(2) the Connection to River/Watershed Restoration Is Clear

Hi Lyle – You did a good job covering a lot of complex information in your paper. I made some small grammatical and style edits using Track Changes, and included a few comments, too. Usually if you provide an acronym for something (like fluvial geomorphology), you want to use that acronym for all subsequent references in the paper. Definitely check to make sure that everything I changed still reflects what you were trying to communicate, though.

(1)  You definitely gave a strong overview of the topic, and I can tell you did a lot of research. For me (with limited engineering and science background), the text could seem kind of daunting at times, but when I read through it a second time, it made more sense. You might want to do a brief reading with “novice eyes” and see if you can find any way to rephrase or simplify the text so that it is easier for a newbie to understand on first reading.

(2)  The connection to river/watershed restoration is clear.

(3)  I think the grammar, structure, and flow are good. You might want to consider placing Section 3 (case studies) at the end, right before the conclusion, though. It seems like a lot of the text could stand as a good introduction to the case studies.

(4)  Definitely write a conclusion and add references for the final draft. Also be sure to check all your figure citations. You could also add a few sentences to Section 7 that directly address how fluvial geomorphology is related to these biological considerations.

-  Jessica

Fluvial Geomorphology

CE 598 River Restoration

Lyle C. Begay

February 20, 2012

1.  Introduction

Fluvial Geomorphology (FGM) is the study of streams and their interaction with the geologic terrain it hasthey have formed therein. It is a multidisciplinary synthesis of engineering, biology, geology, earth science, hydrology and other science disciplines. It is a developing practice in the area of natural stream channel design stemming from movements to restore river systems. Fluvial GeomorphologyFGM is a holistic science-based view of restoring stream channels by empirical studies such as sediment transport, river discharge, channel size, mapping and others.

2.  History of the Fluvial Geomorphology Field

Fluvial geomorphologyFGM has its roots in the fields of engineering and geoscience that have progressed over the past two centuries. The term fluvial is defined as of, relating to, or inhabiting a river or stream, and geomorphology is the scientific study of landforms and the process that shapes them (en.wikipedia.org). In essence fluvial geomorphologyFGM is the study of landscapes formed from a flowing body of water. Geomorphology is a sub discipline of geoscience and holds a closer relationship to contemporary fluvial geomorphologyFGM. In its essence, geoscience adheres to the inductive scientific method of observation, hypothesis and experimentation. Experimental geoscience is based on a Baconian methodology by of conducting research and producing data for future studies.

In contrast, engineering applies mathematical Newtonian mechanics in order to design structures and systems to promote quality of human life. Since the 18th century engineering design was applied to river systems in order to alleviate flood risk, develop nautical transportation, energy generation and recreational use. The engineering practices provided the framework for early river management, developing laws and standards for water operations. Detention dams, locks and stream channelization were all measures of river control and stabilization but recently have shown costly effects. Such examples include maintenance cost, bed armoring, sediment loading, non-point source pollution and riparian degradation.

Over the past several decades the environmental disruptions of channel stability, water quality and habitats have gathered a growing movement in evolving river restoration and management. A cooperative approach to stream restoration requires understanding the biophysical nature of the river based on its geographic structure and the region’s fluvial process. This incorporated with hydrologic and hydraulic engineering data allows for a more rounded approach to river rehabilitation and non-degrading structures.

Society has become disenchanted with full exploitation of riverine systems and governments such as the US and UK hasve required environmental consideration in their developments. At the same time fluvial methods have expanded and literature has been appropriated especially during the past three decades. Understanding of a river systems involves understanding its historical evolution and definable future involving the implementation of river design. This understanding established the demand for geomorphologists to develop a body of knowledge into rather unknown topic areas such as gravel bed-rivers in extreme environments and continues to do so today. Specialists in fluvial geomorphologyFGM arose in the 1980s, such as Schumm, who describes morphologists as investigators that evaluate models of the landscape by deductive reasoning and measurements of erosion based on extrapolation of empirical relations. During this time Schumm described the components of the fluvial system in three parts and the sediment process which will be discussed further. Leopold and Baker further described the fluvial process in geomorphic terms by publishing field and laboratory research which illustrate water impact on varying landforms, drainage basin patterns and methods for management.

In management discourse policy makers and legislation aligned engineers and geomorphologists during the turn of the century. The two schools of thought formed a relationship around water with differing views; the engineer with intervening institutionalized solutions and the geomorphologist with long-term independent observations. Together the field of FGM has evolved with the bond between the two camps over numerous case projects.

3.  Applications

The following are examples of case studies implemented with environmentally conscious river design as taken from the text Applied Fluvial Geomorphology for River Engineering and Management (Thorne et al, 1997). In simplifying the amount of input from other disciplines (biology, chemistry, law, etc), four classes of geomorphological consultations are represented in the studies.

Direct Intervention in Channel Management

Channel Designs for Flood Protection at Environmentally Sensitive Sites

The first case study was an evaluation of flood relief systems in England and Wales conducted for the UK Ministry of Agriculture. The objectives of the project were to: 1) evaluate performances of implemented systems in terms of discharge capacity, channel stability, construction & maintenance costs and conservation value and 2) develop guidelines for the design of stable flood alleviation/land drainage schemes on mobile-bed channels on the basis of objective 1.

The sites were chosen based on their representation of traditional engineering techniques and evaluated on their riverine environment impacts. The study sites were divided into upper and lower river environments to better compare different systems as can be seen in Ttable 2 (Torne et al, 1997). The sediment transport equation displayed the best forecasting of erosion/deposition in the reaches coupled with the Hey resistance function to evaluate discharge conditions produced comparable measures of environmental impact of each structure. The only stable scheme wereschemes were those incorporating distant flood banks due to the lack of sediment transport regime alteration (erosion/deposition). Two-stage channels are viable due to minimal siltation if applicable;, otherwise, bank-adjacent levees would be the preferred over diversion channels and resectioning.

Indirect/Contingent Intervention: Protecting and Maintaining Channel Capacity

Erosion Protection: Banks

Headward and bank erosion at meander bends along a reach of the River Roding in Loughton, Essex, UK was intensified by channel straightening. Geomorphologists were commissioned to evaluate the use of submerged vanes to alleviate the rate of erosion. The number, size and location of the vanes were calculated to oppose torque forces in the stream and subsequent trials and theory provided for higher degrees of erosion dissipation. Each vane was 3 m long and 1 m high and installed so as to be submerged even during low flow conditions. The developed vane was installed in January 1989 with a fixed position with a main and minor anchoring pile. A survey was carried out after installation and indicated erosion rates were significantly reduced along with bank undercut, over-steepened and mass failures.

Geomorphology of Channels and Water Resource Management

Regulating Reservoirs and Channel Stability

Severn-Trent and Welsh Water Authorities acquired consultation on the maximum levels of release that could be made to the Wye and Severn rivers which would allow their natural stability to be maintained. The basic necessity was to establish release thresholds in regard for bed material entrainment downstream from the outfalls, making the choice of sampling location important. Sites were determined from sinuosity changes implying net erosion and natural instability.

4.  Fluvial Process

In order to understand the geomorphic classifications in stream restoration the fluvial processes must be introduced. The hydrologic cycle pictured below (figure ) illustrates the water scheme in its most general form:. tThe location in which the water cycle occurs, the highest elevations of the land form the boundaries of a watershed, and the crown- shaped area of land draining water to the lower elevations where streams form. Moved by the force of gravity the water infiltrates the soil along its route, transpires into the atmosphere and/or collects into streams and forms a flowing concentrated body of water. This reaction between earth and water is the focus of Fluvial GeomorphologyFGM and is dependent on the driving and resisting forces of a river system in response to erosion and transportation of debris sediment ().

The basic mechanics of the fluvial process involve the balance of the river system’s potential energy. The energy of the flowing water produced in the system (driving force) is balanced by the system’s ability to consume that flow’s energy (resisting force). This balance, or dynamic equilibrium, is a function of the river’s slope, earth materials (sediments), roughness, flow velocity, climate, and channel width and depth. As a fluvial geomorphologist, these factors are accounted for from the site location itself with a good understanding of the river system’s history.

Time factorization itself is a distinction of the river’s life course and can indicate what changes have occurred to the system. It is a fluvial geomorphologist’s task to appropriate when and what type of event occurred to form the current system and its future possibilities. It is worthwhile to note that river system parameters are in a constant flux, continually adapting in response to others; therefore, it is more apt to use the term quasi-equilibrium.

A widely accepted representation of the equilibrium concept is Lane’s Balance relationship which illustrates the changes in a system dependent on four major factors in the formula

(Resisting) QsD50 α QwS (Driving)

where Qs is the bed material, D50 is the median grain size of the bed material, Qw is the dominant discharge, and S is the stream slope. Lane’s balance of resisting vs. driving forces shows that a change in one factor causes a change in another, resulting in degradation, bed scouring/polishing, or aggradation, the deposition of sediment. By this relationship, the system is in equilibrium if the sediment load is transported in and out of the reach.

As mentioned in section 2, Schumm (1977) categorized the fluvial process with regards to the sediment load as a system in three parts (Figure ). The three sediment zones are designated: (1) the upper sediment production zone, (2) the middle sediment transfer zone and (3) the lower sediment deposition zone. The upper sediment production functions as the initial runoff of water from higher elevations with steeper slopes allowing for deeper incisions and cuts into the earth. This zone sees the most erosion activity and develops steeper watercourses such as cascading streams and waterfalls. The middle transfer zone operates as a conveyor belt with softer slopes and is the dominant focus of river restoration. This river reach is the longest of the three zones, and human populations more commonly reside in these areas and see meandering or braided streams. The lower sediment deposition zone may be a lake, delta, or reservoir where the sediment load is dropped off. In river rehabilitation, all three zones must be considered so as not to significantly disrupt the transfer of sediment from zone 1 to zone 3.

Since restoration efforts concentrate on the transfer zone, two fluvial landforms that can be discussed within this region are the floodplains and terraces. Floodplains are flat areas of land that reside along a river and are formed from the deposition of sediments during flood events. Terraces themselves are ancient, abandoned floodplains of a river and are step like in cross section emanating from the river. The river is usually the lowest point as it is the main driver downcutting into the earth and over time it erodes into a new floodplain. Terraces can reveal the events the land has undergone, such as changes in climate, vegetation, tectonic shifts, discharge, and sediment load. More recently human influence such as the installation of dams and high runoff from urbanization has altered the flow regime and produced more terraces.