Xinhe River in central China - IWA Publishing, accessed on November 17, 2025, [[https://iwaponline.com/wst/article/84/5/1257/83382/Adsorption-and-migration-of-heavy-metals-between|//https:%%//%%iwaponline.com/wst/article/84/5/1257/83382/Adsorption-and-migration-of-heavy-metals-between//]]
  - Section 1: Open Channel Flow - Texas Department of Transportation, accessed on November 17, 2025, [[https://www.txdot.gov/manuals/des/hyd/chapter-6--hydraulic-principles/section-1--open-channel-flow.html|//https:%%//%%www.txdot.gov/manuals/des/hyd/chapter-6--hydraulic-principles/section-1--open-channel-flow.html//]]
  - BASIC HYDRAULIC PRINCIPLES OF OPEN-CHANNEL FLOW - USGS Publications Warehouse, accessed on November 17, 2025, [[https://pubs.usgs.gov/of/1988/0707/report.pdf|//https:%%//%%pubs.usgs.gov/of/1988/0707/report.pdf//]]
  - 13.3 Stream Erosion and Deposition – Physical Geology, accessed on November 17, 2025, [[https://opentextbc.ca/geology/chapter/13-3-stream-erosion-and-deposition/|//https:%%//%%opentextbc.ca/geology/chapter/13-3-stream-erosion-and-deposition///]]
  - Velocity Distribution - Open Channel Flow, accessed on November 17, 2025, [[https://study.madeeasy.in/ce/open-channel-flow/velocity-distribution/|//https:%%//%%study.madeeasy.in/ce/open-channel-flow/velocity-distribution///]]
  - Thalweg - Wikipedia, accessed on November 17, 2025, [[https://en.wikipedia.org/wiki/Thalweg|//https:%%//%%en.wikipedia.org/wiki/Thalweg//]]
  - River Cha ne1 Pattern, accessed on November 17, 2025, [[https://pubs.usgs.gov/pp/0282b/report.pdf|//https:%%//%%pubs.usgs.gov/pp/0282b/report.pdf//]]
  - Fluvial Process: Waterways and Hydrology - AustinTexas.gov, accessed on November 17, 2025, [[https://www.austintexas.gov/sites/default/files/files/Water/CER/fluvial%20process%20january%202023.pdf|//https:%%//%%www.austintexas.gov/sites/default/files/files/Water/CER/fluvial%20process%20january%202023.pdf//]]
  - accessed on November 17, 2025, [[https://nanofase.eu/show/hjulstr%C3%B6m-curve_1737#:~:text=Hjulstr%C3%B6m%20curve%20describes%20the%20relationships,particle%20size%20and%20water%20velocity.|//https:%%//%%nanofase.eu/show/hjulstr%C3%B6m-curve_1737#:~:text=Hjulstr%C3%B6m%20curve%20describes%20the%20relationships,particle%20size%20and%20water%20velocity.//]]
  - Understanding the Hjulstrom curve - Cool Geography, accessed on November 17, 2025, [[https://www.coolgeography.co.uk/A-level/AQA/Year%2012/Rivers_Floods/Long%20profile/Hjulstrom.htm|//https:%%//%%www.coolgeography.co.uk/A-level/AQA/Year%2012/Rivers_Floods/Long%20profile/Hjulstrom.htm//]]
  - 13.3 Stream Erosion and Deposition – Physical Geology – 2nd Edition - BC Open Textbooks, accessed on November 17, 2025, [[https://opentextbc.ca/physicalgeology2ed/chapter/13-3-stream-erosion-and-deposition/|//https:%%//%%opentextbc.ca/physicalgeology2ed/chapter/13-3-stream-erosion-and-deposition///]]
  - Hjulstrom Curve explained - YouTube, accessed on November 17, 2025, [[https://www.youtube.com/watch?v=HW6FBj17vlk|//https:%%//%%www.youtube.com/watch?v=HW6FBj17vlk//]]
  - Fluid flow: Shields and Hjulström diagrams - Geological Digressions, accessed on November 17, 2025, [[https://www.geological-digressions.com/fluid-flow-shields-and-hjulstrom-diagrams/|//https:%%//%%www.geological-digressions.com/fluid-flow-shields-and-hjulstrom-diagrams///]]
  - Help with understanding a Graph about Sedimentation and Erosion depending on flow speed : r/geology - Reddit, accessed on November 17, 2025, [[https://www.reddit.com/r/geology/comments/kdx5b7/help_with_understanding_a_graph_about/|//https:%%//%%www.reddit.com/r/geology/comments/kdx5b7/help_with_understanding_a_graph_about///]]
  - SEDIMENT TRANSPORT and DEPOSITION - J.Amorocho Hydraulics Laboratory - UC Davis, accessed on November 17, 2025, [[https://jahl.engr.ucdavis.edu/research/sediment-transport-and-deposition/|//https:%%//%%jahl.engr.ucdavis.edu/research/sediment-transport-and-deposition///]]
  - Flow, Sediment, and Morpho-Dynamics of River Confluence in Tidal and Non-Tidal Environments - MDPI, accessed on November 17, 2025, [[https://www.mdpi.com/2077-1312/8/8/591|//https:%%//%%www.mdpi.com/2077-1312/8/8/591//]]
  - The Role of River Discharge and Geometric Structure on Diurnal Tidal Dynamics, Alabama, USA - NIH, accessed on November 17, 2025, [[https://pmc.ncbi.nlm.nih.gov/articles/PMC9287036/|//https:%%//%%pmc.ncbi.nlm.nih.gov/articles/PMC9287036///]]
  - (PDF) Three-Dimensional Hydrodynamics and Morpho-dynamics at a Tidal River Junction, accessed on November 17, 2025, [[https://www.researchgate.net/publication/375772784_Three-Dimensional_Hydrodynamics_and_Morpho-dynamics_at_a_Tidal_River_Junction|//https:%%//%%www.researchgate.net/publication/375772784_Three-Dimensional_Hydrodynamics_and_Morpho-dynamics_at_a_Tidal_River_Junction//]]
  - Flow and Sediment Transport on a Tidal Salt Marsh Surface, accessed on November 17, 2025, [[https://tidalmarshmonitoring.net/pdf/Christiansen%20et%20al%202000.pdf|//https:%%//%%tidalmarshmonitoring.net/pdf/Christiansen%20et%20al%202000.pdf//]]
  - LECTURE 3 - Fluvial Geomorphology - Ecological Engineering, accessed on November 17, 2025, [[https://storm.fsv.cvut.cz/data/files/p%C5%99edm%C4%9Bty/SRPP/Lecture%203%20-%20CTU143SRPP(1).pdf|//https:%%//%%storm.fsv.cvut.cz/data/files/p%C5%99edm%C4%9Bty/SRPP/Lecture%203%20-%20CTU143SRPP(1).pdf//]]
  - Sediments | US EPA, accessed on November 17, 2025, [[https://www.epa.gov/caddis/sediments|//https:%%//%%www.epa.gov/caddis/sediments//]]
  - Heavy metals in river tees estuary sediments - Semantic Scholar, accessed on November 17, 2025, [[https://www.semanticscholar.org/paper/73d4fd12376e8f4a86c6b3d2992d755bb3bf8fa0|//https:%%//%%www.semanticscholar.org/paper/73d4fd12376e8f4a86c6b3d2992d755bb3bf8fa0//]]
  - Spatial distribution and risk assessment of heavy metal(loid)s in sediments and marine organisms in the Yellow River estuary and its adjacent areas, China - Frontiers, accessed on November 17, 2025, [[https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1560640/full|//https:%%//%%www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1560640/full//]]
  - Spatial Distribution, Risk Index, and Correlation of Heavy Metals in the Chuhe River (Yangtze Tributary): Preliminary Research Analysis of Surface Water and Sediment Contamination - MDPI, accessed on November 17, 2025, [[https://www.mdpi.com/2076-3417/14/2/904|//https:%%//%%www.mdpi.com/2076-3417/14/2/904//]]
  - TEES Water Body - Defra data services platform, accessed on November 17, 2025, [[https://environment.data.gov.uk/catchment-planning/WaterBody/GB510302509900|//https:%%//%%environment.data.gov.uk/catchment-planning/WaterBody/GB510302509900//]]
  - MLA/2025/00263 – Report of the Investigation of the Sediment Quality Data of L/2015/00427/7 - North East File Collection - NEFC, accessed on November 17, 2025, [[https://northeastfc.uk/NEMRG/250806NEMRG-MLA_2025_00263-SedimentQualityInvestigation.pdf|//https:%%//%%northeastfc.uk/NEMRG/250806NEMRG-MLA_2025_00263-SedimentQualityInvestigation.pdf//]]
  - Spatial and seasonal variations in depth profile of metals in some sediments from Red Sea Islands and the effect of grain size | Request PDF - ResearchGate, accessed on November 17, 2025, [[https://www.researchgate.net/publication/239793162_Spatial_and_seasonal_variations_in_depth_profile_of_metals_in_some_sediments_from_Red_Sea_Islands_and_the_effect_of_grain_size|//https:%%//%%www.researchgate.net/publication/239793162_Spatial_and_seasonal_variations_in_depth_profile_of_metals_in_some_sediments_from_Red_Sea_Islands_and_the_effect_of_grain_size//]]
  - Seasonal variation of heavy metals concentration in sediments of the rivers and estuaries of Sundarban mangrove forest | Request PDF - ResearchGate, accessed on November 17, 2025, [[https://www.researchgate.net/publication/286547962_Seasonal_variation_of_heavy_metals_concentration_in_sediments_of_the_rivers_and_estuaries_of_Sundarban_mangrove_forest|//https:%%//%%www.researchgate.net/publication/286547962_Seasonal_variation_of_heavy_metals_concentration_in_sediments_of_the_rivers_and_estuaries_of_Sundarban_mangrove_forest//]]
  - (PDF) Changes in the Sediment Trace Metal Contamination after the Commissioning of a Municipal Wastewater Treatment Plant in the Souss Estuary (South Morocco) - ResearchGate, accessed on November 17, 2025, [[https://www.researchgate.net/publication/5463711_Changes_in_the_Sediment_Trace_Metal_Contamination_after_the_Commissioning_of_a_Municipal_Wastewater_Treatment_Plant_in_the_Souss_Estuary_South_Morocco|//https:%%//%%www.researchgate.net/publication/5463711_Changes_in_the_Sediment_Trace_Metal_Contamination_after_the_Commissioning_of_a_Municipal_Wastewater_Treatment_Plant_in_the_Souss_Estuary_South_Morocco//]]
  - heavy-metals-in-river-tees-estuary-sediments - Ask this paper | Bohrium, accessed on November 17, 2025, [[https://www.bohrium.com/paper-details/heavy-metals-in-river-tees-estuary-sediments/811884714280353794-3176|//https:%%//%%www.bohrium.com/paper-details/heavy-metals-in-river-tees-estuary-sediments/811884714280353794-3176//]]
  - Survey of heavy metals in the sediments of the Swartkops River Estuary, Port Elizabeth South Africa - ResearchGate, accessed on November 17, 2025, [[https://www.researchgate.net/publication/268338426_Survey_of_heavy_metals_in_the_sediments_of_the_Swartkops_River_Estuary_Port_Elizabeth_South_Africa|//https:%%//%%www.researchgate.net/publication/268338426_Survey_of_heavy_metals_in_the_sediments_of_the_Swartkops_River_Estuary_Port_Elizabeth_South_Africa//]]
  - Estuarine transmission of heavy metal pollutants - pilot study of the ..., accessed on November 17, 2025, [[https://eprints.hrwallingford.com/108/1/SR64.pdf|//https:%%//%%eprints.hrwallingford.com/108/1/SR64.pdf//]]
  - Dredged Material Disposal Site Monitoring Around the Coast of England: Results of Sampling (2009) - GOV.UK, accessed on November 17, 2025, [[https://assets.publishing.service.gov.uk/media/5a8062f540f0b62302693333/SLAB5_Report_2009-10.pdf|//https:%%//%%assets.publishing.service.gov.uk/media/5a8062f540f0b62302693333/SLAB5_Report_2009-10.pdf//]]
  - Dredged Material Disposal Site Monitoring Around the Coast of England: Results of Sampling (2012) - GOV.UK, accessed on November 17, 2025, [[https://assets.publishing.service.gov.uk/media/5a80400eed915d74e622d59c/SLAB5_Report_2012-13.pdf|//https:%%//%%assets.publishing.service.gov.uk/media/5a80400eed915d74e622d59c/SLAB5_Report_2012-13.pdf//]]
  - REPORT Tees Maintenance Dredge Protocol (MDP) Baseline, accessed on November 17, 2025, [[https://northeastfc.uk/RiverTees/Planning/MLA_2025_00263/Additional%20Documents/Tees%20MDP%20Baseline%20Document%20May%2025.pdf|//https:%%//%%northeastfc.uk/RiverTees/Planning/MLA_2025_00263/Additional%20Documents/Tees%20MDP%20Baseline%20Document%20May%2025.pdf//]]
  - Dredged Material Disposal Site Monitoring Around the Coast of England: Results of Sampling (2014) - GOV.UK, accessed on November 17, 2025, [[https://assets.publishing.service.gov.uk/media/5a80d55740f0b62302695c20/SLAB5_Report_2014-15.pdf|//https:%%//%%assets.publishing.service.gov.uk/media/5a80d55740f0b62302695c20/SLAB5_Report_2014-15.pdf//]]
  - Tees and Hartlepool Maintenance Dredge Disposal Licence - GOV.UK, accessed on November 17, 2025, [[https://www.gov.uk/government/publications/tees-and-hartlepool-maintenance-dredge-disposal-licence|//https:%%//%%www.gov.uk/government/publications/tees-and-hartlepool-maintenance-dredge-disposal-licence//]]
  - Tees Maintenance Dredging Annual Review 2019 - North East File Collection - NEFC, accessed on November 17, 2025, [[https://www.northeastfc.uk/Teesworks/Planning/MLA_2024_00166/Additional%20Documents/PC1115-RHD-ZZ-XX-RP-Z-0001%20Tees%20MDP%20baseline%20update%202019%20(2).pdf|//https:%%//%%www.northeastfc.uk/Teesworks/Planning/MLA_2024_00166/Additional%20Documents/PC1115-RHD-ZZ-XX-RP-Z-0001%20Tees%20MDP%20baseline%20update%202019%20(2).pdf//]]
  - Identifying sediment sources in the tees catchment - Durham E-Theses, accessed on November 17, 2025, [[http://etheses.dur.ac.uk/3684/1/3684_1245.pdf|//http:%%//%%etheses.dur.ac.uk/3684/1/3684_1245.pdf//]]
  - A survey of benthic sediment contaminants in reaches of the Columbia River Estuary based on channel sedimentation characteristics - USGS Publications Warehouse, accessed on November 17, 2025, [[https://pubs.usgs.gov/publication/70101339|//https:%%//%%pubs.usgs.gov/publication/70101339//]]