Sediment transport in a 2.6
km
2 steep, undisturbed headwater rainforest Sungai Pangsun catchment in the Ulu Langat Forest Reserve in Selangor, Peninsular Malaysia was measured during a 12-month ...period. The rainfall and runoff recorded during the study period from July 1997 to June 1998 were 2052 and 866
mm, respectively. This was an unusually dry water year, affected by the El Nino/Southern Oscillation phenomenon; rainfall was about 30% below the long-term mean of 2514
mm. Suspended sediment yield computed from in situ readings taken at 15
min intervals was 21.8
t. Bedload yield, measured with a hand-held Helley-Smith sampler and by deposition in a stilling pool at the catchment outlet was 4.6 and 11.4
t, respectively. Due to difficulties in sampling bedload during storm discharge with the Helley-Smith sampler, biweekly measurements of deposition in the pool were considered the more reliable. Two major storm events, in October 1997 and May 1998, contributed 45% of the total bedload yield indicating the importance of peak flows on bedload transport in the catchment. Episodic bedload transport was also attributed to the influence of coarse woody debris, particularly in places where sediments were stored behind debris accumulations along the stream channel—about 60% of the 16
m
3 of woody debris mapped in a 300
m reach upstream of the gauging site was mobilized during the October event. During the 12-month study period, suspended and bedload sediment comprised 66 and 34%, respectively, of the total sediment transport. The higher ratio for suspended load was largely due to the dry study period. It is envisaged that bedload would contribute a higher proportion of sediment during normal hydrologic years.
This paper synthesizes information on the spatial and temporal dynamics of wood in small streams in the Pacific Northwest region of North America. The literature on this topic is somewhat confused ...due to a lack of an accepted definition of what constitutes “small” streams and what is the relative size of woody debris contained within the channel. This paper presents a matrix that defines woody debris relative to channel size and then discusses the components of a wood budget. Headwater streams are in close proximity to wood sources and, in steeplands, are often tightly constrained by steep hillslopes. Special consideration is given to ecosystem characteristics and to management practices that affect the wood dynamics in this context. Knowledge gaps and uncertainties that can be used to guide future research are identified. Very little is currently known about the role of mass wasting in wood recruitment and storage relative to other processes, such as bank erosion and mortality, in larger streams. Further, very little work has addressed the relative importance of different wood depletion processes, especially those associated with wood transport. The effect of other ecosystem variables on wood dynamics locally across a watershed (from valley bottom to mountaintop) and regionally across the landscape (from maritime to continental climates) is not addressed. Finally, the scientific community has only begun to deal with the effects of management practices on wood quantity, structure, and movement in small streams.
Wood debris (WD) transport processes accompanied with the formation and failure of WD dams were studied in a small fourth-order basin with steep bedrock low-order channels in Hokkaido, Japan. The ...basin experienced three floods between 1992 and 2006. WD dams are wood debris accumulations that completely block channels and retain large volumes of sediment upstream. They are common in forested mountain streams with small bankfull widths, and affect transport of both WD and sediment in mountainous watersheds. Mapping and dimensional measurement of the WD dams in the study basin have revealed that many dams are distributed throughout first- and second-order channels (<10 m in width) and that these dams trap a relatively small amount of sediment, whereas fewer dams occur in third- and fourth-order channels (15-45 m in width). A dam in the fourth-order channel in the study basin was found to retain a huge amount of sediment along a 500-m reach of riverbed upstream. Half of all the WD dams in low-order (first- and second-order) channels form at the place of WD recruitment by streamside landsliding, and the other half form after WD is transported in channels by debris flows. Repeated mapping of WD dams in the low-order channels before and after flooding in 2003 and 2006 revealed that 90% erosion of dams occurs during large floods and 40% erosion occurs during middle-scale floods. Three stages of WD transport processes were identified : the first stage includes processes from WD recruitment through WD dam formation in low-order channels ; the second stage comprises failure of WD dams in low-order channels, WD transport downstream, and WD deposition in high-order channels (dam formation in some cases) ; and the third stage includes failure of stable WD dams in high-order channels, WD release, and downcutting of elevated riverbeds. In the study basin, sediment storage behind WD dams was found to account for 40-70% of all sediment stored in low-order channels and 50-60% of that in high-order channels. Therefore, formation and failure of WD dams that function as major sediment reservoirs significantly affect sediment transport in mountainous terrain
The interaction between today’s polluted urban atmosphere and materials leads to the formation of sulphated black crusts containing industrial fly-ash. While many historical documents report the ...existence of polluted air in towns prior to the modern industrial era, such descriptions have not so far been substantiated by any scientific analysis of samples of older interactions. A new approach is proposed, based on the study of crusts found in Arles and Bologna, which formed in the periods 1180–1636, and 1530–1887, respectively. They are grey, mostly calcitic, and contain wood debris and micrometric siliceous or alumino-silicated spherules. The same tracers were also encountered in the smoke from experimental wood fires. This approach confirms the presence of air polluted by wood combustion in the towns of Southern France and Northern Italy during the Medieval up to pre-industrial age. Such information, near to the source, completes the evidence provided in written documents, as well as the data obtainable, farther from the sources, using core samples of glaciers, lakes and marine sediments.
Freshwater mussel assemblages in the Flint River Basin (FRB) of southwestern Georgia are among the most diverse in the southeastern Coastal Plain of North America. Historically, 29 species, including ...7 endemics, occurred in the FRB. A drought during the summer of 2000 caused record low flows and many perennial streams dried or became intermittent. Predrought surveys conducted in 1999 allowed an assessment of the impact of the drought on mussel assemblages. During 2001, 21 stream reaches that had abundant or diverse mussel assemblages in 1999 were resurveyed. Study sites were classified as flowing or non-flowing during the drought based on data from stream gauging stations or visual observation of study reaches. Mussels were classified by conservation status, either stable, special concern, or federally endangered. Greater than 90% of the mussels observed in the lower FRB were species with stable conservation status. Special-concern species represented 5 to 6% and endangered species represented 1% of mussel abundance. Sites that ceased flowing during the drought had significant declines in the abundance of stable species and in taxa richness. Endangered species also showed evidence of a decline in non-flowing sites. Sites that maintained flow had increases in stable species and no change in special concern, endangered species, or species richness through the drought. Sites that showed declines in mussel abundance had a significantly lower frequency of wood debris than other sites. Field observations suggested that shallow depressions beneath wood debris may act as refuges for freshwater mussels during stream drying. Greatest declines in mussel abundance usually occurred in the mid-reaches of the major tributaries of the lower Flint River. These reaches depend on the Upper Floridan aquifer, which is heavily used for irrigation, to maintain base flows. Declines in mussel populations appear to be associated with unusual climatic conditions and increasing demand on the area streams and the regional aquifer system for irrigation water supply.
Freshwater mussel assemblages in the Flint River Basin (FRB) of southwestern Georgia are among the most diverse in the southeastern Coastal Plain of North America. Historically, 29 species, including ...7 endemics, occurred in the FRB. A drought during the summer of 2000 caused record low flows and many perennial streams dried or became intermittent. Predrought surveys conducted in 1999 allowed an assessment of the impact of the drought on mussel assemblages. During 2001, 21 stream reaches that had abundant or diverse mussel assemblages in 1999 were resurveyed. Study sites were classified as flowing or non-flowing during the drought based on data from stream gauging stations or visual observation of study reaches. Mussels were classified by conservation status, either stable, special concern, or federally endangered. Greater than 90% of the mussels observed in the lower FRB were species with stable conservation status. Special-concern species represented 5 to 6% and endangered species represented 1% of mussel abundance. Sites that ceased flowing during the drought had significant declines in the abundance of stable species and in taxa richness. Endangered species also showed evidence of a decline in non-flowing sites. Sites that maintained flow had increases in stable species and no change in special concern, endangered species, or species richness through the drought. Sites that showed declines in mussel abundance had a significantly lower frequency of wood debris than other sites. Field observations suggested that shallow depressions beneath wood debris may act as refuges for freshwater mussels during stream drying. Greatest declines in mussel abundance usually occurred in the mid-reaches of the major tributaries of the lower Flint River. These reaches depend on the Upper Floridan aquifer, which is heavily used for irrigation, to maintain base flows. Declines in mussel populations appear to be associated with unusual climatic conditions and increasing demand on the area streams and the regional aquifer system for irrigation water supply.
The cutting of trees for site construction and development had become a predominant factor in Ghana. Besides, the practice of cutting and leaving tree roots in the soil had become an impediment, such ...as harbouring wild reptiles like snakes, iguanas and an infestation of termites. These factors endanger individual lives, especially living in such environments. This study focused on repurposing wood detritus as a functional concept in the interior design. The study sought to analyse neem tree roots and their properties for a decorative piece in interior design. As a studio-based inquiry, the study employed the aesthetico-action model with a narrative method on the techniques and procedures for executing the studio work. It was evident from the studio practice that wood detritus such as neem tree root serves as an embodiment of inherent qualities, ideas and artistic expressions based on its roots' natural forms. Artists should focus on tree roots (stumps) left in the soil and on the environment as a material for art production in the interior space design.
