24 Regions and land mosaics
vegetation protecting the stream are interconnected into a complete dendritic
network (Wetzel 2001, Kalff 2002, Binford and Karty2006). In the more wide-
spread agricultural landscapes, tiny intermittent channels and small first-order
streams may have their strips of covering vegetation entirely removed to create
large crop fields requiring large tractors. Considerable wildlife habitat is lost.
Perhaps more importantly, the loss of tiny vegetation strips results in exten-
sive stormwater runoff producing downstream floods, plus extensive soil ero-
sion and sedimentation problems. Both the altered hydrology and erosion mean
that downstream stretches have degraded water quality, aquatic habitats, and
fish populations. Solutions to these problems are tough and must address the
intermittent and tiny streams.
Larger streams are often channelized through farmland in urban regions,
but with narrow strips of riparian vegetation discontinuously distributed along
them. Widening and increasing the connectivity of these vegetated stream cor-
ridors is particularly valuable for wildlife habitat and movement.
Streams inbuiltareas suffer different fates (Paul and Meyer2001). Some
continue for stretches, but tend to be channelized or straightened with rock
or concrete ‘‘rip-rap” sides. In consequence, water velocity increases, channels
dry out in dry periods, and aquatic habitat and species diversity are drastically
reduced. Other streams disappear for stretches, or entirely, into concrete chan-
nels, or into underground pipes, where water rushes directly to a downslope
waterbody. The stream is gone. Sometimes the vegetated stream corridor along
a concrete channel or over the pipe also disappears, in this case to development.
In some cases the former stream corridor continues as a recreational greenway
or a seemingly abandoned green strip between communities. ‘‘Daylighting,” the
conversion of an underground piped water flow into a channelized or somewhat
curvy stream, is one solution occasionally achieved. Many designs and plans exist
toaddress this range of stream-corridor-in-built-area issues, but progress is slow
or negative.
In both the agricultural and built landscapes the surrounding land use nor-
mally has a much greater impact on streamwater quality than does the riparian
zone or vegetated stream corridor. Thus a range of fine-scale solutions over the
land is available and used in spots. Hedgerows, scattered trees, wooded patches,
grassy swales along intermittent channels, limited herbicide use, and other prac-
tices can noticeably decrease water and pollutant runoff from farmland. They
also increase habitat cover, diversity, and connectivity for biodiversity.
In built areas a stream is typically lined with adjacent house or other building
lots, which are designed and managed in extremely different ways. Thus dump-
ing, dogs, cats, yard fertilizers, insecticides, other chemicals, vegetation cutting,
erosion, septic seepage, trampling, and much more, varies markedly from lot to