# Forestry Best Management Practices Relationships with Aquatic and Riparian Fauna: A Review
## 3 Results and Discussion
### BMP Effectiveness  
The literature also indicates that BMPs developed for forest roads, skid trails, stream crossings, and streamside management zones (SMZs) have greater potential to reduce sedimentation and also benefit riparian and aquatic species. Of all silvicultural activities, roads and skid trails have the largest potential to contribute excess sediment [48; 49]; poorly designed and maintained roads and skid trails have been shown to increase soil erosion, regardless of harvest intensity [44; 45; 47]. Forestry BMPs for road and skid trails have consistently been shown to be effective for limiting sediment inputs [49; 50; 51; 52; 53; 54; 55; 56; 57; 58]. Effective sediment control from forest roads involves appropriate design and template selection, minimization of road grade (particularly at stream crossing approaches), use of water control and retention structures, and achieving adequate cover or surfacing for travel surfaces [48].  
Road and skid trail stream crossing approaches surfaced with grass, slash, or gravel are examples of highly effective BMPs that can slow or prevent sediment inputs to aquatic environments [59; 60; 61; 62; 63]. Changes in macroinvertebrate functional feeding groups and assemblages in streams associated with harvest treatments and forest road construction and maintenance activities implemented with BMPs are often indistinguishable from natural variations [64].  
Forestry BMPs also include a number of water control and diversion methods to prevent sedimentation, particularly on roads and skid trails. Water turnouts and water bars can reduce stream water sedimentation by diverting water flow away from streams and into riparian filter strips, thereby reducing runoff velocity and allowing sediment to be deposited on land [11; 58; 61]. While stream crossings with a greater area will have greater erosion potential, water turnout and wing ditch BMPs will decrease the stream crossing approach length, thereby reducing the amount of potential sediment inputs [62]. In the Virginia Piedmont, [PERSON] et al. [61] found that appropriate spacing of water control structures can reduce sediment loss. A continuous berm along the edge of a forest road in the Coastal Plain of North Carolina reduced sediment loss by an average of 99% [65]. Maximizing water bar surface roughness and increasing water bar frequency are also effective measures in reducing sediment delivery to streams [66]. [PERSON] et al. [58] found that ditch BMPs can be used to effectively reduce sediment contributions from road ditches.  
Streamside management zones and riparian buffers have consistently been shown to reduce sedimentation in aquatic environments [53; 54; 67]. On the Appalachian Plateau region of eastern Kentucky, [PERSON] et al. [68] found that in watersheds where BMPs (including riparian buffers) were applied, water yield, sediment flux, and nutrient inputs were similar to non-harvested watershed sites. [PERSON] et al. [53] found that SMZs trapped approximately 89-97% of watershed erosion before reaching streams. In the Georgia Piedmont, [PERSON] and [PERSON] [69] found that SMZs were effective for trapping sediment from overland flow, averaging 81% efficiency [11]. Although SMZs applied to harvest units in the highly erodible bluff hills of the Gulf Coastal Plain in Mississippi were not effective in reducing overland flow, they reduced total suspended solid (TSS) concentrations due to the preservation of riparian characteristics [70]. Variability in results among studies may be attributed to differences in topography, geology/soils, and hydrology, but the results of this particular study were attributed to the formation of gullies that breached the SMZ [70]. BMP efficacy is dependent on site-specific characteristics (i.e., site history, disturbance or logging history, topography, slope, climate, etc.); studies consistently have shown the capacity for forestry BMPs to effectively prevent excessive sedimentation of aquatic environments [1; 2; 3; 4; 10; 11; 17].