Roads are a widespread and increasing feature of most landscapes. We reviewed the scientific liter- ature on the ecological effects of roads and found support for the general conclusion that they are associated with negative effects on biotic integrity in both terrestrial and aquatic ecosystems. Roads of all kinds have seven general effects: mortality from road construction, mortality from collision with vehicles, modification of animal behavior, alteration of the physical environment, alteration of the chemical environment, spread of exotics, and increased use of areas by humans. Road construction kills sessile and slow-moving organisms, injures organisms adjacent to a road, and alters physical conditions beneath a road. Vehicle collisions affect the demography of many species, both vertebrates and invertebrates; mitigation measures to reduce roadkill have been only partly successful. Roads alter animal behavior by causing changes in home ranges, move- ment, reproductive success, escape response, and physiological state. Roads change soil density, temperature, soil water content, light levels, dust, surface waters, patterns of runoff, and sedimentation, as well as adding heavy metals (especially lead), salts, organic molecules, ozone, and nutrients to roadside environments. Roads promote the dispersal of exotic species by altering habitats, stressing native species, and providing movement corridors. Roads also promote increased hunting, fishing, passive harassment of animals, and landscape modifications. Not all species and ecosystems are equally affected by roads, but overall the pres- ence of roads is highly correlated with changes in species composition, population sizes, and hydrologic and geomorphic processes that shape aquatic and riparian systems. More experimental research is needed to com- plement post-hoc correlative studies. Our review underscores the importance to conservation of avoiding con- struction of new roads in roadless or sparsely roaded areas and of removal or restoration of existing roads to benefit both terrestrial and aquatic biota.

/pdf/review-of-ecological-effects-of-roads-on-terrestrial-and-4pqj0rsd84.pdf

Review of ecological effects of roads on terrestrial and aquatic communities.

A review of the braided-river depositional environment

A method is presented which enables the computation of the bed-load transport as the product of the saltation height, the particle velocity and the bed-load concentration. The equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity. Experiments with gravel particles (transported as bed load) are selected to calibrate the mathematical model using the lift coefficient as a free parameter. The model is used to compute the saltation heights and lengths for a range of flow conditions. The computational results are used to determine simple relationships for the saltation characteristics. Measured transport rates of the bed load are used to compute the sediment concentration in the bed-load layer. A simple expression specifying the bed-load concentration as a function of the flow and sediment conditions is proposed. A verification analysis using about 600 (alternative) data shows that about 77% of the predicted bed-load-transport rates are within 0.5 and 2 times the observed values.

Sediment transport; Part I, Bed load transport

A method is presented which enables the computation of the suspended load as the depth-integration of the product of the local concentration and flow velocity. The method is based on the computation of the reference concentration from the bed-load transport. Measured concentration profiles have been used for calibration. New relationships are proposed to represent the size gradation of the bed material and the damping of the turbulence by the sediment particles. A verification analysis using about 800 data shows that about 76% of the predicted values are within 0.5 and 2 times the measured values.

Sediment Transport, Part II: Suspended Load Transport

Brahmaputra River : Channel processes and sedimentation

https://rosap.ntl.bts.gov/view/dot/1024/dot_1024_DS1.pdf

Evaluating Scour at Bridges

/pdf/summary-of-alluvial-channel-data-from-flume-experiments-1956-3j5yoji50z.pdf

Summary of alluvial channel data from flume experiments, 1956-61

Paper presents initial results of flume study of alluvial channels; detailed classification of regimes of flow, forms of bed roughness, and basic concepts pertaining to resistance to flow; description of experimental equipment and procedure; criteria for washout of dunes and for decrease of resistance to flow; hysteresis observed at changes in dune bed.

/pdf/resistance-to-flow-in-alluvial-channels-4j9lds4kz2.pdf

Resistance to Flow in Alluvial Channels

https://rosap.ntl.bts.gov/view/dot/25666/dot_25666_DS1.pdf

Stream stability at highway structures.

Field studies and laboratory experiments in large recirculating flume have established that resistance to flow and sediment transport in alluvial channels are related to form of bed roughness; forms of roughness can be divided into lower and upper regimes of flow on basis of their shape, resistance to flow, and sediment transport; possible relationship that may prove useful in predicting configuration of bed is introduced.

/pdf/forms-of-bed-roughness-in-alluvial-channels-2khv6ff7ll.pdf

Everett V. Richardson

Papers

Evaluating Scour at Bridges

Summary of alluvial channel data from flume experiments, 1956-61

Resistance to Flow in Alluvial Channels

Stream stability at highway structures.

Forms of Bed Roughness in Alluvial Channels