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If you wanted to conjure an image of a perfect summer day – perhaps picnicking by a meandering stream, the fragrance of wildflowers borne by a warm breeze as butterflies flicker across your vision and trout slurp mayflies in lazily spreading pools – you could do no better than visualize the mountain meadows of northern New Mexico. Anyone who has taken the trouble to reach these often inaccessible miniature Edens knows instinctively that they are some of the most ecologically productive places in the Southwest.

Amigos Bravos has been working to protect one such special area – the Valle Vidal in the Costilla watershed just south of the Colorado border. Here the vast Valle itself (source of the headwaters of Comanche Creek) retains some of its primeval grandeur, leading the eye across sweeping grasslands toward aspen groves and stands of dark spruce on distant, encircling hills. The creek is anothermatter, though. In one meadow it has retained its intricate sinuosity, but has cut down and widened so the once lively flow is now stagnant and lifeless; in another, further downstream, the channel is wide and shallow and the banks are raw and eroding – exposing the peaty soil formed under the higher watertable conditions of this former wet meadow, which now looks increasingly parched and bare.

Many of the mountain meadow streams in the Southwest are like this. Logging and associated roads have altered hydrographs and increased sedimentation, while intensive grazing has created erosion of its own and destroyed crucial bankside vegetation. Even in the magnificent valles of the new Valles Caldera National Preserve, where the public has until now only viewed the meadow streams from a longing distance, the creeks are degraded, producing sediment and high summer temperatures which lead to water quality impairments further downstream.

Amigos Bravos is partnering with the Truchas Chapter of Trout Unlimited to sponsor a workshop aimed at understanding, and finding the commonalities between, these high meadow stream systems. The word system is important: the precise characteristics of each stream – its ‘planform’ pattern when viewed from above, its cross-sectional proportions, its bed material and its flow patterns – are dependent on a set of linked determinants such as valley slope and hydrograph. We need a comprehensive-enough grasp of these linked parameters to understand why the stream looks the way it does – and, in the case of degraded systems, how far away it is from its potential. Inadequate understanding of this complexity – or a failure to piece together the ‘architecture of complexity’, as it has been called – has led to numerous failed stream restoration projects which very often exacerbated the original problem or created new, unanticipated ones.

Fortunately, others have already done a good deal of the necessary scientific work for us. Dave Rosgen, a geomorphologist from southern Colorado, has spent many years devising a classification system for stream-types which groups them for their dominant morphologies and the processes that produce these patterns. The classification system
provides a shorthand for describing, and a shortcut for understanding, generally similar streamtypes. For example, many undisturbed high meadow streams would be given a ‘Rosgen E’ classification, referring to a sinuous planform (reflecting low valley slope and easily eroded alluvial substrates) and a relatively deep, clean channel (reflecting strong vegetation to hold the banks, and a high sediment transport capacity). Bank vegetation, which also filters out flood sediment, is a key to keeping these streamtypes intact – without it, rapid channel widening and straightening will take place, with increases in effective gradient, downcutting, abandonment of the floodplain and lowering of the watertable: exactly what has occurred on Comanche Creek. The driving determinants of the system are such, though, that (with the sources of destabilization substantially removed) the stream will attempt to regain its former overall morphology, establishing a secondary floodplain and regaining its sinuosity and relative depth. (Unfortunately this could take decades or centuries, however.) Rosgen helpfully describes typical ‘evolutionary’ scenarios which have followed large-scale man-made (and climatic) disturbances.

Our workshop will attempt to apply these insights both to Comanche and to the Valles Caldera meadow streams. The analysis will highlight appropriate (and inappropriate) restoration methods for these degraded creeks – and particularly the stabilizing role of bank vegetation. We believe these systems, running over alluvial substrates and with seasonally high flows, are naturally highly dynamic: even though an established ‘E’ streamtype morphology will persist in ‘dynamic equilibrium’, it will be changing in detail all the time. Vegetation can stabilize and reduce the rate of change, while being flexible and adaptable enough to accommodate the dynamics (unlike ‘hard’
engineered structures which will be quickly abandoned by a migrating channel).

Those who work in stream restoration need to be adaptable too – in the sense that we just do not understand enough about the complexity of these dynamic systems NOT to monitor the results of changes we impose, thereby learning their precise impacts and adapting them accordingly. We need to approach this complexity with humility and care; a properly controlled experimental approach, which does not over-commit on a large scale before there is adequate knowledge, is the soundest scientific route.

As author Tom McGuane observed, “Rivers once had everything they needed. They were the paragon of creation.” We stumble toward giving them back what they need – and letting them re-create themselves.