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1.
Predicting runoff and erosion from watersheds burned by wildfires requires an understanding of the three-dimensional structure of both hillslope and channel drainage networks. We investigate the small- and large-scale structures of drainage networks using field studies and computer analysis of 30- m digital elevation model. Topologic variables were derived from a composite 30-m DEM, which included 14 order 6 watersheds within the Pikes Peak batholith. Both topologic and hydraulic variables were measured in the field in two smaller burned watersheds （3.7 and 7.0 hectares） located within one of the order 6 watersheds burned by the 1996 Buffalo Creek Fire in Central Colorado. Horton ratios of topologic variables （stream number, drainage area, stream length, and stream slope） for small-scale and large-scale watersheds are shown to scale geometrically with stream order （i.e., to be scale invariant）. However, the ratios derived for the large-scale drainage networks could not be used to predict the rill and gully drainage network structure. Hydraulic variables （width, depth, cross- sectional area, and bed roughness） for small-scale drainage networks were found to be scale invariant across 3 to 4 stream orders. The relation between hydraulic radius and cross-sectional area is similar for fills and gullies, suggesting that their geometry can be treated similarly in hydraulic modeling. Additionally, the rills and gullies have relatively small width-to-depth ratios, implying sidewall friction may be important to the erosion and evolutionary process relative to main stem channels.  相似文献   

2.
Fallout radionuclides (FRNs) 137Cs and 210Pb are well established as tracers of surface and sub‐surface soil erosion contributing sediment to river systems. However, without additional information, it has not been possible to distinguish sub‐surface soil erosion sources. Here, we use the FRN 7Be (half‐life 53 days) in combination with 137Cs and excess 210Pb to trace the form of erosion contributing sediment in three large river catchments in eastern Australia; the Logan River (area 3700 km2), Bowen River (9400 km2) and Mitchell River (4700 km2). We show that the combination of 137Cs, excess 210Pb and 7Be can discriminate horizontally aligned sub‐surface erosion sources (rilled and scalded hillslopes and the floors of incised drainage lines and gully ‘badland’ areas) from vertical erosion sources (channel banks and gully walls). Specifically, sub‐surface sources of sediment eroded during high rainfall and high river flow events have been distinguished by the ability of rainfall‐derived 7Be to label horizontal soil surfaces, but not vertical. Our results indicate that in the two northern catchments, erosion of horizontal sub‐surface soil sources contributed almost as much fine river sediment as vertical channel banks, and several times the contribution of hillslope topsoils. This result improves on source discrimination provided previously and indicates that in some areas erosion of hillslope soils may contribute significantly to sediment yield, but not as topsoil loss. We find that in north‐eastern Australia, scalded areas on hillslopes and incising drainage lines may be sediment sources of comparable importance to vertical channel banks. Previous studies have used the combination of 137Cs, excess 210Pb and 7Be to estimate soils losses at the hillslope scale. Here, we show that with timely and judicious sampling of soil and sediment during and immediately after high flow events 7Be measurements can augment fallout 137Cs and 210Pb to provide important erosion source information over large catchments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

3.
High and moderate severity wildfires should increase sediment production from unpaved roads due to the increased surface runoff from upslope, and increase road–stream connectivity due to the decrease in downslope surface roughness as well as the increase in surface runoff and erosion. Because no study has documented these effects, we surveyed road surface erosion features and quantified road–stream connectivity as a function of fire severity and road segment characteristics. The data were collected one year after the High Park wildfire from 141 hydrologically distinct road segments along 6.8 km of an unpaved road west of Fort Collins, Colorado. Road segments below areas burned at high and moderate severity had significantly more rills than road segments below areas that burned at low severity. Road segment slope was an important control on the proportion of segment length with rills, and the strength of the relationship between road segment slope and the amount of rilling increased with burn severity. Flatter road segments tended to capture the sediment eroded from upslope burned areas. In areas burned at high and moderate severity all of the road segments had drainage features extending to a stream, and 78% of the segments in areas burned at low severity also were connected. These exceptionally high rates of road–stream connectivity are attributed to the increased runoff from upslope, the segment‐scale collection and funneling of hillslope and road surface runoff to a single drainage point, and the reduced infiltration and trapping capacity of the burned area below the road. The results show the need to either outslope the roads or increase the frequency of constructed drainage features after wildfires, particularly for steeper road segments in areas burned at high or moderate severity. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

4.
In July 2013, a wildfire severely affected the western part of the island of Mallorca (Spain). During the first three post‐fire hydrological years, when the window of disturbance tends to be more open, the hydrological and sediment delivery processes and dynamics were assessed in a representative catchment intensively shaped by terracing that covered 37% of its surface area. A nested approach was applied with two gauging stations (covering 1.2 km2 and 4.8 km2) built in September 2013 that took continuous measurements of rainfall, water and sediment yield. Average suspended sediment concentration (1503 mg L?1) and the maximum peak (33 618 mg L?1) were two orders of magnitude higher than those obtained in non‐burned terraced catchments of Mallorca. This factor may be related to changes in soils and the massive incorporation of ash into the suspended sediment flux during the most extreme post‐fire event; 50 mm of rainfall in 15 min, reaching an erosivity of 2886 MJ mm ha?1 h?1. Moreover, hysteretic counter‐clockwise loops were predominant (60%), probably related to the increased sensitivity of the landscape after wildfire perturbation. Though the study period was average in terms of total annual precipitation (even higher in intensities), minimal runoff (2%) and low sediment yield (6.3 t km?2 y?1) illustrated how the intrinsic characteristics of the catchment, i.e. calcareous soils, terraces and the application of post‐fire measures, limited the hydrosedimentary response despite the wildfire impact. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

5.
The relationship between stream water DOC concentrations and soil organic C pools was investigated at a range of spatial scales in subcatchments of the River Dee system in north‐east Scotland. Catchment percentage peat cover and soil C pools, calculated using local, national and international soils databases, were related to mean DOC concentrations in streams draining small‐ (<5 km2), medium‐ (12–38 km2) and large‐scale (56–150 km2) catchments. The results show that, whilst soil C pool is a good predictor of stream water DOC concentration at all three scales, the strongest relationships were found in the small‐scale catchments. In addition, in both the small‐ and large‐scale catchments, percentage peat cover was as a good predictor of stream water DOC concentration as catchment soil C pool. The data also showed that, for a given soil C pool, streams draining lowland (<700 m) catchments had higher DOC concentrations than those draining upland (>700 m) catchments, suggesting that disturbance and land use may have a small effect on DOC concentration. Our results therefore suggest that the relationship between stream water DOC concentration and catchment soil C pools exists at a range of spatial scales and this relationship appears to be sufficiently robust to be used to predict the effects of changes in catchment soil C storage on stream water DOC concentration. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

6.
The Holocene volumetric sediment budget is estimated for coarse textured sediments (sand and gravel) in a large, formerly glaciated valley in southwest British Columbia. Erosion is estimated by compiling volumetric loss estimated in digital elevation models (DEMs) of gullied topography and by applying a non‐linear diffusion model on planar, undissected hillslopes. Estimates of steepland yield are based on estimates of post‐glacial deposition volumes in fans, cones and deltas at the outlets of low‐order tributary catchments. Erosion of post‐glacial fans and tributary valley fills is estimated by reconstructing formerly continuous surfaces. Results are classed by catchment order and compared across scales of contributing area, revealing declining specific sediment yield (in m3 km?2 a?1) with catchment area for the smaller tributaries (<10 km2) and increasing specific sediment yield for larger tributaries and Chilliwack Valley itself. Approximately 60% of mobilized sediment is redeposited in first‐ to third‐order catchments, with lesser proportions stored at the outlets of higher order catchments. A simple network routing model emphasizes the significant sediment flux contributions from colluvium, drift blankets and gullies in steeper terrain. As this material is deposited at junctions within the lower drainage network, an increasing proportion of material is derived from remnant valley fills and para‐glacial fans in the major valleys. Yield from lower‐order, steepland catchments tends to remain in storage, indefinitely sequestered on footslopes. These observations have implications for modelling the post‐glacial sediment balance amongst catchments of varying size. After 104 years, the system remains in disequilibrium. The critical linkage lies between low‐order, hillslope catchments (相似文献   

7.
Understanding the role of forest fires on water budgets of subarctic Precambrian Shield catchments is important because of growing evidence that fire activity is increasing. Most research has focused on assessing impacts on individual landscape units, so it is unclear how changes manifest at the catchment scale enough to alter water budgets. The objective of this study was to determine the water budget impact of a forest fire that partially burned a ~450 km2 subarctic Precambrian Shield basin. Water budget components were measured in a pair of catchments: one burnt and another unburnt. Burnt and unburnt areas had comparable net radiation, but thaw was deeper in burned areas. There were deeper snow packs in burns. Differences in streamflow between the catchments were within measurement uncertainty. Enhanced winter streamflow from the burned watershed was evident by icing growth at the streamflow gauge location, which was not observed in the unburned catchment. Wintertime water chemistry was also clearly elevated in dissolved organics, and organic-associated nutrients. Application of a framework to assess hydrological resilience of watersheds to wildfire reveal that watersheds with both high bedrock and open water fractions are more resilient to hydrological change after fire in the subarctic shield, and resilience decreases with increasingly climatically wet conditions. This suggests significant changes in runoff magnitude, timing and water chemistry of many Shield catchments following wildfire depend on pre-fire land cover distribution, the extent of the wildfire and climatic conditions that follow the fire.  相似文献   

8.
We used a conceptual modelling approach on two western Canadian mountainous catchments that were burned in separate wildfires in 2003 to explore the potential of using modelling approaches to generalize post‐wildfire catchment hydrology in cases where pre‐wildfire hydrologic data were present or absent. The Fishtrap Creek case study (McLure fire, British Columbia) had a single gauged catchment with both pre‐fire and post‐fire data, whereas the Lost Creek case study (Lost Ck. fire, Alberta) had several instrumented burned and reference catchments providing streamflows and climate data only for the post‐wildfire period. Wildfire impacts on catchment hydrology were assessed by comparing pre‐wildfire and post‐wildfire model calibrated parameter sets for Fishtrap Creek (Fishtrap Ck.) and the calibrated parameters of two burned (South York Ck. and Lynx Ck.) and two unburned (Star Ck. and North York Ck.) catchments for Lost Ck. Model predicted streamflows for burned catchments were compared with unburned catchments (pre‐fire in the case of Fishtrap Ck. and unburned in the case of the Lost Ck.). Similarly, model predicted streamflows from unburned catchments were compared with burned catchments (post‐fire in the case of Fishtrap Ck. and burned in the case of the Lost Ck.). For Fishtrap Ck., different model parameters and streamflow behaviour were observed for pre‐wildfire and post‐wildfire conditions. However, the burned and unburned model results from the Lost Ck. wildfire did not show differing streamflow responses to the wildfire. We found that this hydrological modelling approach is suitable where pre‐wildfire and post‐wildfire data are available but may provide limited additional insights where pre‐disturbance hydrologic data are unavailable. This may in part be because the conceptual modelling approach does not represent the physical catchment processes, whereas a physically based model may still provide insights into catchment hydrological response in these situations. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

9.
Comparison of the responses of three drainage basins burned by the Dome fire of 1996 in New Mexico is used to identify the hillslope, channel and fire characteristics that indicate a susceptibility specifically to wildfire‐related debris flow. Summer thunderstorms generated three distinct erosive responses from each of three basins. The Capulin Canyon basin showed widespread erosive sheetwash and rilling from hillslopes, and severe flooding occurred in the channel; the North Tributary basin exhibited extensive erosion of the mineral soil to a depth of 5 cm and downslope movement of up to boulder‐sized material, and at least one debris flow occurred in the channel; negligible surface runoff was observed in the South Tributary basin. The negligible surface runoff observed in the South Tributary basin is attributed to the limited extent and severity of the fire in that basin. The factors that best distinguish between debris‐flow producing and flood‐producing drainages are drainage basin morphology and lithology. A rugged drainage basin morphology, an average 12 per cent channel gradient, and steep, rough hillslopes coupled with colluvium and soil weathered from volcaniclastic and volcanic rocks promoted the generation of debris flows. A less rugged basin morphology, an average gradient of 5 per cent, and long, smooth slopes mantled with pumice promoted flooding. Flood and debris‐flow responses were produced without the presence of water‐repellent soils. The continuity and severity of the burn mosaic, the condition of the riparian vegetation, the condition of the fibrous root mat, accumulations of dry ravel and colluvial material in the channel and on hillslopes, and past debris‐flow activity, appeared to have little bearing on the distinctive responses of the basins. Published in 2000 by John Wiley & Sons, Ltd.  相似文献   

10.
A wildfire in May 1996 burned 4690 hectares in two watersheds forested by ponderosa pine and Douglas fir in a steep, mountainous landscape with a summer, convective thunderstorm precipitation regime. The wildfire lowered the erosion threshold in the watersheds, and consequently amplified the subsequent erosional response to shorter time interval episodic rainfall and created both erosional and depositional features in a complex pattern throughout the watersheds. The initial response during the first four years was an increase in runoff and erosion rates followed by decreases toward pre‐fire rates. The maximum unit‐area peak discharge was 24 m3 s?1 km?2 for a rainstorm in 1996 with a rain intensity of 90 mm h?1. Recovery to pre‐fire conditions seems to have occurred by 2000 because for a maximum 30‐min rainfall intensity of 50 mm h?1, the unit‐area peak discharge in 1997 was 6.6 m3 s?1 km?2, while in 2000 a similar intensity produced only 0.11 m3 s?1 km?2. Rill erosion accounted for 6 per cent, interrill erosion for 14 per cent, and drainage erosion for 80 per cent of the initial erosion in 1996. This represents about a 200‐fold increase in erosion rates on hillslopes which had a recovery or relaxation time of about three years. About 67 per cent of the initially eroded sediment is still stored in the watersheds after four years with an estimated residence time greater than 300 years. This residence time is much greater than the fire recurrence interval so erosional and depositional features may become legacies from the wildfire and may affect landscape evolution by acting as a new set of initial conditions for subsequent wildfire and flood sequences. Published in 2001 by John Wiley & Sons, Ltd.  相似文献   

11.
Infrequent, high‐magnitude events cause a disproportionate amount of sediment transport on steep hillslopes, but few quantitative data are available that capture these processes. Here we study the influence of wildfire and hillslope aspect on soil erosion in Fourmile Canyon, Colorado. This region experienced the Fourmile Fire of 2010, strong summer convective storms in 2011 and 2012, and extreme flooding in September 2013. We sampled soils shortly after these events and use fallout radionuclides to trace erosion on polar‐ and equatorial‐facing burned slopes and on a polar‐facing unburned slope. Because these radionuclides are concentrated in the upper decimeter of soil, soil inventories are sensitive to erosion by surface runoff. The polar‐facing burned slope had significantly lower cesium‐137 (137Cs) and lead‐210 (210Pb) inventories (p < 0.05) than either the polar‐facing unburned slope or equatorial‐facing burned slope. Local slope magnitude does not appear to control the erosional response to wildfire, as relatively gently sloping (~20%) polar‐facing positions were severely eroded in the most intensively burned area. Field evidence and soil profile analyses indicate up to 4 cm of local soil erosion on the polar‐facing burned slope, but radionuclide mass balance indicates that much of this was trapped nearby. Using a 137Cs‐based erosion model, we find that the burned polar‐facing slope had a net mean sediment loss of 2 mm (~1 kg m?2) over a one to three year period, which is one to two orders of magnitude higher than longer‐term erosion rates reported for this region. In this part of the Colorado Front Range, strong hillslope asymmetry controls soil moisture and vegetation; polar‐facing slopes support significantly denser pine and fir stands, which fuels more intense wildfires. We conclude that polar‐facing slopes experience the most severe surface erosion following wildfires in this region, indicating that landscape‐scale aridity can control the geomorphic response of hillslopes to wildfires. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

12.
Few investigations link post‐fire changes to sediment sources and erosion processes with sediment yield response at the catchment scale. This linkage is essential if downstream impacts on sediment transport after fire are to be understood in the context of fire effects across different forest environments. In this study, we quantify changing source contributions to fine sediment (<63 µm) exported from a eucalypt forest catchment (136 ha) burnt by wildfire. The study catchment is one of a pair of research catchments located in the East Kiewa River valley in southeastern Australia that have been the subject of a research program investigating wildfire effects on runoff, erosion, and catchment sediment/nutrient exports. This previous research provided the opportunity to couple insights gained from a range of measurement techniques with the application of fallout radionuclides 137Cs and 210Pbex to trace sediment sources. It was found that hillslope surface erosion dominated exports throughout the 3·5‐year post‐fire measurement period. During this time there was a pronounced decline in the proportional surface contribution from close to 100% in the first six months to 58% in the fourth year after fire. Over the study period, hillslope surface sources accounted for 93% of the fine sediment yield from the burnt catchment. The largest decline in the hillslope contribution occurred between the first and second years after fire, which corresponded with the previously reported large decline in sediment yield, breakdown of water repellency in burnt soils, substantial reduction in hillslope erodibility, and rapid surface vegetation recovery. Coupling the information on sediment sources with hillslope process measurements indicated that only a small proportion of slopes contributed sediment to the catchment outlet, with material derived from near‐channel areas dominating the post‐fire catchment sediment yield response. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

13.
The High Park Fire burned ~35 300 ha of the Colorado Front Range during June and July 2012. In the areas of most severe burn, all trees were killed and the litter and duff layers of soil were completely removed. Post‐fire erosion caused channel heads to develop well upslope from pre‐fire locations. The locations of 50 channel heads in two burned catchments were documented and the range of drainage areas contributing to these channel heads to drainage areas of unburned channel heads in the region measured previously were compared. Mean drainage area above channel heads in the burned zone decreased by more than two‐orders of magnitude relative to unburned sites. Drainage area above channel heads between the two burned catchments does not differ significantly with respect to slope, likely as a result of differences in surface roughness between the two sites following the fire. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

14.
The response time (lag time) between rainfall input and run‐off output in headwater catchments is a key parameter for flood prediction. Lag times are expected to be controlled by run‐off processes, both on hillslopes and in channels. To demonstrate these effects on peak lag times within a 4.5‐km2 catchment, we measured stream water levels at up to 16 channel locations at 1‐min intervals and compared the lag times with topographic indices describing the length and gradient of the hillslope and channel flow path. We captured storm events with a total precipitation of 38–198 mm and maximum hourly precipitation intensity of 9–90 mm/hr. There were positive relationships between lag time and flow path length as well as the ratio of the flow path length and the square root of the gradient of channels for the most intense storms, demonstrating that channel flow paths generally defined the variation in lag times. Topographic analysis showed that hillslope flow path lengths were similar among locations, whereas channel flow path length increased almost one order of magnitude with a 100‐fold increase in catchment area. Thus, the relative importance of hillslope flow path decreased with increasing catchment area. Our results indicate that the variation in lag times is small when hillslopes are sufficiently wet; thus, catchment‐scale variation in lag times can be explained almost entirely by channel processes. Detailed topographic channel information can improve prediction of flood peak timing, whereas hillslopes can be treated as homogeneous during large flood events.  相似文献   

15.
Several studies revealed that peak discharges (Q) observed in a nested drainage network following a runoff-generating rainfall event exhibit power law scaling with respect to drainage area (A) as Q(A) = αAθ. However, multiple aspects of how rainfall-runoff process controls the value of the intercept (α) and the scaling exponent (θ) are not fully understood. We use the rainfall-runoff model CUENCAS and apply it to three different river basins in Iowa to investigate how the interplay among rainfall intensity, duration, hillslope overland flow velocity, channel flow velocity, and the drainage network structure affects these parameters. We show that, for a given catchment: (1) rainfall duration and hillslope overland flow velocity play a dominant role in controlling θ, followed by channel flow velocity and rainfall intensity; (2) α is systematically controlled by the interplay among rainfall intensity, duration, hillslope overland flow velocity, and channel flow velocity, which highlights that it is the combined effect of these factors that controls the exact values of α and θ; and (3) a scale break occurs when runoff generated on hillslopes runs off into the drainage network very rapidly and the scale at which the break happens is determined by the interplay among rainfall duration, hillslope overland flow velocity, and channel flow velocity.  相似文献   

16.
There is a need for more isotopic tracer studies at the mesoscale to extend our understanding of catchment transit times and their associated controls beyond smaller experimental sites (typically < 10 km2). This paper, therefore, examines the isotope hydrology of six mesoscale (101–102 km2) sub‐catchments of the 2000 km2 basin of the River Dee in northern Scotland. All the catchments were upland in character (mean altitude > 400 m) with similar suites of soil coverage (predominantly regosols, gleys, peats and podzols), although the relative distribution varied, as did the presence of other landscape features such as aquifers in Quaternary drifts and lakes. Input–output relationships of δ18O in precipitation and runoff revealed contrasting responses and differential damping which were broadly consistent with catchment characteristics. The mean transit times (MTTs) were estimated using a convolution integral with a Gamma distribution as the transfer function. These varied from 528 days in the most responsive catchments to > 800 days in catchments where the tracer signature was most damped. Shorter MTTs were found in sub‐catchments with a higher percentage cover of responsive soils (i.e. regosols, gleys and peats), whilst sub‐catchments with longest MTTs had a higher coverage of free‐draining podzolic and alluvial soils, as well as significant amount of stored water either in fluvio‐glacial aquifers or large lakes. The MTT of all six catchments had the same order of magnitude; this contrasts with studies in the Scottish Highlands with smaller (<10 km2) catchments where MTT has been shown to vary between 60 and 1200 days. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

17.
The combined use of water erosion models and geographic information systems has facilitated soil loss estimation at the watershed scale. Tools such as the Geo‐spatial interface for the Water Erosion Prediction Project (GeoWEPP) model provide a convenient spatially distributed soil loss estimate but require discretization to identify hillslopes and channels. In GeoWEPP, the TOpographic PArameteriZation (TOPAZ) model is used as an automated procedure to extract a watershed boundary, hillslopes and channels from a digital elevation model (DEM). Previous studies in small watersheds have shown that the size of the hillslopes and the channel distribution affect the model estimates, but in large watersheds, the effects on the soil loss estimates have yet to be tested. Therefore, the objective of this study was to evaluate the effect of discretization on the hillslope sediment yield estimates using GeoWEPP in two large watersheds (>10 km2). The watersheds were selected and discretized varying the TOPAZ parameters [critical source area (CSA) and minimum source channel length (MSCL)] in a 30‐m resolution digital elevation model. The drainage networks built with TOPAZ were compared with each other using the drainage density index. The results showed that the discretization affected hillslope sediment yield estimates and their spatial distribution more than the total runoff. The drainage density index and the hillslope sediment yield were proportional but inversely related; thus, soil loss estimates were highly affected by the spatial discretization. As a result of this analysis, a method to choose the CSA and MSCL values that generates the greatest fraction of hillslopes having profile lengths less than 200 m was developed. This slope length condition is particularly crucial when using the WEPP and GeoWEPP models, in order for them to produce realistic estimates of sheet and rill erosion. Finally, and as a result of this analysis, a more reliable method was developed for selecting the TOPAZ channel network parameters (CSA and MSCL). Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

18.
After wildfire, hillslope and channel erosion produce large amounts of sediment and can contribute significantly to long-term erosion rates. However, pre-erosion high-resolution topographic data (e.g. lidar) is often not available and determining specific contributions from post-fire hillslope and channel erosion is challenging. The impact of post-fire erosion on landscape evolution is demonstrated with Structure from Motion (SfM) Multi-View Stereo (MVS) photogrammetry in a 1 km2 Idaho Batholith catchment burned in the 2016 Pioneer Fire. We use SfM-MVS to quantify post-fire erosion without detailed pre-erosion topography and hillslope transects to improve estimates of rill erosion at adequate spatial scales. Widespread rilling and channel erosion produced a runoff-generated debris-flow following modest precipitation in October 2016. We implemented unmanned aerial vehicle (UAV)-based SfM-MVS to derive a 5 cm resolution digital elevation model (DEM) of the channel scoured by debris-flow. In the absence of cm-resolution pre-erosion topography, a synthetic surface was defined by the debris-flow scour's geomorphic signature and we used a DEM of Difference (DoD) to map and quantify channel erosion. We found 3467 ± 422 m3 was eroded by debris-flow scour. Rill dimensions along hillslope transects and Monte Carlo simulation show rilling eroded ~1100 m3 of sediment and define a volume uncertainty of 29%. The total eroded volume (4600 ± 740 m3) we measured in our study catchment is partitioned into 75% channel erosion and 25% rill erosion, reinforcing the importance of catchment size on erosion process-dominance. The deposit volume from the 2016 event was 5700 ± 1140 m3, indicating ~60% contribution from post-fire channel erosion. Dating of charcoal fragments preserved in stratigraphy at the catchment outlet, and reconstructions of prior deposit volumes provide a record of Holocene fire-related debris-flows at this site; results suggest that episodic wildfire-driven erosion (~6 mm/year) dominate millennial-scale erosion (~5 mm/Ka) at this site. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.  相似文献   

19.
In hydrology, the storage‐discharge relationship is a fundamental catchment property. Understanding what controls this relationship is at the core of catchment science. To date, there are no direct methods to measure water storage at catchment scales (101–103 km2). In this study, we use direct measurements of terrestrial water storage dynamics by means of superconducting gravimetry in a small headwater catchment of the Regen River, Germany, to derive empirical storage‐discharge relationships in nested catchments of increasing scale. Our results show that the local storage measurements are strongly related to streamflow dynamics at larger scales (> 100 km2; correlation coefficient = 0.78–0.81), but at small scale, no such relationship exists (~ 1 km2; correlation coefficients = ?0.11). The geologic setting in the region can explain both the disconnection between local water storage and headwater runoff, and the connectivity between headwater storage and streams draining larger catchment areas. More research is required to understand what controls the form of the observed storage‐discharge relationships at the catchment scale. This study demonstrates that high‐precision gravimetry can provide new insights into the complex relationship between state and response of hydrological systems. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

20.
Attempts to reduce the number of parameters in distributed rainfall–runoff models have not yet resulted in a model that is accurate for both natural and anthropogenic hillslopes. We take on the challenge by proposing a distributed model for overland flow and channel flow based on a combination of a linear response time distribution and the hillslope geomorphologic instantaneous unit hydrograph (GIUH), which can be calculated with only a digital elevation model and a map with field boundaries and channel network as input. The spatial domain is subdivided into representative elementary hillslopes (REHs) for each of which we define geometric and flow velocity parameters and compute the GIUH. The catchment GIUH is given by the sum of all REH responses. While most distributed models only perform well on natural hillslopes, the advantage of our approach is that it can also be applied to modified hillslopes with for example a rectangular drainage network and terrace cultivation. Tests show that the REH‐GIUH approach performs better than classical routing functions (exponential and gamma). Simulations of four virtual hillslopes suggest that peak flow at the catchment outlet is directly related to drainage density. By combining the distributed flow routing model with a lumped‐parameter infiltration model, we were also able to demonstrate that terrace cultivation delays the response time and reduces peak flow in comparison to the same hillslope, but with a natural stream network. The REH‐GIUH approach is a first step in the process of coupling distributed hydrological models to erosion and water quality models at the REH (associated with agricultural management) and at the catchment scale (associated with the evaluation of the environmental impact of human activities). It furthermore provides a basis for the development of models for large catchments and urban or peri‐urban catchments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

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