Duration Of Inundation Research Articles

Freshwater wetland plants respond nonlinearly to inundation over a sustained period.

Wetland plants regularly experience physiological stresses resulting from inundation; however, plant responses to the interacting effects of water level and inundation duration are not fully understood. We conducted a mesocosm experiment on two wetland species, sawgrass (Cladium jamaicense) and muhly grass (Muhlenbergia filipes), that co-dominate many freshwater wetlands in the Florida Everglades. We tracked photosynthesis, respiration, and growth at water levels of -10 (control), 10 (shallow), and 35 cm (deep) with reference to soil surface over 6 months. The response of photosynthesis to inundation was nonlinear. Specifically, photosynthetic capacity (Amax ) declined by 25% in sawgrass and by 70% in muhly grass after 1-2 months of inundation. After 4 months, Amax of muhly grass in the deep-water treatment declined to near zero. Inundated sawgrass maintained similar leaf respiration and growth rates as the control, whereas inundated muhly grass suppressed both respiration and growth. At the end of the experiment, sawgrass had similar nonstructural carbohydrate pools in all treatments. By contrast, muhly grass in the deep-water treatment had largely depleted sugar reserves but maintained a similar starch pool as the control, which is critical for post-stress recovery. Overall, the two species exhibited nonlinear and contrasting patterns of carbon uptake and use under inundation stress, which ultimately defines their strategies of surviving regularly flooded habitats. The results suggest that a future scenario with more intensive inundation, due to the water management and climate change, may weaken the dominance of muhly grass in many freshwater wetlands of the Everglades.

Nutrient Budgets Calculated in Floodwaters Using a Whole‐Ecosystem Reservoir Creation and Flooding Experiment

AbstractFlooding in forested areas can release nutrients via organic matter flushing and organic matter decomposition and contribute to nutrient loading in aquatic ecosystems. Organic matter content may set an upper limit for nutrient release during flooding, but variation in timing, depth, duration of inundation, and site organic matter substrate inhibit comparison across sites and events. We used data collected during a whole‐ecosystem flooding experiment conducted at the IISD‐Experimental Lakes Area (ELA) in northwestern Ontario to examine the relationship between site organic matter content and nutrient release on both a short‐term (first 3 weeks) and annual scale (open‐water season). Three upland forest sites with differing amounts of organic matter stored in soil and vegetation were flooded to create experimental reservoirs. We hypothesized that the magnitude of nutrient release would be related to the organic matter content in each site. We found that nutrient concentrations increased relative to low‐nutrient water pumped into each reservoir at both scales, but there was no relationship between site organic matter content and short‐term total nitrogen (TN) and total phosphorus (TP) concentrations or annual TN and TP fluxes. Additionally, N and P release rates differed, decreasing TN:TP ratios in reservoirs and outflows relative to inflows. Nutrient concentrations increased immediately after inundation each year and continued for 5 years of repeated flooding. Predicted increases in flooding due to changing precipitation patterns and reservoir creation may cause forested areas to be a long‐term nutrient source to aquatic ecosystems. Over time, nutrient accumulation may affect water quality, shift biological communities, and influence ecosystem functioning.

Soil Characteristics and Hydromorphological Patterns Control Denitrification at the Floodplain Scale

Nitrate pollution in aquatic ecosystems is still a major problem in Germany. There is a great potential to permanently remove nitrate from aquatic systems through denitrification as a relevant ecosystem function. However, the controlling factors and the dimension of the denitrification potential are still not fully understood due to the high complexity of the process. This study presents the combined assessment of potential soil denitrification rates, physical and chemical soil parameters, and hydrological parameters from six floodplains of four large German rivers, namely the Rhine, the Elbe, the Weser, and the Main. Based on multivariate statistics, results show that the denitrification potential of soil was almost solely controlled by soil pH. The lab assays showed mean soil denitrification potentials of 6.4–11.4 mg N m−2h−1(pH < 7) and 23.0–30.5 mg N m−2h−1(pH > 7). We contend that when upscaling these estimates to annual rates of potential denitrification, the duration of average inundation should be incorporated, as this accounts for water saturation and nutrient supply − the major controlling variables for denitrification. Results provide evidence that the denitrification potential can only be fully exploited in frequently inundated floodplains. Thus, despite favorable soil conditions for denitrification, floodplains that have suffered from anthropogenic impacts, lose their importance in nitrate removal for the river system. We conclude that pH and lateral hydrological connectivity are likely to be key factors that should be considered when estimating denitrification as an ecosystem function.

Large-scale variation in wave attenuation of oyster reef living shorelines and the influence of inundation duration.

One of the paramount goals of oyster reef living shorelines is to achieve sustained and adaptive coastal protection, which requires meeting ecological (i.e., develop a self-sustaining oyster population) and engineering (i.e., provide coastal defense) targets. In a large-scale comparison along the Atlantic and Gulf coasts of the United States, the efficacy of various designs of oyster reef living shorelines at providing wave attenuation was evaluated accounting for the ecological limitations of oysters with regard to inundation duration. A critical threshold for intertidal oyster reef establishment is 50% inundation duration. Living shorelines that spent less than one-half of the time (<50%) inundated were not considered suitable habitat for oysters, however, were effective at wave attenuation (68% reduction in wave height). Reefs that experienced >50% inundation were considered suitable habitat for oysters, but wave attenuation was similar to controls (no reef; ~5% reduction in wave height). Many of the oyster reef living shoreline approaches therefore failed to optimize the ecological and engineering goals. In both inundation regimes, wave transmission decreased with an increasing freeboard (difference between reef crest elevation and water level), supporting its importance in the wave attenuation capacity of oyster reef living shorelines. However, given that the reef crest elevation (and thus freeboard) should be determined by the inundation duration requirements of oysters, research needs to be refocused on understanding the implications of other reef parameters (e.g., width) for optimizing wave attenuation. A broader understanding of the reef characteristics and seascape contexts that result in effective coastal defense by oyster reefs is needed to inform appropriate design and implementation of oyster-based living shorelines globally.

KAJIAN PENANGANAN BANJIR DENGAN SISTEM POMPA DI SUNGAI BENDUNG, KOTA PALEMBANG

Floods around the Bendung River in Palembang City have caused material and non-material losses. One of the reasons was the decreasing river capacity and backwater during the Musi River flood season, which is the Bendung River's outlet. This paper discusses the impact of adding a pump system to reduce flood impact. 1-dimensional and 2-dimensional numerical model using MIKE 11 and MIKE FLOOD were made to analyze the best measures. Various alternative scenarios were implemented in the model. Based on the modeling results, using the most optimal alternative, alternative 4 with 6 pumps of 36 m3/s and normalization of the Bendung River channel by 1 meter. The inundation area was reduced by 0.74 km2. Also, the maximum inundation height for the flood decreased by 0.6 meters, and the inundation duration was reduced by 8.5 hours. These modeling results can be a reference for managers and policymakers in managing flood events.Keywords: River channel normalization, pump system, numerical model, flood control, Bendung river

Community Trait Responses of Three Dominant Macrophytes to Variations in Flooding During 2011-2019 in a Yangtze River-Connected Floodplain Wetland (Dongting Lake, China).

In lacustrine wetlands connected to rivers, the changes in flood regimes caused by hydrological projects lead to changes in the community traits of dominant macrophytes and, consequently, influence the structure and function of wetland vegetation. However, community trait responses of macrophytes to the timing and duration of flood disturbance have been rarely quantified. In 2011–2019, we investigated plant species diversity, density, and biomass in three dominant macrophyte communities (Carex brevicuspis C.B. Clarke, Miscanthus sacchariflorus (Maxim.) Hackel, and Polygonum hydropiper L.) through monthly field surveys in Dongting Lake wetlands. Partial least squares regressions were used to analyze how the variations in hydrological regimes affected plant community traits. Apparent inter-annual fluctuations in plant community traits were detected during 2011–2019. The species richness and Shannon index of diversity of Miscanthus and Polygonum communities increased, whereas the Shannon index of diversity of Carex community decreased. Variation in flooding had a greater effect on Polygonum and Carex community traits than on Miscanthus community traits. Flooding disturbed all plant communities, especially when the duration and timing varied. Shorter inundation periods caused the biomass of Miscanthus community to decline, and that of Carex and Polygonum communities to increase. Earlier flood recession caused the species richness and Shannon index of diversity of Polygonum and Miscanthus community to increase, and those of Carex community to decrease. These findings imply that shorter inundation durations and earlier flood recession generated by the operation of the Three Gorges Dam have changed the macrophyte growth pattern.

The influence of flood frequency and duration on microcrustacean egg bank composition in dryland river floodplain sediments

Abstract Several studies of temporary floodplain wetlands suggest that flood history is important to microcrustacean egg bank composition and hatching responses. However, these studies have largely focussed on contrasts among less frequently flooded areas (areas flooded every year to areas flooded once every 10–20 years) and less is known about variation at the more frequently flooded end of the gradient (from multiple floods per year to once every 2 years). Similarly, the effects of flood duration on egg banks have not been examined in detail. Thus, this study examines spatial variation in microcrustacean hatching at higher flood frequencies and in relation to inundation duration. Surface sediment samples were collected from dry anabranches of the Macintyre River floodplain in Australia during February 2018, with a range of flood frequency from approximately four times per year to one in 2 years. Anabranches were selected randomly from predefined flood frequency classes and clustered into three different flood history groups based on flood history variables. Soil samples were collected from deep and shallow locations within anabranches, with depth assumed to be a proxy for the duration of inundation. Sediment samples were inundated in mesocosms and hatched microcrustaceans sampled over 6 weeks. Microcrustacean abundance and assemblage composition varied by sites, relative depth, and duration of inundation. There was no variation by flood history groups. Highest numbers hatched from the deeper areas of anabranches, which is assumed to reflect differences in the egg banks of deep and shallow areas due to the longer duration of inundation in deeper areas. Duration also influenced hatching response from the egg bank, with more microcrustaceans hatching per unit time in the first 2 and final 2 weeks of the 6‐week trial than the middle 2 weeks. Species richness also varied by relative depth and duration of inundation with more taxa hatching from the deeper areas of anabranches. The study highlights the critical influence of flood duration on hatching patterns of microcrustaceans from inundated sediments. Therefore, changes to flood duration have the potential to influence microcrustacean assemblages and thus further changes to trophic interactions in temporary floodplain wetlands. ​

Hydrological and geomorphic effects upstream of the Cantillana Dam along the Guadalquivir River (southern Spain)

Hydrological and geomorphological impacts upstream dams have been less frequently investigated than those occurring downstream. Geomorphological mapping, multitemporal analysis of aerial photos, topographic survey comparison of the channel bed, and archives of information concerning flood events were used in this paper to document the effects that occurred upstream of the Cantillana Dam along the lower Guadalquivir River. The results show that the construction of the dam in 1956 caused progressive siltation that reduced either the water surface width (36.5% until 2010) or the reservoir volume (70% reduction until 2012). These changes decrease from the upstream boundary of the reservoir to the dam but show an increase in correspondence with the main tributary (Rivera de Huéznar) in the middle part. The aggradational process along the reservoir reach caused a reduction in the channel cross-sectional area and its flow capacity during floods. Consequently, higher river stages are reached for the same flow discharge, thereby producing an increased frequency and duration of inundation of the alluvial terraces adjacent to the reservoir.

Flood Quantification Index Based on Inundation Indicators and Risk Scale

Flood management requires an assessment of flood levels that occur appropriately. Determining flood levels quantitatively can help control floods more efficiently. This study aims to make flood quantification based on the inundation indicators and scale of risk. The case study is in Citarik, Cilember, Cimahi, Cisangkan, and Cibeureum, located in the Citarum watershed, West Java, Indonesia. The method used is a mathematical model of flow verified by the river's physical dimensions. Four indicators were analyzed based on unsteady one-dimensional river flow and overland flow models. The four flood quantity indicators with different weights are namely percentage of inundation area (Ai), percentage of area activity on the inundation area (Aac), inundation duration (D), and inundation depth (H) which have consecutive indexes 0.3, 0.2, 0.2 and 0.3. The initial discharge was analyzed based on unit hydrograph at the upstream river cross-section of the inundation region. The study's results by verification of field observations showed that the highest peak inundation was 3.0 m in Cilember, inundation duration was a maximum of 18 hours in Citarik and Cilember, the highest inundation area was 329.23 % of the watershed area of Cilember. Results of calculations with the formulations, the highest quantity is 16.18 in Cilember flood that occurs in Melong village with a risk scale of 5. These results conclude that the Cilember flood is high-level damage so that it is a priority to be overcome.

Water balance scheme development for urban modelling

Urban flooding is a big problem for developing countries like China. The parameterization of urban water balance schemes is important to urban latent heat flux and urban land-atmosphere interaction studies. Now, various kinds of urban hydrological schemes are developed to simulate the urban water cycle; but some key physical processes about urban water balance still need to be addressed. In this paper, the urban water balance schemes are developed and coupled with the Integrated Urban land Model (IUM) to improve the urban modelling framework. The inundation depths on natural, urban road and urban roof surfaces are used as prognostic variables of water balance equations. The results indicate the values of urban latent heat flux are associated with the duration time of water inundation. After parameter calibration based on the observed inundation depths in road sites, IUM can simulate water inundation depths well compared to those of the observations. Based on mechanism study, several mitigation strategies were put forward and sensitivity analyses were implemented. The results indicate these mitigation strategies can reduce the urban inundation depth and shorten the inundation duration time.

Flood Inundation Assessment in the Low-Lying River Basin Considering Extreme Rainfall Impacts and Topographic Vulnerability

This study aims to evaluate the change in flood inundation in the Chitose River basin (CRB), a tributary of the Ishikari River, considering the extreme rainfall impacts and topographic vulnerability. The changing impacts were assessed using a large-ensemble rainfall dataset with a high resolution of 5 km (d4PDF) as input data for the rainfall–runoff–inundation (RRI) model. Additionally, the prediction of time differences between the peak discharge in the Chitose River and peak water levels at the confluence point intersecting the Ishikari River were improved compared to the previous study. Results indicate that due to climatic changes, extreme river floods are expected to increase by 21–24% in the Ishikari River basin (IRB), while flood inundation is expected to be severe and higher in the CRB, with increases of 24.5, 46.5, and 13.8% for the inundation area, inundation volume, and peak inundation depth, respectively. Flood inundation is likely to occur in the CRB downstream area with a frequency of 90–100%. Additionally, the inundation duration is expected to increase by 5–10 h here. Moreover, the short time difference (0–10 h) is predicted to increase significantly in the CRB. This study provides useful information for policymakers to mitigate flood damage in vulnerable areas.

Developing a multivariable lookup table function for estimating flood damages of rice crop in Vietnam using a secondary research approach

It is increasingly important to evaluate the economic flood damage toward agricultural crops to further improve decision-making and mitigate flood impacts in developing countries. In this study, we derive a multivariable lookup table function for estimating flood damages to rice crops based on a secondary research approach, which involves collecting and integrating fragmented secondary information sources of rice damage caused by inundation and event data observed in southern rural areas of the Ca River Basin, Central Vietnam. The derived lookup table function includes the effects of the rice growth stages on the damage caused, in addition to flooding parameters such as inundation level and inundation duration. This indicates that the rice crops are generally the most vulnerable and robust to inundation in the ripening and the reproductive stages. The yield loss in the ripening stage dramatically increases from 50% to 90% when the complete inundation lasts 5–8 days. Even after 7 days of 75% inundation, the yield hardly decreased at the reproductive stage and was reduced by almost half for 7 days of complete inundation. Four–five days of complete inundation at the ripening and vegetation stages are likely to cause almost the same damage to rice crops as that caused by 7 days of inundation at the reproductive stage. Utilization of the function to estimate rice damage in four flood events reveals that the derived multivariable function captures flood damages well and outperforms the univariable damage functions for the target area.

Amazon floodplain hydrology and implications for aquatic conservation

Abstract The amplitude, duration, frequency, and predictability of runoff and inundation of aquatic habitats are key hydrological characteristics linked to aquatic ecosystem functioning and biodiversity, but they are seldom integrated into analyses of Amazon floodplain ecology. Remote sensing approaches, measurements and modelling of floodplain hydrology provide a basis for this integration. Effective legislation to protect floodplains and other wetlands depends on operational definitions that require application of hydrological data. Extent and changes of flooded areas are linked to fish diversity and to presence and growth of flooded forests and floating plants. Dam construction reduces river system connectivity and modifies the flood pulse, with major negative implications for floodplain ecosystems adapted to and dependent on a natural flood regime. Trends and variability in climate plus deforestation are altering the Amazon's hydrological cycle, causing changes in discharge and flooded area with concomitant ecological impacts.

STOK KARBON DI ATAS PERMUKAAN TANAH PADA HUTAN MANGROVE SUNGAI AWAN KIRI KABUPATEN KETAPANG

Mangrove forests, often referred to as mangrove forests, brackish forests or tidal forests, is a transitional ecosystem between land and sea which are tropical or sub-tropical areas along the sheltered coast and river mouth. Mangrove forest is a coastal plant community dominated by several species of mangrove trees that are able to grow and develop during the tides in accordance with their tolerance to salinity, duration of inundation, substrate and beach morphology. Awan Kiri Mangrove Forest has a total area of 114 hectares including the area of Other Management Areas (APL) then seen from the density of the Mangrove Forest only has 92 hectares. This study uses a non-destructive survey method. Vegetation carbon stock calculation is carried out using vegetation biomass calculation approach. Vegetation biomass calculation based on the calculation of allometric equations. Calculation the value of stored carbon using the formula according to (SNI 7724:2011) the value of parent carbon content,amounting to 0,47. Bassed on the research that has been done, it is found that there are 185 individuals, Rhizophora spp., Bruguiera gymnorhiza, Rhizpphora apiculata, Xylocarpus gerantum and Excoecaria agallocha. The biomassa content can be known in the 3 pathways to store 242,16 tons biomassa and the total biomassa content in 1210,8 tons/ha with an everage of 403,6 tons/ha. The carbon content is 569,06 tons/ha so that it gets an average total of 186,68 tons C/ha.Keywords: Carbon Stock, Ketapang Regency, Sungai Awan Kiri in Mangrove Forests.

Local Participatory Flood Hazard Mapping’s Assessment and Coping: A Conceptual Model of Sustainability in Downstream Area of Belu Regency in the Western Timor Island, East Nusa Tenggara Province, Indonesia

This study applies interview, Focus Group Discussion (FGDs), Participatory Geographical Information Systems (pGIS), and a conceptual model of sustainability (CMS) using risk perception of local community to map flood hazard and assess the social and cultural copings to cope with river flooding in downstream areas i.e., Lasaen, Umatoos, and Fafoe villages of West Malaka Subdistrict of Belu Regency, Indonesia. The results of this study indicate that the rural-river flooding was inundated at all three villages. The cycle of flood is twenty-years per event (1939, 1959, 1975, 1999 through 2000), and from 2000 its occurrence was each year until 2012. Based on interviews and FGDs, the information of flood characteristics of Lasaen and Fafoe villages were similar, but Umatoos village was not. The single longevity of flood inundation was in Fafoe village (1 week-1 month). Whilst Lasaen and Umatoos villages were experiencing less duration of flood inundations (0-7 days to 14-21 days). Lasaen and Umatoos Villages were dealing with flood depth&amp;rsquo;s variation from the lowest depth (0-50cm) to its deepest (251-300cm). For CMS, the most invaluable coping that might be sustainable was cultural capital. Both social and cultural coping enhancements were implemented by local community. The minimum and lack of both these transformable sub-copings were still the problem in the discourse unit of sustainability. As each sub-coping would be overlapped if there has no sufficient distribution of it, utilized by the local community. The genuineness local knowledge of community in applying their social and cultural copings in sustainability is seen as a unique reference and a useful form of local wisdom which can be highlighted and adopted as an effective and/or example discourse analysis by the other rural villages in developing nations that are also still struggling and coping with flood disaster.

Flood Impacts on Dairy Farms in the Bay of Plenty Region, New Zealand

Flood damage assessments provide critical information for flood hazard mitigation under changing climate conditions. Recent efforts to improve and systemise damage assessments have focused primarily on urban environments with few examples for primary industries such as dairy. This paper explores the adverse consequences of flooding on dairy farms in the Bay of Plenty region, New Zealand. Ex-tropical Cyclone Debbie in April 2017 caused prolonged riverine and surface water flooding on over 3500 hectares of dairy farmland. The event provided an opportunity to develop and apply a participatory approach for collecting information about on-farm flood damage, and both response and recovery actions implemented by dairy farmers. Semi-structured interviews and transect walks with farmers revealed a range of direct and indirect damages to production and capital assets, influenced by duration of inundation, silt deposition and seasonality. Results highlight the need to identify on-farm and off-farm asset interdependencies of dairy farm systems to estimate long-term socio-economic consequences at farm-level. Enhancing dairy farm flood resilience in a changing climate will rely on farm-level response and recovery plans, proactively supported by emergency management agencies, farm service suppliers and support agencies.

Influence of inundation characteristics on the distribution of dryland floodplain vegetation communities

Semi-arid floodplain vegetation is an essential component of floodplain and terrestrial ecosystems due to the wide range of services provided for waterbirds, woodland birds, amphibians and mammals, together with their contribution to natural carbon sequestration. Since overbank flooding has been considered the driving factor of vegetation distribution on floodplains, sustainable water resource management requires a better understanding of the influence of inundation on vegetation distribution. We examined the relationship between the distribution of four flood-dependant vegetation communities and associated long term inundation metrics on the upper Darling River floodplain using electivity analysis and a generalised additive model (GAM) by generating a total of 10,478 individual inundation maps with a high spatial resolution over a period of 29 years. Our results show that the four dominant vegetation communities are situated differently in relation to inundation attributes. The inundation metrics better explained the variation in the distribution of River Red Gum than those of Black box, Coolabah and Lignum communities. We found that the floodplain forests and woodlands in the upper Darling can survive longer periods of drought and shorter inundation duration than previously reported. The results provide practical information for ecosystem management by offering a means of predicting changes in vegetation distribution in relation to alteration in flow regime resulting from water planning arrangements or climate change.

Soil anti-scourability enhanced by herbaceous species roots in a reservoir water level fluctuation zone

Revegetation is one of the successful approaches to soil consolidation and streambank protection in reservoir water level fluctuation zones (WLFZs). However, little research has been conducted to explore the impact of herbaceous species roots on soil anti-scourability during different growth stages and under different degrees of inundation in this zone. This study sampled two typical grasslands (Hemarthria compressa grassland and Xanthium sibiricum grassland) at two elevations (172 and 165 m a.s.l.) in the water level fluctuation zone (WLFZ) in the Three Gorges Reservoir (TGR) of China to quantify the changes in soil and root properties and their effects on soil anti-scourability. A simulated scouring experiment was conducted to test the soil anti-scourability in April and August of 2018. The results showed that the discrepancy in inundation duration and predominant herbaceous species was associated with a difference in root biomass between the two grasslands. The root weight density (RWD) values in the topsoil (0-10 cm) ranged from 7.31 to 13 mg cm−3 for the Hemarthria compressa grassland, while smaller values ranging from 0.48 to 8.61 mg cm−3 were observed for the Xanthium sibiricum grassland. In addition, the root biomass of the two herbs was significantly greater at 172 m a.s.l. than that at 165 m a.s.l. in the early recovery growth period (April). Both herbs can effectively improve the soil properties; the organic matter contents of the grasslands were 128.06% to 191.99% higher than that in the bare land (CK), while the increase in the water-stable aggregate ranged from 8.21% to 18.56%. Similarly, the topsoil anti-scourability indices in both the herbaceous grasslands were larger than those in the CK. The correlation coefficients between the root length density (RLD), root surface area density (RSAD) and root volume density (RVD) of fine roots and the soil anti-scourability index were 0.501, 0.776 and 0.936, respectively. Moreover, the change in the soil anti-scourability index was more sensitive to alternations in the RLD with diameters less than 0.5 mm. Overall, the present study showed that the perennial herbaceous (H. compressa) has great potential as a countermeasure to reduce or mitigate the impact of erosion in the WLFZ of the Three Gorges Reservoir.

Salvaging and replanting 300 mangrove trees and saplings in the arid Arabian Gulf

Construction works along a causeway at Mubarraz Island near Abu Dhabi, United Arab Emirates, in the Arabian Gulf necessitated the salvaging and replanting of 300 mangroves (Avicennia marina). Mangroves were excavated manually by shovel (smaller trees and saplings) or mechanically using a backhoe excavator (larger trees), transported with the root ball wrapped in burlap and replanted in a newly created tidal channel. Relocated mangroves were exposed to two different watering regimes and two tidal inundation levels, and were monitored for survival, plant height and leaf health (percentage of green leaves) at 0 and 1 weeks, and then at 3, 7 and 12.5 months. Tree mortality was high in the first week (24%) in mid-summer, with further losses (43%) during the next 3 months. After 12.5 months, 31% of the transplanted trees had survived. There was a significant effect of the duration of tidal inundation on survival and leaf health (higher survival in shallow than deeper plots). There were no significant effects of initial tree height or freshwater treatment on survival or plant performance. These results demonstrate that salvaging of larger mangroves is technically feasible, potentially providing faster ecosystem services (e.g. shoreline protection, source of new propagules) than newly planted seedlings in arid regions where growth is extremely slow.

Future regulated flows of the Colorado River in Grand Canyon foretell decreased areal extent of sediment and increases in riparian vegetation

Sediment transfer, or connectivity, by aeolian processes between channel-proximal and upland deposits in river valleys is important for the maintenance of river corridor biophysical characteristics. In regulated river systems, dams control the magnitude and duration of discharge. Alterations to the flow regime driven by dams that increase the inundation duration of sediment, or which drive the encroachment of vegetation into areas formerly composed of labile sediment and result in channel narrowing, may reduce sediment transfer from near-channel deposits to uplands via aeolian processes. Employing spatial methods developed by Kasprak et al (2018 Prog. Phys. Geogr.), here we use data describing the areal extent of bare (i.e. subaerially exposed and non-vegetated) sediment along 168 km of the Colorado River downstream from Glen Canyon Dam in Grand Canyon, USA, in conjunction with inundation extent modeling to forecast how future flows of this highly regulated river will drive changes in the areal extent of sediment available for aeolian transport. We also compare modern bare sediment area to that which presumably would have existed under pre-dam hydrographs. Over the next two decades, the planned flow regime from Glen Canyon Dam will result in slight decreases in bare sediment area (−1%) on an annual scale. This is in contrast to pre-dam years, when unregulated low flows led to marked increases in bare sediment area as compared to the current discharge regime. Our findings also indicate that ∼75% of bare sediment in the study reach is inundated continuously at present, owing to increased baseflows in the post-dam flow regime; consequently, any reductions in flows below modern-day low discharges have the potential to expose large areas of bare sediment. We use vegetation modeling to quantify areas susceptible to vegetation encroachment under future flows, finding that 80% of bare sediment area is suitable for colonization by invasive tamarisk under the current flow regime. Our findings imply that the Colorado River in Grand Canyon, a system marked by widespread erosion of sediment resources and encroachment of riparian vegetation in the post-dam period, is likely to continue to see decreasing bare sediment extent over the coming decades in the absence of direct intervention through flow regime modification or widespread vegetation removal.