In the 1980s, USAID (US Agency for International Development) funded an environmental assessment of dams on the Gambia River, which determined that construction of the Balingho anti-salinity barrage would result in adverse unmitigative environmental and social consequences. Attempts by host country politicians, USAID and UNDP (United Nations Development Programme) to discredit this process made it necessary to take the matter to the Natural Resource Defense Council. A case study of the events surrounding these dams and their potential construction illustrates the ‘big dam’ paradigm and its potential harm to people, their livelihoods and the environment in Sub-Saharan Africa.

The River Roding near Abridge, Essex was monitored during 1979-82 to assess the short-term ecological effects of recent and contemporary river engineering works on a small, rural watercourse. Increased environmental awareness by Thames Water Authority river engineers and scientists resulted in implementation of an ecologically-sensitive flood alleviation scheme which provided an ideal opportunity for a pioneer case study. Sampling procedure was designed to describe aquatic and riparian habitats, flora and fauna along the watercourse. An extensive, 27 Jan survey revealed that the middle Roding was a typical, highly modified clay river, with limited conservation value. Intensive, continuous monitoring was confined to a 5km stretch; with reference to annual variations recorded in a control site, ecological change produced by three phases of engineering works between 1974 and 1980, each involving two-stage flood relief channels, are described. The magnitude of disturbance to the original habitat determined ecological impact. Retention of in-channel and waterside habitats ensured normal vegetation growth the following Spring, benefitting dragonflies and fish; furthermore, the subsequent development of a richer 'channel-margin' flora produced an increase in waterbird territories. By contrast, excavation below water level severely retarded waterside vegetation recovery, while construction of a trapezoidal, concrete-lined channel produced an impoverished environment which greatly reduced habitat diversity. Silting, plus greater aquatic plant growth in response to increased light levels caused by berm excavation, reduced channel discharge capacity, accentuated by dense Phalaris arundinacea stands on unmanaged berms subject to regular summer inundation. An hydraulically efficient two-stage profile which improves riverine wildlife potential could be produced by retention of the original dry-weather channel; excavation, from one bark, of shallow flood berms which remain dry throughout the summer; tree-planting to counter the effects of increased light; sowing low-profile grasses; and regular grazing or cutting of berm vegetation.

published_or_final_version / abstract / toc / Geography / Doctoral / Doctor of Philosophy

No description available.

This study investigates changes to channel morphology along Chilliwack River in southwest British Columbia, and relates these changes to the transport of bed material. The channel was mapped using a stereoplotter from a sequence of historical aerial photography between 1952 and 1991. Maps for selected years were overlaid, then analyzed with a GIS. Erosion and deposition volumes of bed material were determined by multiplying measured planimetric changes by the varying depth of bed material along the river. A sediment budget framework was used to estimate bed material transport rates from these net changes in stored sediment volumes. The transport rate of bed material for Chilliwack River is estimated as 55,000±10,000 m3/yr for the period 1983 to 1991. Instability along lower channel reaches has increased over the 40 year period of study due to an increase in both the magnitude and frequency of large floods. As a consequence, channel width, bank erosion rates and the volume of sediment transported past Vedder Crossing became increasingly large. Between 1952 and 1975, Chilliwack River was in a transient state of equilibrium as the channel continued to recover from a sequence of large floods in previous decades. Large floods in 1975 and 1980 caused significant bank erosion along lower reaches, which increased the amount of sediment available for transport. Extreme floods in 1989 and 1990 caused further erosion, and in fact, were large enough to alter the pre-flood channel regime. However, in the absence of further large floods, the channel should recover from these events in 10 to 20 years. Significant morphologic change on Chilliwack River occurs roughly once every 5 years, when peak flows exceed 500 m3/s. These floods are sufficient to erode channel banks, where the dominant supply of mobile bed material is stored. Aggradation occurs in the short term as more sediment is introduced to the active channel zone than can be removed by subsequent smaller flows. However, as flows as small as 250 m3/s (which occur several times per year, on average) are capable of mobilizing bed material, there is net degradation over the longer term. As the length between survey dates used in this study averaged 10 years, some information on bed material transport between dates is lost. Nonetheless, this study has demonstrated that considerable information on historic channel change can be obtained form aerial photographs.

The purpose of this practicum is to explore the Cheakamus River from its beginning at Outlier Peak to its arrival at Howe Sound. I explored it in terms of its history, both geological and cultural; its uses both past and present; and in terms of ‘place’. I determined there had not been development in the area, due to geological instability and its unique location. I explored the place, its unique characteristics and its rarity. My exploration was through photography, writing and drawing. I explored the culture of the Cheakamus by looking at its role in the mythology of the First Nations People of the area. By looking at the notions of retreat, renewal, meditation and contemplation, I explored the stimmung, genus loci and zen of this river system. Finally, I made connections between the river and the land, highlighting the uniqueness of place.

No description available.

Farming practices within the upper Selwyn plains have significantly expanded, and are becoming more dependent on groundwater as a reliable source of irrigation. This expansion has resulted in the rapid development of the groundwater resource and water levels in many wells have reached record low levels. Groundwater resources can be found within at least three aquifers within the glacial gravel deposits of the upper Selwyn plains. Aquifer 1 occurs between approximately 0-30 m, aquifer 2 between 40-85 m and aquifer 3 greater than 100 m below the surface. Aquifers 1 and 2 occur within close proximity to the Selwyn River and its tributaries. Aquifer 1 is unconfined, aquifer 2 semi-confined and aquifer 3 semi-confined to confined. Significant leakage of groundwater occurs between the different aquifers. Recharge sources to the aquifers include rainfall infiltration and river seepage. Water levels and groundwater chemistry suggest that the Selwyn River provides the dominant source of recharge to aquifers 1 and 2 in areas immediately surrounding the river and to the south of the current course of the river between Greendale and Dunsandel.

No description available.

No description available.