Geomorphic effects of rural-to-urban land use conversion on three streams in the Central Redbed Plains of Oklahoma

This research evaluates the impact of rural-to-urban land use conversion on channel morphology and riparian vegetation for three streams in the Central Redbed Plains geomorphic province (central Great Plains ecoregion) of Oklahoma. The Deep Fork Creek watershed is largely urbanized; the Skeleton Creek watershed is largely rural; and the Stillwater Creek watershed is experiencing a rapid transition from rural to urban land cover. Each channel was divided into reaches based on tributary junctions, sinuosity, and slope. Field surveys were conducted at transects in a total of 90 reaches, including measurements of channel units, channel cross-section at bankfull stage, and riparian vegetation. Historical aerial photographs were available for only Stillwater Creek watershed, which were used to document land cover in this watershed, especially changes in the extent of urban areas (impervious cover).The three streams have very low gradients (< 0.001), width-to-depth ratios < 10, and cohesive channel banks, but have incised into red Permian shales and sandstone. The riparian vegetation is dominated by cottonwoods, ash, and elm trees that provide a dense root mat on stream banks where the riparian vegetation is intact. Channels increased in width and depth in the downstream direction as is normally expected, but the substrate materials and channel units remained unchanged. Statistical analyses demonstrated that urbanization did not explain spatial patterns of changes in any variables. These three channels in the central Redbed Plains are responding as flumes during peak flows, funneling runoff and the wash-load sediment downstream in major runoff events without any effect on channel dimensions. Therefore, local geological conditions (similar bedrock, cohesive substrates and similar riparian vegetation) are mitigating the effects of urbanization.     

Nitrogen mineralization potential in rewetted soils from a semi-arid stream landscape,north-west Australia

Drying-rewetting pulses stimulate nitrogen (N) mineralization in semi-arid systems and enhance N availability. Intermittent stream landscapes encompass a mosaic of soils of different textures and composition, and may support intense N transformation after rainfall. We modelled N mineralization potential by measuring accumulation of inorganic N (KCl extractable NO₃^? and NH₄⁺) in response to sustained flooding in soils from a small intermittent stream in semi-arid, north-west Australia. To test the relative importance of landscape position compared to flood pulse size, we incubated soils and sediments from six landscape positions, including three riparian vegetation types, rewetted to four different water potentials. Selected water potentials represented a light rain, heavy rain, single flood and successive flood event for the study site. The total amount of N mineralized was significantly affected by landscape position but not by saturation level. Riparian soils produced the greatest mineralization flush – over 70% of the total amount of N mineralized accumulated within 48 h of rewetting – however there was no difference among riparian vegetation types in N mineralization potential. N mineralized was a half to two-thirds lower in channel, floodplain and bank soils in comparison with riparian soils. We conclude that in systems subject to prolonged drought, N mineralization is predominantly determined by soil characteristics rather than the size of the rewetting pulse.     

Geomorphic Controls on Historical Channel Planform Changes on the Lower Pages River,Hunter Valley,Australia

Historical planform changes in a 14.7 km reach of the lower Pages River were determined to assess whether they were autogenic (inherent in the river regime) or allogenic (driven by external changes) in nature so as to better focus river management activities and river restoration works. A pattern metamorphosis or complete change in river morphology occurred during the February 1955 flood. The peak discharge of this event exceeded the slope and grain size (intrinsic) threshold for braiding, converting the narrow, slightly sinuous stream to a wide, braided-like river. Five subsequent intrinsic threshold-exceeding floods did not cause further bar development because an over-widened channel already existed. Autogenic channel planform changes included sinuosity variations due to lateral migration and pattern metamorphosis due to the exceedance of a discharge–slope–grain size geomorphic threshold. Allogenic channel planform changes included: (1) realignment/channel straightening and artificial cutoffs by river training works; (2) lateral migration by increased bank erodibility due to riparian vegetation clearing; (3) lateral migration by the operation of a transitive geomorphic threshold involving the onset of a flood-dominated regime after 1946 and increased catchment runoff after 1830 due to large-scale clearing of catchment vegetation; and (4) the occurrence of a large flood in February 1955. Multiple forcing factors have clearly caused historical channel planform changes of the lower Pages River, making the design of river management and restoration works a complex matter outside the scope of simple formulaic protocols.     

RIPARIAN VEGETATION AND SANDBAR MORPHOLOGY ALONG THE LOWER LITTLE COLORADO RIVER,ARIZONA

The distribution of riparian vegetation in relation to channel morphology is poorly understood in canyon rivers, which are characterized by in-channel fluvial sediment deposits rather than flood plains. This study focuses on vegetation and sandbar characteristics in two reaches of the lower Little Colorado River canyon in Arizona–one reach with ephemeral flow from the watershed, and another with perennial baseflow from a spring. Both reaches have been colonized by the exotic Tamarix chinensis, a riparian species known for its geomorphic influence on river channels. On the basis of a sampling of 18 bars, results show that vegetation frequency and density is significantly greater in the perennial study reach. However, sandbar morphology variables do not differ between reaches, despite a significantly narrower and deeper ephemeral channel. Hydraulic calculations of flood depths and Pearson correlations between bar and vegetation variables indicate reach-specific biogeomorphic relationships. In the ephemeral reach, higher bars are less affected by flood inundation, support older vegetation, and may be more stable habitat for vegetation. In the wider perennial reach where bars are lower and more expansive, vegetation patterns relate to bar size, Tamarix being most common on the largest bars. Overall results suggest that (1) vegetation variation relates to baseflow hydrology, (2) bar formation relates to high discharge events, and (3) vegetation patterns respond to, rather than influence, sandbar form in this canyon riparian system.     

Recent large-magnitude floods and their impact on valley-floor environments of northeastern Yellowstone

The Lamar River watershed of northeastern Yellowstone contains some of the most diverse and important habitat in the national park. Broad glacial valley floors feature grassland winter range for ungulates, riparian vegetation that provides food and cover for a variety of species, and alluvial channels that are requisite habitat for native fish. Rapid Neogene uplift and Quaternary climatic change have created a dynamic modern environment in which catastrophic processes exert a major influence on riverine–riparian ecosystems. Uplift and glacial erosion have generated high local relief and extensive cliffs of friable volcaniclastic bedrock. As a result, steep tributary basins produce voluminous runoff and sediment during intense precipitation and rapid snowmelt. Recent major floods on trunk streams deposited extensive overbank gravels that replaced loamy soils on flood plains and allowed conifers to colonize valley-floor meadows. Tree-ring dating identifies major floods in 1918, ca. 1873, and possibly ca. 1790. In 1996 and 1997, discharge during snowmelt runoff on Soda Butte Creek approached the 100-year flood estimated by regional techniques, with substantial local bank erosion and channel widening. Indirect estimates show that peak discharges in 1918 were approximately three times greater than in 1996, with similar duration and much greater flood plain impact. Nonetheless, 1918 peak discharge reconstructions fall well within the range of maximum recorded discharges in relation to basin area in the upper Yellowstone region. The 1873 and 1918 floods produced lasting impacts on the channel form and flood plain of Soda Butte Creek. Channels may still be locally enlarged from flood erosion, and net downcutting has occurred in some reaches, leaving the pre-1790 flood plain abandoned as a terrace. Gravelly overbank deposits raise flood-plain surfaces above levels of frequent inundation and are well drained, therefore flood-plain soils are drier. Noncohesive gravels also reduce bank stability and may have persistent effects on channel form. Overall, floods are part of a suite of catastrophic geomorphic processes that exert a very strong influence on landscape patterns and valley-floor ecosystems in northeastern Yellowstone.     

国内外河岸带研究的进展与展望

本文从河岸带研究的重要性入手,在河岸带内不同要素的相互作用机制,河岸植被带的功能、有效宽度、生态建设和规划管理,河岸带土地利用,河岸带数据提取分析以及集成研究等方面初步探讨了国内外河岸带研究的现状。在此基础上分析了当前研究中存在的问题和不足之处,指出针对不同地域的典型样带开展对比研究、选择适宜的景观分析方法和改进数据分析技术是今后河岸带研究的发展趋势。     

Medium and short-term channel planform changes on the Rivers Tay and Tummel, Scotland

Channel planform change was analysed using a variety of data-sources for the medium-term (>25 years and <250 years) and short-term (<25 years) on a reach of the Rivers Tay and Tummel, Scotland. Map data were input into a Geographic Information System (GIS) and used to determine planform characteristics and changes in width, braiding index and sinuosity for the study reach between 1755 and 1976. Aerial photographs were utilised to determine the more recent changes that had taken place between 1971 and 1994. The analysis showed that significant changes had occurred over the medium term with a mean reduction in channel width of 34% for this period. These changes are comparable to those found in studies of similar European rivers for this period. Changes determined for the short-term displayed a continuance of this trend at a comparable rate of change. An analysis of flood frequency and magnitude, precipitation and discharge records for both periods does not show an associated decrease and therefore does not reflect the changes in channel planform. Evidence points towards flood embankment construction in the mid-1800s as the initial cause of channel change for the study reach which was later exacerbated by flow regulation. Incision and the subsequent stabilisation of lateral and mid-channel gravel bars by vegetation succession has resulted in an overall increase in the stability of the study reach which has persisted even where the embankments have fallen into disrepair.     

河岸带及其生态重建研究

河岸带具有重要的生态、社会、经济和旅游价值。河岸带研究以生态学、水文学和地貌学为基础涉及多种学科和技术。我国河岸带及其退化生态系统重建理论与实践研究均较为薄弱。本文基于 6年河岸带退化生态系统重建的科学研究实践 ,阐述了河岸带研究的意义、内容及其生态、经济和社会效能 ;分析了河岸带生态重建的理论与技术方法 ,探讨了河岸带滩地生态重建的措施及河岸带今后管理的目标、原则和方向 ,并以皖天柱山麓潜水河岸带滩地生态重建为例进行了验证     

Conflation and aggregation of spatial data improve predictive models for species with limited habitats: A case of the threatened yellow-billed cuckoo in Arizona,USA

Riparian vegetation provides important wildlife habitat in the southwestern United States, but limited distributions and spatial complexity often leads to inaccurate representation in maps used to guide conservation. We test the use of data conflation and aggregation on multiple vegetation/land-cover maps to improve the accuracy of habitat models for the threatened western yellow-billed cuckoo (Coccyzus americanus occidentalis). We used species observations (n = 479) from a state-wide survey to develop habitat models from 1) three vegetation/land-cover maps produced at different geographic scales ranging from state to national, and 2) new aggregate maps defined by the spatial agreement of cover types, which were defined as high (agreement = all data sets), moderate (agreement ≥ 2), and low (no agreement required). Model accuracies, predicted habitat locations, and total area of predicted habitat varied considerably, illustrating the effects of input data quality on habitat predictions and resulting potential impacts on conservation planning. Habitat models based on aggregated and conflated data were more accurate and had higher model sensitivity than original vegetation/land-cover, but this accuracy came at the cost of reduced geographic extent of predicted habitat. Using the highest performing models, we assessed cuckoo habitat preference and distribution in Arizona and found that major watersheds containing high-probably habitat are fragmented by a wide swath of low-probability habitat. Focus on riparian restoration in these areas could provide more breeding habitat for the threatened cuckoo, offset potential future habitat losses in adjacent watershed, and increase regional connectivity for other threatened vertebrates that also use riparian corridors.     

Patterns of vegetation greenness during flood,rain and dry resource states in a large,unconfined floodplain landscape

Floodplains are multi-state systems in which vegetation distribution is associated with the presence or absence of water as a resource. Less is known about the associations between the presence and absence of water and vegetation productivity. We examined patterns of vegetation productivity in a large (10 519 km²) unconfined floodplain during flood, rain and dry resource states. Mosaics of vegetation greenness were derived at two scales using the Normalized Difference Vegetation Index: a whole-of-landscape scale and a geomorphic unit scale with a riparian and floodplain unit. The NDVI was also calculated within a-priori vegetation community types within the floodplain. In all resource states over 50% of the floodplain showed no discernible vegetation greenness. When water is added as rain or flooding vegetation greenness increases, but the highest greenness occurs in the flood state. Trees situated in the riparian geomorphic unit maintain greenness during the dry resource state, whereas grasses situated in the floodplain contribute greenness during rain and flood resource states, with the highest greenness in the flood resource state. Aligned with views that dryland floodplains are boom-bust ecosystems, we suggest that flooding is a fundamental driver of vegetation productivity in this unconfined floodplain, contributing functional heterogeneity to the landscape.     

喜马拉雅中部甘达基河流域尼泊尔国鸟(棕尾虹雉)生境分布变化

甘达基河流域(Gandaki River Basin,GRB)是喜马拉雅中部地区的一部分,该地区栖息着许多珍稀的野生动物。由于气候和人类活动的影响,许多珍稀保护物种的生境处于危险之中。本研究基于最大熵(MaxEnt)模型,运用生物气候、土地覆被和DEM数据,分析各环境要素对棕尾虹雉(Lophophorusimpejanus)的生境适宜性的影响,评估棕尾虹雉现在状况和未来栖息地分布的变化。研究表明,目前棕尾虹雉的高度适宜栖息地面积约为749 km^2,主要分布在流域北部、东部和西部,尤其是郎塘国家公园、马纳斯卢峰自然保护区和安纳布尔纳峰自然保护区等保护区内。到2050年,棕尾虹雉的高度适宜栖息地面积将减少至561 km^2,主要在流域北部和西北部(即Chhyo,Tatopani,Humde和Chame地区)。未来环境变化的模拟表明,由于适宜栖息地面积的减少,棕尾虹雉面临的生存风险将增加。     

Allogenic and autogenic influences upon riparian vegetation dynamics

Riparian vegetation dynamics are regarded as being driven by allogenic hydrogeomorphological factors, with autogenic (plant-induced) influences becoming more important as landform stability is achieved. Autogenic processes, however, may have a substantial influence on both plant dynamics and the river environment from the earliest stages of plant establishment. Various aspects of both allogenic and autogenic processes in riparian vegetation dynamics are discussed here; in particular how plants may promote bank stability and sedimentation, and river island development. Riparian restoration often fails to incorporate autogenic processes, thereby restricting the re-establishment of natural functioning, and further interdisciplinary work is needed to address this.     

Effects of dam operation and land use on stream channel morphology and riparian vegetation

Dams are well known for influencing channel and vegetation dynamics downstream, but little work has focused on distinguishing effects of land use and channel responses to the impoundment. In this paper, we examined interacting effects of a dam and land use on downstream changes in channel morphology and riparian vegetation along an agricultural stream system in northern California. Measurements of planform channel morphology, vegetation area, and land use were mapped along multiple stream segments based on a chronological sequence of historical aerial photographs over a 34-yr period prior to operation of the dam in 1983 and over a 17-yr period after dam operation, and compared to a nearby, undammed reference stream. A two-factor analysis of covariance (ANCOVA) was used to examine the effect of the dam on changes in bankfull area, stream length, and riparian vegetation area while accounting for the effect of land use and distance downstream. The dammed stream's bankfull area contracted 94% after dam operation. Prior to dam operation, bankfull area decreased when land use area increased, but not after operation of the dam. Stream length varied 64% less after dam operation as a consequence of less frequent episodic channel migration and entrenchment. The area of riparian vegetation was decreasing during the pre-dam period, but then increased 72% after operation of the dam. Across time periods, decreases in the area of riparian vegetation were also associated with increases in land use area in both the dammed and reference stream. After operation of the dam, reduced peak discharges and sediment reduction likely lead to channel incision and constrained channel migration, which allowed vegetation to increase 50% on less accessible, abandoned banks. Rating curve and hydraulic exponent analyses based on stream gauge measurements corroborate statistical analyses of the mapped changes. In conclusion, we found that operation of the dam and land use patterns together influenced spatial and temporal changes in channel morphology and riparian vegetation. Use of a nearby undammed reference stream in conjunction with multivariable analysis of spatially and temporally replicated observations provided an effective framework for unraveling interacting effects of dams and land use activities on stream channel and vegetation dynamics.     

Channel incision and patterns of cottonwood stress and mortality along the Mojave River, California

In 1995, mapping and classification of riparian vegetation along the Mojave River in southern California revealed an 8-km reach in which riparian cottonwoods (Populus fremontii Wats.) were stressed or dying. We tested a set of predictions based on the inference that cottonwood decline was an indirect result of lowered water-table levels following flood-related channel incision. Comparisons of topographic cross-sections from 1963 and 1997, indicated a net change in channel elevation between −0·71 and −3·6 m within zones of cottonwood stress and mortality. Ages of young cottonwood and willow stems adjacent to the present channel and radial stem growth of surviving cottonwoods were consistent with the inference that channel incision, associated with sustained flooding in January and February of 1993, lowered channel elevations throughout the affected reach. Well records and soil redoximorphic features indicate that channel incision caused net water-table declines 1·5 m on portions of the adjacent flood plain where cottonwood stand mortality ranged between 58 and 93%. In areas where water-table declines were estimated to be <1·0 m, stand mortality was 7–13%.     

Late Holocene upper bounds of flood magnitudes and twentieth century large floods in the ungauged, hyperarid alluvial Nahal Arava, Israel

The impact of large twentieth century floods on the riparian vegetation and channel morphology of the relatively wide anabranching and braided Nahal Arava, southern Israel, was documented as part of developing tools to (a) identify recent large floods, (b) determine these flood's respective magnitudes in alluvial ungauged streams, and (c) determine long-term upper bounds to flood stages and magnitudes. Along most of its course Nahal Paran, a major tributary that impacts the morphology, floods and sediments of Nahal Arava at the study reach, is a coarse-gravel, braided ephemeral stream. Downstream of the Arava–Paran confluence, aeolian and fluvial sand delivered from eastern Arava valley alters the channel morphology. The sand has accreted up to 2.5 m above the distinct current channels, facilitating the recording of large floods. This sand enhances the establishment of denser riparian vegetation (mainly Tamarix nilotica and Haloxylon persicum) that interacts with floods and affects stream morphology. A temporal association was found between specific floods recorded upstream and tree-ring ages of re-growth of flood-damaged tamarix trees (‘Sigafoos trees’) in the past 30 years. This association can be utilized for developing a twentieth century flood chronology in hyperarid ungauged basins in the region. The minimum magnitude of the largest flood that covered the entire channel width, estimated from flood deposits, is approximately 1700–1800 m³s^− 1. This is a larger magnitude than the largest gauged flood of 1150 m³s^− 1 that occurred in 1970 about 30 km upstream in Nahal Paran. Our estimation agrees with flood magnitude estimated from the regional envelope curve of the largest floods. Based on Holocene alluvial stratigraphy and OSL dating in the study reach we also conclude that flood stages did not reach the late Holocene ( 2.2 ka) surface and therefore we estimate a non-exceedance upper bound of  2000 m³s^− 1 flood magnitudes for Nahal Arava during that interval. This study indicates that in unfavorable areas the combination of hydrology, fluvial morphology and botanic evidence can increase our understanding of ungauged basins and give information crucial for hydrology planning.     

Medium‐term fluvial island evolution in a disturbed gravel‐bed river (Piave River,Northeastern Italian Alps)

River islands are defined as discrete areas of woodland vegetation surrounded by either water‐filled channels or exposed gravel. They exhibit some stability and are not submerged during bank‐full flows. The aim of the study is to analyze the dynamics of established, building, and pioneer islands in a 30‐km‐long reach of the gravel‐bed Piave River, which has suffered from intense and multiple human impacts. Plan‐form changes of river features since 1960 were analyzed using aerial photographs, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces, and maximum and mean height of their vegetation. The results suggest that established islands lie at a higher elevation than building and pioneer islands, and have a thicker layer of fine sediments deposited on their surface after big floods. After the exceptional flood in 1966 (RI > 200 years) there was a moderate increase in island numbers and extension, followed by a further increase from 1991, due to a succession of flood events in 1993 and 2002 with RI > 10 years, as well as a change in the human management relating to the control of gravel‐mining activities. The narrowing trend (1960–1999) of the morphological plan form certainly enhanced the chance of islands becoming established and this explains the reduction of the active channel, the increase in established islands and reduction of pioneer islands.     

The Current Status of Riparian Vegetation along Bank of Kelantan River after the Worst Flood for Decades

Undeniably Kelantan is one of the east coast states of Malaysia,which has faced yearly flooding catastrophe especially during north-east-monsoon season.The aims of this study are to record the land uses from upstream to downstream of Kelantan River basin,and to record the riparian vegetation that are resistance and susceptible to flood situations in affected areas along the bank of Kelantan River after December 2014 when the worst flood was recorded for decades.A serial of surveys were conducted at 9 sampling sites(S1 to S9)from the upstream to the downstream in the basin.The massive clearing in the forest in the basin particularly in the upper streams was a serious problem.Heavy loads of sedimentations greatly affected the hydrological system of Kelantan River.There were 64 plant species were recorded in this study.Most sampling sites were submerged and most of the riparian plants survived although the flood levels reached 10 m.On the other hand,some commercial tree species such as Elaeis guenensis,Lansium parasiticum and Nephelium lappaceum could not thrive in flooding conditions.It should be noted that the populations of noxious,such as Mimosa pigra and Piper aduncum had colonized most parts of riparian zones.Perhaps due to the disturbances of catchment and riparian vegetations,the river water regimes have been transformed.Therefore,the ecological assessments and socio-economic approaches were recommended in order to mitigate the flood situation.     

Spatial hydrogeomorphological influences on sediment and nutrient deposition in riparian zones: observations from the Garonne River,France

This paper investigates the influence of geomorphological setting on riparian zone sedimentation within a reach of the River Garonne, France, during three major floods. The sampling design was stratified to reflect landforms constructed by fluvial processes (e.g. floodplain, lateral benches, islands, side channels and point bars). Observed sedimentation varied significantly with flood event, planform context, landform type and associated vegetation cover and, in some cases, with sample location within the landform. Lowest sedimentation was associated with the flood with the smallest peak discharge, peak sediment concentration and sediment load. Sites under natural riparian vegetation experienced higher sedimentation than poplar plantations. Sites on concave (outer) banks received less sedimentation than those on convex (inner banks). Sedimentation on floodplain sites and higher benches was lower than on low benches, point bars and side channels. There was considerable interdependence among these patterns, reflecting the underlying geomorphological forms and processes. Meandering rivers tend to evolve through erosion of concave banks and deposition on convex banks. Point bar features tend to be built along convex banks, whilst concave banks are eroded into higher floodplain and bench features. As a result, concave banks tend to be bordered by higher riparian margins that are less frequently flooded than convex banks. Where river margins are developed for agriculture, the higher, less frequently flooded sites are preferentially selected.Analyses of the quantity, calibre, nutrient and carbon content of the deposited sediment reveal further significant relationships, which reflect the geomorphological structure of the riparian zone. Sediment particle size coarsens in locations with higher amounts of sedimentation. The quantities of total organic carbon (TOC), total organic nitrogen (TON) and total phosphorus (TP) all increase as the quantity of deposited sediment increases. The concentration of TOC and TON also increased significantly with an increase in the percentage of silt plus clay in the deposited sediments.Based upon the above observations, a conceptual model is proposed, which considers the spatial pattern in riparian zone sedimentation according to riparian morphology and flood magnitude. The implications of channel incision for the functioning of the model are also discussed.     

Interaction of ENSO-driven Flood Variability and Anthropogenic Changes in Driving Channel Evolution: Corryong/Nariel Creek,Australia

Understanding the relative contributions of climatic and anthropogenic drivers of channel change are important to inform river management, especially in the context of environmental change. This global debate is especially pertinent in Australia as catchments have been severely altered since recent European settlement, and there is also strong evidence of cyclical climate variability controlling environmental systems. Corryong/Nariel Creek is an ideal setting to further study the interaction between climate and anthropogenic changes on channel evolution as it has experienced both significant periods of flood and drought, controlled by the El Niño Southern Oscillation (ENSO), and extensive anthropogenic changes. Since European settlement the floodplain has been completely cleared, the riparian zone almost entirely invaded by willows, and every reach of the channel has experienced some form of direct channel modification. Through the combined analysis of channel evolution, climate changes and anthropogenic history of the river it was found that both the ENSO-driven climate and anthropogenic drivers are significant, although at different scales of channel change. Significant straightening in response to land clearing in the early twentieth century occurred before any records of direct channel modifications. Following this, most river management works were in response to instabilities created in the clearing period, or to instabilities created by flooding triggering a new phase of instability in reaches which had already undergone stabilisation works. Overall, human activities triggered channel instability via land clearing, and management works since then generally exacerbated erosion during high flows that are driven by climate fluctuations. This research raises the interesting question of whether rivers in Australia have become more responsive to the ENSO cycle since the clearing of catchment and riparian vegetation, or whether the past response to climate variability was different.     

Riparian reforestation and channel change: A case study of two small tributaries to Sleepers River, northeastern Vermont, USA

Measurements of two small streams in northeastern Vermont, collected in 1966 and 2004–2005, document considerable change in channel width following a period of passive reforestation. Channel widths of several tributaries to Sleepers River in Danville, VT, USA, were previously measured in 1966 when the area had a diverse patchwork of forested and nonforested riparian vegetation. Nearly 40 years later, we remeasured bed widths and surveyed large woody debris (LWD) in two of these tributaries, along 500 m of upper Pope Brook and along nearly the entire length (3 km) of an unnamed tributary (W12). Following the longitudinal survey, we collected detailed channel and riparian information for nine reaches along the same two streams. Four reaches had reforested since 1966; two reaches remained nonforested. The other three reaches have been forested since at least the 1940s. Results show that reforested reaches were significantly wider than as measured in 1966, and they are more incised than all other forested and nonforested reaches. Visual observations, cross-sectional surveys, and LWD characteristics indicate that reforested reaches continue to change in response to riparian reforestation. The three reaches with the oldest forest were widest for a given drainage area, and the nonforested reaches were substantially narrower. Our observations culminated in a conceptual model that describes a multiphase process of incision, widening, and recovery following riparian reforestation of nonforested areas. Results from this case study may help inform stream restoration efforts by providing insight into potentially unanticipated changes in channel size associated with the replanting of forested riparian buffers adjacent to small streams.