Riparian-Buffer Loss and Pesticide Incidence in Freshwater Matrices of Ikpoba River (Nigeria): Policy Recommendations for the Protection of Tropical River Basins

The unregulated use of watersheds for agriculture negatively impacts the quality of river basins. In particular, the reduced quality of surface-waters, have been attributed to absence or poorly-decided riparian-buffer specifications in environmental laws. To demonstrate suitable buffer-width for protection of surface water, sediment and benthic fish populations, five riparian areas with different vegetation richness and buffer-width were selected within an organochlorine pesticide (OCP)-impacted watershed using the Normalized Differential Vegetation Index (NDVI) and multiple buffer analysis respectively. Mean OCP levels in surface water, sediment and fish sampled at each riparian stations showed site-specific differences with markedly higher levels of α-BHC, β-BHC, δ-BHC, p,p′-DDD and total pesticide residues at stations with least riparian cover. The principal component analysis further revealed more OCPs associating with sediment and fish from stations having smaller buffer-width and sparse riparian vegetation. Stations with wider buffer-width of at least 120 m provided greater protection to adjacent surface water and benthic fish populations. While this study recommends riparian buffer-widths for a typical tropical environment, further research which assesses other contaminant types in aquatic matrices adjacent to different riparian environments would be valuable and informative for regulatory guidance and strategic protection of ecosystem services.

Dimensioning of riparian buffer zones in agricultural catchments at national level

<p>Intensive agricultural production interferes with natural cycles of nutrients (mostly nitrogen and phosphorus) and may lead to water quality degradation due to excessive nutrient loadings. To mitigate this effect at the landscape level establishment of buffering vegetated strips is an efficient measure.</p><p>Recommending optimal widths for riparian buffer zones to reduce the agricultural runoff is still a challenging task, in particular when considering the spatial variability of the landscape. Empirical-based approaches include assessment of terrain, soil types, land use and vegetation, and are often realised in computationally expensive hydrological simulation. However, trade-offs have to be made between spatial resolution and areal extent. Another elegant empirical-based approach are nomographs, where via triangulation of a specific slope length, terrain slope and soil type recommended buffer width can be easily calculated. Mander and Kuusemets (1998) already developed such a nomograph for Estonian catchments in 1998, yet, a computational use case has not been explored.</p><p>We implemented the nomograph as a GIS algorithm in Python/QGIS to retrieve the recommended buffer width at national level. We synthesized a specific slope length via a weighted average of flow length, local flow accumulation and LS factor, and then use the specific slope length, slope derived from 5 m spatial resolution DEM and soil texture classes as inputs for the algorithm. We applied this algorithm and calculated recommendable buffer strip widths for the whole of country of Estonia, over an area of approx. 43,000 km<sup>2</sup>. We evaluated the uncertainty of the results as well the algorithm’s sensitivity to input weights.</p><p>The developed algorithm is applicable in any region with relevant adjustments to local soil types. The result directly informs policy making by being able to more specifically decide and explain variations of buffer zone widths along water bodies.</p>

Methods to Detect Edge Effected Reductions in Fire Frequency in Simulated Forest Landscapes

Reductions in fire frequency (RFF) are known to occur in the area adjacent to the rigid-boundary of simulated forest landscapes. Few studies, however, have removed those edge effected regions (EERs), and many others may, thus, have misinterpreted their simulated forest conditions within those unidentified edges. We developed three methods to detect and remove EERs with RFF and applied them to fire frequency maps of 2900 × 2900 grids developed using between 1000 and 1200 fire-year maps. The three methods employed different approaches: scanning, agglomeration, and division, along with the consensus of two and three of those methods. The detected EERs with RFF ranged in mean width from 5.9 to 17.3 km, and occupied 4.9 to 21.3% of the simulated landscapes. Those values are lower than the 40 km buffer width, which occupied 47.5% of the simulated landscape, used in a previous study in this area that based buffer width on length of the largest fire. The maximum width of the EER covaried with wind predominance, indicating it is not possible to prescribe a standard buffer width for all simulation studies. The three edge detection methods differ in their optimality, with the best results provided by a consensus of the three methods. We suggest that future landscape forest simulation studies should, to ensure their results near the rigid boundary are not misrepresentative, simulate an appropriately enlarged study area and then employ edge detection methods to remove the EERs with RFF.

Safety Evaluation of Cross-Sectional Elements of Freeway Managed Lanes

This paper investigated the safety implications of managed-lane cross-sectional elements. The objective of the Federal Highway Administration project was to investigate the relationship between crashes and buffer-separated managed lane dimensions. The results from several previous research studies have demonstrated that reductions in freeway lane width or shoulder width are associated with more crashes. This research found that a narrower managed-lane envelope width (i.e., left shoulder, managed-lane, and buffer width combined) is also associated with more freeway crashes for crashes of all severity levels including fatal and injury. Wider envelopes are associated a reduction in total freeway crashes, of all severities, of 2.8% in Texas, and 2.0% in California, for each additional foot of envelope width. In California, wider envelopes are associated with a reduction of 4.4% in managed-lane-related crashes resulting in fatalities and injuries at all severity levels, for each additional foot of envelope width. The analysis was conducted on nonweaving managed-lane segments that included a single managed-lane separated from the general-purpose lanes with a flush buffer area. The dataset included crashes on 128.0 miles of freeway in California (all 128.0 miles with flush buffers) and 60.4 miles of freeway in Texas (41.7 miles with pylon buffers and 18.7 miles with flush buffers). The California sites included freeways with three or four general-purpose lanes, and the Texas freeways had three to five general-purpose lanes.

Generalizacija linija i AutoCAD Map

The paper offers the results of original research made on the application of AutoCADMap in line generalisation. The differences and similarities have been found out between theDouglas-Peucker method and the method of line simplification that is incorporated inAutoCAD Map. There have been also the inaccuracies found out in AutoCAD Map manualrelating to the issues of buffer width and tolerance, and the line width before and aftersimplification. The paper gives recommendations about pseudo nodes dissolving. It has beennoticed that AutoCAD Map simplification method is not independent of the order of points.The application of the method is illustrated by an example of coastal line of Istria.

Operating Speed on a Buffer-Separated Managed Lane

Managed lanes typically are on or adjacent to freeways and are actively operated and managed to preserve operational performance—such as more optimal travel speeds—over comparable general-purpose traffic lanes. A study was conducted to evaluate speeds on existing buffer-separated managed lanes to identify variables that influence operating speed. Speed data from more than 130 unique sites in Los Angeles, California; Orange County, California; and Dallas, Texas, were used. All analyses showed that the managed lane volume and the speed in the general-purpose lanes were related to the speed in the managed lane (statistically significant). The Dallas analysis, which used speeds averaged by 1-min increments, showed that the factor with the most influence on uncongested managed lane speed was the managed lane’s geometry. The relationship between uncongested managed lane speed and the managed lane envelope (sum of left shoulder width, managed lane width, and buffer width) was found to be statistically significant. For each additional foot over a 16-ft envelope width, managed lane speed increased by approximately 3.2 mph. In contrast, the California analysis, which used speeds averaged by 1-h increments, showed that the variable having the most influence was the volume in the managed lane. The researchers theorized that the lack of a relationship between managed lane speed and geometry in California is related to those speeds being an average 1-h speed rather than the 1-min speeds available in Texas.

Effect of Geometric Factors on Lateral Position of Vehicles in Freeway Buffer-Separated Managed Lanes

Chapter 3 in the 2004 AASHTO high-occupancy-vehicle guidelines includes a prioritized trade-off table of various design options for high-occupancy-vehicle lanes (now known as managed lanes). The design trade-offs include the reduction of lane, shoulder, or buffer width. The key measure thought to be affected by lane, shoulder, and buffer width is lateral position. The presented study identified the relationship between operations and cross-section width, including the type of buffer design separating the managed lanes from the general-purpose lanes. This research study collected lateral position data on existing managed lane facilities with a range of geometric elements within both tangent and horizontal curves and identified potential relationships between the geometric design element values and the measure of effectiveness. The field studies included data collected at 28 sites with fixed video cameras and along 161 centerline miles with an instrumented vehicle that recorded data for the vehicle immediately in front of the instrumented vehicle. The study found that managed-lane drivers shifted away from the pylons placed in the buffer. Horizontal alignment (tangent or curve) and the direction of the horizontal curve (left or right) influenced lateral position. Left shoulder, lane, and buffer width affected lateral position. Modifying a 6.5-ft shoulder to a minimum shoulder (i.e., 1.5 ft) will result in drivers moving to the right about 0.5 ft; however, if an 18.5-ft shoulder is reduced by 5 ft, the impact in operations is negligible (drivers would shift only about 0.11 ft toward the right).