9446

• UCREFRP Catalog Number: 9446
• Author: Stanford, J. A., J. V. Ward, W. J. Liss, C. A. Frissell, R. N. Williams, J. A. Lichatowich and C. C. Coutant
• Title: A General Protocol for Restoration of Regulated Rivers
• USFW Year: 1996
• USFW - Doc Type: Regulated Rivers
• Copyright Material: YES

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j, A, STANFORD ET AL

strong interactors capable of structuring food-webs: Power et al., 1995) may clarify spatial and temporal
scales in large river restorations,
In general, the entire catchment, from headwaters to the ocean, is relevant. In the case of rivers that sup-
port anadromous fisheries, estuarine and ocean habitats connect functionally to the riverine components,
Mathematical models can be used very effectively to formalize understanding of the effects of regulation
and interactions with pollution and food-web manipulation within the river continuum, but models should
not be used exclusively to define a restoration strategy (Hall, 1 988b). The process must be inferential from the
entire body of quantitative and qualitative information about how river regulation and interactive effects
have altered ecosystem capacity.

Restore environmental (habitat) heterogeneity but let the river do the work

The main goal is to reduce the range of human disturbances so that interconnected riverine habitats (Fig-
ures I and 2) can support diverse and productive food-webs, including species of special social and economic
interest. Management should strive to restore environmental heterogeneity and reduce or eliminate sources
of mortality from pollution and overharvest. Keep in mind that riverine biodiversity and bioproduction are
largely controlled by ,abiotic drivers (Figure 3) and that density-dependent relationships, such as the stock-
recruitment relations often used to determine fisheries harvest prescriptions, rarely manifest predictably
owing to natural abiotic variation (Hall, 1986; Hall, 1988a; Pimm, 1991; Huston, 1994).
Owing to the importance of flow to habitat maintenance, and temperature to food-web energetics, highly
significant restoration is possible simply by reregulation to allow more natural seasonality of flow and tem-
perature. We call this restoration of normative habitat conditions, where the norm or standard is established
from what is possible in a natural-cultural context as opposed to striving for pristine conditions which are
difficult, if not impossible, to define or achieve, at least for entire catchments, Removal of dams certainly
should be considered and, where possible, done; but, restoration of normative habitat conditions is possible
in many if not most regulated rivers without taking dams out. However, channel revetments are problematic
because the objective is to reconnect channels and floodplains.
Peak flows are needed to scour and rearrange substratum and reconnect floodplain habitats with the chan-
nel; spatial and temporal temperature variability promotes re-establishment of native biodiversity (Figures 2
and 5), Peak flows needed to re-establish cut and fill alluviation (called effective flows by geomorphologists)
mayor may not be equal to bank-full, and gravel supply may be limiting owing to storage of bedload in the
reservoirs (Ligon et aI" 1995), Effective flows can rapidly degrade (downcut) entire segments when sediment
mass balance relations change as a consequence of regulation (Andrews and Nelson, 1989). Adding sedi-
ments to regulated rivers (e,g, using slurry pipelines from reservoir deltas) should not be out of the realm
of consideration in situations where instream sediment supply is limited by years of regulation, However,
overbank flows in many cases will initiate cut and fill alluviation in an ecologically effective manner, supply-
ing sufficient sediment from lateral erosion,
We emphasize that reregulation of flows requires careful evaluation of channel morphometry, bed-sedi-
ment size distribution and shear stress in relation to the range of possible flows, A great deal of geomorpho-
logical study and modelling has been devoted to this problem in recent years (Andrews, 1980; Andrews and
Nelson, 1989; Kellerhals and Church, 1 989; Deitric~ et aI., 1993; Church, 1995) and more work is needed, In
general, flows that mobilize substrata of median particle diameter will build bars, cut overflow channels and
dig pools, Determination of peak flows is complicated by dense, often senescent, thickets of riparian
vegetation on the floodplains of regulated rivers, Repeated scouring flows will most likely restore riparian
successional vitality. Annual temperature patterns similar to pre-regulation conditions, which will directly
mediate restoration of biota, can often be attained by depth selective withdrawal structures on the dams
(Gore, 1985),
Of course, restoration of overbank flows may be problematic in many rivers where humans have colonized
the floodplains. In these cases, revetments have often been extensively built to restrain flood flows, Reregu-
lation to produce overbank flows may not be practical. However, floods of record will most likely result in
overbank flow even in intensely regulated rivers, because natural storage on floodplains throughout the con-
tinuum has been drastically diminished, Revetments tend to act as dams during very large floods on