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<br />u02J78 <br /> <br />species. In addition, the Alamar River's riparian habitat and adjacent chaparral habitat <br />serve as invaluable resources for avian species such as the Golden Eagle (Aquila <br />chyrsaetas), Coopers Hawk (Accipiter caaperii), and California Quail (Callipepla <br />calif arnica). Besides avian species, mammals, reptiles, freshwater fish, and amphibians <br />occupy river and riparian habitat. As with bird species, numerous amphibian species such <br />as the arroyo toad (Bufa califarnicus), western spadefoot toad (Spea hammandii), and <br />Pacific tree frog (Hyla regilla) are either threatened or closely monitored in the United <br />States due to declining numbers. If water quality improves, fresh water species, such as <br />the steelhead trout, once again may thrive in the Teeate and Alamar rivers. <br /> <br />The Cost of River Channelization for the Alamar River Corridor <br /> <br />The BorderLink 2000 field research team observed a thriving and diverse riparian <br />habitat corridor in the Alamar River Valley; however, the habitat has been significantly <br />altered by human activities. Unsustainable human activities in and near riparian corridors, <br />have three effects: (1) a decrease in the size of riparian habitat, (2) a decrease in <br />biodiversity over time, and (3) a decrease in green areas in the city and loss of the <br />economic and social benefits that are derived from green areas or river parks. <br />Throughout the Alamar River Corridor, numerous unsustainable human activities that <br />degrade the riparian habitat occur. In this report, however, focus is placed on one <br />particular unsustainable activity: the river channelization and its impact on the Alamar <br />River watershed ecosystem. <br /> <br />The purpose of channelizing a river is to increase channel capacity and flow velocity <br />so that water moves more efficiently downstream and thereby reduces flooding. The <br />BorderLink 2000 research team learned that Mexico's National Water Commission <br />proposes to channelize and line with concrete the Alamar River Corridor for the very <br />reason of quickly removing storm water to reduce flood events. However, recent studies <br />have shown that though the frequency of flooding in the location of the channel is <br />reduced, the severity of flooding when the river is channelized is much greater, <br />particularly downstream (Dallman and Piechota 2000). Channelization also produces <br />many other impacts on water resources and additional environmental problems that are <br />detailed in the following paragraphs. <br /> <br />Channelization serves to remove surface and storm water flows as quickly as possible <br />from the river basin, and to deposit storm water into the ocean. When a river is <br />channelized, riparian vegetation is removed. Since there is no riparian vegetation to slow <br />down surface water flows, ripple pool habitats are lost. Removal of surface and storm <br />water flows significantly reduces the amount of water in ripple pools that recharge <br />groundwater basins (Dallman and Piechota 2000). Concrete channel construction, along <br />with urbanization in the river floodplain, changes the natural river hydrology. These two <br />land use practices result in a significant increase of storm water runoff volume, velocity, <br />and peak volumes in and around the river channels and, thus, creates the potential for <br />erosion and downstream flooding (Dallman and Piechota 2000; San Diego Association of <br />Governments 1997). <br /> <br />31 <br />