Typical Floodplain Research Articles

Interactions between fire and flooding in a southern African floodplain system (Okavango Delta, Botswana)

A series of 98 satellite images was analysed to reconstruct the fire and flood history of a floodplain system in southern Africa (Okavango Delta, Botswana). The data was used to investigate interactions between fire and flooding, and to determine the relevance of rainfall and flood-events for fire occurrences on floodplains and on drylands. The aims of the study are (1) to analyse and compare the fire frequency on floodplains and on adjacent drylands, (2) to investigate the influence of rainfall and flooding on the fire occurrence and (3) to determine correlations between fire frequency and flood frequency. The analyses show higher fire frequencies on floodplains than on drylands because of higher biomass production and fuel loads. The fire occurrence on drylands shows a correlation with annual rainfall events, while the fire frequency on floodplains is in principle determined by the flood frequency. Between floodplain types, clear differences in the susceptibility to fire where shown by analysing flood frequency vs. fire frequency. Here, the highest potential to burn was found for floodplains that get flooded about every second year. By calculating mean fire return intervals, the potential to burn could be specified for the different floodplain types.

Assessing floodplain condition

Protocols being developed to assess wetland condition are based on assumptions and procedures that cannot be readily applied to one of the most ecologically significant types of wetland in Australia – riverine floodplains. This is a serious omission in wetland assessment as riverine floodplains are extensive, accounting for 5% of the area of New South Wales. However assessing floodplains is undoubtedly a challenge, as floodplains have characteristics that distinguish them from other inland wetlands. Four such characteristics are their large size, their diversity, their complexity and the distance between habitat elements for dependent floodplain fauna. Progress towards a floodplain assessment protocol could accelerate if the following were in place: a conceptual framework with understanding of floodplain functioning, for all types of floodplains; a geomorphic classification of floodplains tailored towards ecological users; capacity and skills to manage floodplains as entities.

Relationships between productivity and nutrient circulation within two contrasting southeastern U.S. floodplain forests

Patterns of nutrient circulation were examined to provide insight into the controlling mechanisms behind differences in aboveground net primary production (ANPP) among floodplain forest types. Geochemical and biogeochemical contrasts typical of many riverine forests are exemplified by the floodplains of the Satilla and Altamaha Rivers, blackwater and redwater river systems, respectively, located in Georgia, USA. Since floodplains possess high microtopographic variation, measurement plots were established to cover a range of topographic positions across both floodplains. Given the low nutrient and sediment loads that are characteristic of blackwater rivers, we hypothesized that the Satilla floodplain (SAT) would have lower ANPP and more efficient nutrient use efficiency (NUE). While both floodplains had similar amounts of litterfall production, the Altamaha floodplain (ALT) had greater stem production and, therefore, higher rates of ANPP. On the SAT, the relationship between litterfall mass and litterfall phosphorus (P) content, high P NUE, and high P resorption proficiency suggested that P was the primary limiting nutrient. While (N) circulation patterns were similar for the floodplains, ALT floodplain litterfall N/P ratios and N NUE suggested that N limitation was paramount there. Patterns of base cation circulation on the SAT indicated low calcium and potassium circulation and higher NUE of these elements compared to the ALT. In contrast, the Altamaha floodplain displayed low magnesium (Mg) circulation and high Mg NUE. Differences in P circulation and P NUE appeared to have the largest influence on ANPP between these eutrophic (ALT) and oligotrophic (SAT) floodplain forests. Furthermore, differences in base cation circulation and NUE suggested that biogeochemical distinctions between these two floodplain types could be made on the basis of base cation availability.

Response of fishes to floodplain connectivity during and following a 500-year flood event in the unimpounded upper Mississippi River

We examined data collected on fish assemblage structure among three differing floodplain types (broad, moderate, and narrow) during the 1993 flood in the unimpounded reach of the upper Mississippi River. This 500 year flood event provided a unique opportunity to investigate fish-floodplain function because the main river channel is otherwise typically disjunct from approximately 82% of its floodplain by an extensive levee system. Fishes were sampled during three separate periods, and 42 species of adult and young-of-the-year (YOY) fishes were captured. Analysis of similarity (ANOSIM) revealed a significant and distinguishable difference between both adult and YOY assemblage structure among the three floodplain types. Analysis of variance revealed that Secchi transparency, turbidity, water velocity, and dissolved oxygen were significantly different among the floodplain types. However, only depth of gear deployment and Secchi transparency were significantly correlated with adult assemblage structure. None of these variables were significantly correlated with YOY assemblage structure. The numerically abundant families (adult and YOY catches combined) on the floodplain included Centrarchidae, Ictularidae, and Cyprinidae. Both native and non-native fishes were captured on the floodplain, and several of the numerically abundant species that were captured on the floodplain peaked in catch-per-unit-effort 1–3 years after the 1993 flood event. This suggests that some species may have used flooded terrestrial habitat for spawning, feeding, or both. The findings from our study provide much needed insight into fish-floodplain function in a temperate, channelized river system and suggest that lateral connectivity of the main river channel to less degraded reaches of its floodplain should become a management priority not only to maintain faunal biodiversity but also potentially reduce the impacts of non-native species in large river systems.

Wood growth patterns of Macrolobium acaciifolium (Benth.) Benth. (Fabaceae) in Amazonian black-water and white-water floodplain forests

Macrolobium acaciifolium (Benth.) Benth. (Fabaceae) is a dominant legume tree species occurring at low elevations of nutrient-poor black-water (igapó) and nutrient-rich white-water floodplain forests (várzea) of Amazonia. As a consequence of the annual long-term flooding this species forms distinct annual tree rings allowing dendrochronological analyses. From both floodplain types in Central Amazonia we sampled cores from 20 large canopy trees growing at identical elevations with a flood-height up to 7 m. We determined tree age, wood density (WD) and mean radial increment (MRI) and synchronized ring-width patterns of single trees to construct tree-ring chronologies for every study site. Maximum tree age found in the igapó was more than 500 years, contrary to the várzea with ages not older than 200 years. MRI and WD were significantly lower in the igapó (MRI=1.52+/-0.38 mm year(-1), WD=0.39+/-0.05 g cm(-3)) than in the várzea (MRI=2.66+/-0.67 mm year(-1), WD=0.45+/-0.03 g cm(-3)). In both floodplain forests we developed tree-ring chronologies comprising the period 1857-2003 (n=7 trees) in the várzea and 1606-2003 (n=13 trees) in the igapó. The ring-width in both floodplain forests was significantly correlated with the length of the terrestrial phase (vegetation period) derived from the daily recorded water level in the port of Manaus since 1903. In both chronologies we found increased wood growth during El Niño events causing negative precipitation anomalies and a lower water discharge in Amazonian rivers, which leads to an extension of the terrestrial phase. The climate signal of La Niña was not evident in the dendroclimatic proxies.

Microsite Influences on Productivity and Nutrient Circulation Within Two Southeastern Floodplain Forests

At broad spatial scales, floodplain forests of the southeastern USA are often perceived as either nutrient poor or nutrient rich. Perceived differences in nutrient availabilities between oligotrophic blackwater and eutrophic redwater floodplain forests suggest rates of aboveground net primary production (ANPP) are lower on the former. However, for these floodplain types, microsite variation may influence relationships between nutrient circulation and ANPP to a greater extent than landscape position and geomorphology of their associated watershed. Therefore, our objectives were to compare ANPP, nutrient circulation through litterfall and decomposition, and the microbial biomass among microsites that differed in terms of soils and hydrology within two riverine floodplain forests. The two floodplains used in this study were located along the Satilla River, a Coastal Plain blackwater system, and the Altamaha River, a Piedmont redwater system, both of which are located in southeastern Georgia. Microsite influences on ANPP were not significantly different during 1999 and 2000 for the Satilla (SAT) and Altamaha (ALT) floodplains. Litterfall production and patterns of P and Ca circulation on the SAT floodplain were significantly lower for the driest microsite type during both years. Microbial biomass N and P were also lowest for the driest microsite, especially in 2000. Overall, microsites on the SAT displayed greater variation in P and Ca cycling than did those of the ALT. Litterfall production, nutrient circulation in litterfall and decomposition, and the microbial biomass were similar among microsites of the ALT floodplain during both years. These findings suggest that spatial variability in nutrient cycling may be greater for oligotrophic floodplain forests.

Growth and population structure of timber species in Peruvian Amazon flood plains

This study provides specific ecological information on growth and population structure of important timber tree species of the Peruvian Amazon flood plains: Guatteria sp., Terminalia oblonga, Hura crepitans, Guarea macrophylla, Maquira coriacea, Virola elongata, Virola pavonis, and Minquartia guianensis. Furthermore, methods that can be applied to study population structure and growth of trees in natural forests are developed upon. The study is based on data collected over a period of 8 years from permanent sample plots covering a total of 18.6 ha in three flood plain forest types at the lower Río Ucayali. The population structure of the eight species varied considerably with maximum diameters at breast height ranging from 31 to 140 cm. For M. coriacea stem densities and basal areas were as high as 159 ha −1 and 3.4 m 2/ha, respectively, but for most other species, stem densities and basal areas were much lower. Seedling densities of the eight species ranged from 1 to 42,002 ha −1 with a mortality of 27–100% per year and for some species a significant relationship was found between mortality and duration of the flooding period. Diameter increments were analyzed using a simple diameter class approach as well as a more sophisticated single-tree growth model, for which a variety of competition indices were screened. Based on the statistical performance and practicability of the indices it appeared that the most successful measure of competition was the local basal area of trees with diameters exceeding that of the individual in question.

Restoration ecology meets carabidology: effects of floodplain restitution on ground beetles (Coleoptera, Carabidae)

The effects of different restoration activities on floodplain-inhabiting ground beetles were studied at a lowland river in northwestern Germany. In the 6-km2 project area the bank reinforcement was stopped, the dikes that bordered the river on both sides were removed and two oxbows (disconnected parts of the main stream course) were reconnected to the river. We investigated the banks at two sites at the main river, at the two reconnected oxbows and at two unconnected oxbows as reference sites. To analyse the effects of the removal of the dikes we chose three floodplain sites in front and two reference sites behind the new dike. As a consequence of the lack of bank reinforcement and the reconnection of the oxbows, the area of open river banks, a rare bank structure at rivers in northwestern Germany, increased by a factor of 4.6 during the 4 years of investigation. Numerous stenotopic ground beetle species colonized the newly developed habitats at the main river and at the reconnected oxbows quickly, during several weeks or months, and established new populations as indicated by newly hatched individuals. The removal of the dikes should lead to a rewetting of the floodplain area that is incorporated in the flood dynamics, an important aspect of the development of typical floodplain habitats such as wet meadows, reeds and alluvial forests, while reference sites on the other side of the removed dike remained uninfluenced. Four years after the removal of the dikes no species turnover at the sites with a potentially changed water regime was recorded that indicated a shift of the carabid assemblages towards hygrophilous species. One reason could be the low frequency of inundations and their short duration during the investigation period. The flood dynamics could be sustained by the elevation and enlargement of the river bed, and periodic floods are the key factor for a development of floodplain habitats.

BIOGEOCHEMICAL AND METABOLIC RESPONSES TO THE FLOOD PULSE IN A SEMIARID FLOODPLAIN

Flood pulse inundation of riparian forests alters rates of nutrient retention and organic matter processing in the aquatic ecosystems formed in the forest interior. Along the Middle Rio Grande (New Mexico, USA), impoundment and levee construction have created riparian forests that differ in their inter-flood intervals (IFIs) because some flood- plains are still regularly inundated by the flood pulse (i.e., connected), while other flood- plains remain isolated from flooding (i.e., disconnected). This research investigates how ecosystem responses to the flood pulse relate to forest IFI by quantifying nutrient and organic matter dynamics in the Rio Grande floodplain during three years of experimental flooding of the disconnected floodplain and during a single year of natural flooding of the connected floodplain. Surface and subsurface conditions in paired sites (control, flood) established in the two floodplain types were monitored to address metabolic and biogeochemical responses. Compared to dry controls, rates of respiration in the flooded sites increased by up to three orders of magnitude during the flood pulse. In the disconnected forest, month-long experimental floods produced widespread anoxia of four-week duration during each of the three years of flooding. In contrast, water in the connected floodplain remained well ox- ygenated (3-8 ppm). Material budgets for experimental floods showed the disconnected floodplain to be a sink for inorganic nitrogen and suspended solids, but a potential source of dissolved organic carbon (DOC). Compared to the main stem of the Rio Grande, flood- water on the connected floodplain contained less nitrate, but comparable concentrations of DOC, phosphate-phosphorus, and ammonium-nitrogen. Results suggest that floodplain IFI drives metabolic and biogeochemical responses dur- ing the flood pulse. Impoundment and fragmentation have altered floodplains from a mosaic of patches with variable IFI to a bimodal distribution. Relatively predictable flooding occurs in the connected forest, while inundation of the disconnected forest occurs only as the result of managed application of water. In semiarid floodplains, water is scarce except during the flood pulse. Ecosystem responses to the flood pulse are related to the IFI and other measures of flooding history that help describe spatial variation in ecosystem function.

Effects of dykes on plant species composition in a large lowland river floodplain

AbstractThe effects of floodplain fragmentation by dykes on grassland vegetation were evaluated through field studies along the Middle Elbe River (federal states Saxony‐Anhalt and Brandenburg, Germany). Plant species composition was examined in 206 sites between 1996 and 1998 in the entire floodplain, which can be divided into the floodplain types ‘recent floodplain’, ‘older floodplain’ (which is separated from the recent one by dykes) and the ‘margin of the floodplain’ (which is the part of the older floodplain that forms the boundary and is furthest from the river). Dynamics in hydrology were examined weekly between November 1996 and February 1999 with the help of 40 water level wells which were installed near the studied sites. The hydrological parameters ‘average water level’, ‘average groundwater level’, ‘flooding duration’, ‘flooding depth higher 50 cm above soil surface’ and ‘standard deviation of the water level line’ were calculated to characterize the considered floodplain types and to relate species composition to hydrology. Furthermore several parameters of current management of the vegetation were recorded to evaluate the importance of land use versus hydrology for floodplain grasslands.Detrended and canonical correspondence analysis (DCA, CCA) were used to identify major environmental gradients governing the vegetation and to determine if there is a relationship between the different locations within the floodplain, variation in species composition, and gradients of measured environmental variables.The results indicate that the vegetation is closely related to a combination of water level fluctuations, which are different among the floodplain types, and soil moisture, while type and intensity of current management are not important in this context.The results of contingency tables underline the significance of dykes for the occurrence and absence of individual species among the floodplain types. The observed patterns can also be explained by the different hydrological properties of the recent and older floodplain as the results of logistic regression reveal. Furthermore, disturbance and dispersal processes and their alteration by dykes have to be taken into account to explain the pattern of species occurrence.Partial ordination detected residual differences in vegetation among the different floodplain types after accounting for the effects of the measured environmental variables. Grain size distribution is discussed as a further factor that might influence species composition. Copyright © 2004 John Wiley & Sons, Ltd.

Spatial distribution characteristics of organic matter and total nitrogen of marsh soils in river marginal wetlands

Contents of soil organic matter (SOM) and total nitrogen (TN) in the surface soils and subsurface soils were measured in five types of floodplains classified with different flood frequencies in river marginal wetlands of Erbaifangzi, China, in 1999. Contour maps and profile maps were constructed to describe the spatial distribution of SOM and TN in order to identify the influences of flood frequency on them. Results showed that spatial distributions of both SOM and TN were very similar in soil profiles (0–120 cm) of the five areas, decreasing gradually with depth except an accumulation peak in the flooded floodplain (B area). Also, the accumulation peak in the soil profile of B area was relevant to water table, nitrogen leaching, denitrification and mineralization. However, their horizontal distributions in surface soils (0–10 cm) were different in the five areas. Although the flood could bring the deposit of nutrients and sands, the highest content of SOM or TN did not appear in B area but in the floodplain with certain flood frequency. For example, SOM content (6.76%) in 5-year floodplain wetland was highest, and the highest content of TN (3666.4 mg/kg) appeared in 1-year floodplain wetland. However, SOM and TN contents in soils of B area were 4.08% and 2605.4 mg/kg, respectively. Soil clay content, wetland plant ( Phragmites australis) litter inputs, soil moisture and water table greatly affected the spatial distribution of SOM and TN in floodplain wetlands. The ratios of carbon to nitrogen of wetland soils in this region were relatively lower than those in paddy soils. SOM and TN contents were significantly correlated with total phosphorus (TP) contents in floodplain wetlands except the 100-year floodplain wetland, but they were significantly influenced by soil pH values only in B area. Denitrification and ammonia volatilization were the main mechanisms resulting in nitrogen loss of surface soils in B area. Flood frequency significantly influenced the ecological functions such as nutrient retention and water quality maintenance of floodplains.

Ecological and Floristic Analyses of Vascular Plants along a Gradient on Disturbed Serpentinite on Opposing Slopes in Staten Island, NY

LEVINE, M. E. AND A. M. GRELLER (Department of Biology, Queens College, CUNY, Flushing, NY 11367). Ecological and floristic analyses of vascular plants along a gradient on disturbed on opposing slopes in Staten Island, NY. J. Torrey Bot. Soc. 131:71-94. 2004.-Bloodroot Valley, in central Staten Island, southeastern New York State, has unusual vegetation. It is a highly disturbed area in which rubble has been deposited on till-covered bedrock. Bloodroot Valley is reputed to contain the only wild, albeit augmented, population of Sanguinaria canadensis found on Staten Island. The hypothesis of the study was that variation in observed plant associations would correlate with variations in soil properties. This study compared two distinct vegetative patterns on opposing slopes, existing within meters of each other, and each associated with different soil properties. Human disturbance in one area of Bloodroot Valley has fostered a unique soil condition that reflects a blend of features of soils, anthropogenic calcium deposits and river floodplains. Vegetation on the west slope in Bloodroot Valley contains neither serpentinite nor flora typical of the adjacent mixed oak forest, but rather, a floodplain type plant association with Hydrophyllum virginianum as dominant.

An evaluation of the benefits of lowland river-floodplain rehabilitation (the Rhine, the Netherlands).

Water quality of the Rhine has improved significantly since 1970, but its landscape was highly altered with a shortage of dynamic processes, characteristic landscape elements and biodiversity. During the last decade manifold floodplain rehabilitation projects have been planned and realized in the Netherlands. Yardsticks for recovery are naturalness, biodiversity and spatial connectivity, but actually there is no clear end-point or reference to assess its success. Constraints for rehabilitation are flood protection and shipping. The benefits of a subset of rehabilitation projects situated along the largest flee-flowing Rhine branch, that has an open connection to the North Sea, were assessed at two landscape levels: the project itself (1-10 kin) and the river stretch (> 100 km) using five parameters (landscape mosaic, vegetation, macro-invertebrates, fish and birds). The assessment yielded comparable marks among the parameters, so the overall appraisal is considered to be robust. However, the scarcity and incompleteness of the underlying data forced us to use a fair amount of expert judgement. Generally terrestrialized floodplains have been set back to more frequently flooded (semi-) aquatic habitats. Especially dynamic, shallow water habitats emerged. Vegetation quickly responded when management changed from farming to extensive grazing. Rheophilic fish and macro-invertebrates immediately colonised side channels. At present, more than 40 % of the present floodplain area consists fo deep water and 30 % of agricultural land and built up areas, and typical floodplain habitats (such as shallow riverbed, river banks and dunes and herbaceous floodplains) are still underrepresented. Within rehabilitation projects the landscape significantly changed, but the projects do not yet significantly contribute to the ecological recovery of the whole river stretch. Moreover, biological indicators point to a moderate or even poor ecological state.

Flood channel morphology of a quiet river, the Lachlan downstream from Cowra, southeastern Australia

Detailed geomorphic mapping and sediment analyses of floodplain features were undertaken on a 30-km reach of the Lachlan River in southeastern Australia. The reach is located in the transitional zone between the southern Great Dividing Range and extensive alluvial plains to the west. The channel resembles other fine-grained, low-energy, alluvial channels; it is muddy, narrow and deep, and meanders irregularly. It contains fine-grained accreting bench deposits, and, in places, is influenced by inherited fluvial forms, both of which indicate long-term channel stability. By contrast, the floodplain exhibits features that have been attributed elsewhere to catastrophic flood flows, including elliptical scour scars (“swirl pits”), cobble and gravel deposits, large chutes and chute bars, zones of floodplain stripping, flood levees and multiple flood channels. Sorting and texture of floodplain sediments generally increases with height above the bed, although deposits are variable and poorly sorted. Indications of recent fluvial activity at several levels above the bed are confirmed by aerial photographs dating from 1954, although changes to the channel position have been small. The alluvial facies model displays a compound floodplain, in which a stable, low-energy channel is inset within a high-energy, flood-dominated floodplain. This interpretation is consistent with streamflow and documentary evidence of recurrent large floods since 1839, which have a return period of <10 years on both the partial and annual series. Natural streamflow is characterised by high annual variability and a steep flood growth curve. In such systems, flow variability, together with stream power and sediment characteristics, appears to be an important determinant of floodplain type.

Floodplain sedimentation: inherited memories

Swampy inherited floodplains are found throughout the steppe and forest steppe over the Russian Plain. These floodplains were formed during the Late Glacial/Holocene transition on the relicts of large meandering palaeochannels in the former periglacial zone as a result of dramatic decrease in river channel widths (up to 1/15). Inherited floodplains were only partly reworked by the activity of the Holocene rivers. The remnants of the ancient fluvial relief control the flow hydraulics and sediment transport delivery to the river channels on the wide floodplains, causing sediment discontinuity. Such discontinuity reaches its maximum in the chain-of-lakes channels, and decreases with the evolution of the inherited floodplain into a typical floodplain with developed continuous channels.

Луга Северо-Восточного Алтая

The North-Eastern Altai is an ultra-humid area with climax vegetation represented by tall-herb fir (Abies sibirica) dark-coniferous forest. Its meadows belong to the class Molinio-Arrhenatheretea. The typical asso­ciation Aegopodio podagrariae—Dactyletum glomeratae originates in the watershed clearings after climax forests whereas ass. Hyperici perforati—Agrostietum giganteaereplaces the previous one under mowing and grazing. The Molinietalia wet meadows are widespread in the river valleys. The meadows of ass. Cirsio heterophylli—Calama­grostietum langsdorffii occur on wet soils in small depressions and along floodplain mire margins, and ass. Ca­rici ovalis—Deschampsietum cespitosae comprises typical floodplain hay-meadows on moist, nutrient-rich soils.

Ground‐penetrating radar and sedimentological analysis of Holocene floodplains: Insight from the Tuross valley, New South Wales

Ground‐penetrating radar (GPR) has been used on an array of floodplain types on the lower Tuross River, in southeastern New South Wales, as part of an investigation into controls on channel‐floodplain relationships. Ground‐penetrating radar transects from two floodplains are presented, along with sedimentological detail from trenches dug along the profiles at key locations. Sedimentological investigations showed that 100 MHz antenna gave an approximation of overall bedding trends in the upper 3 m when automatic gain control processing was used. Spreading and exponential compensation processing provided insight into textural changes associated with increased silt content distal of the levee crest. One trench showed that thinning beds were responsible for onlapping reflectors. Signal attenuation at ∼4 m depth below the raised floodplain surface resulted from a >50 cm‐thick bed of sandy clay. The close integration of GPR and sedimentological data produced an excellent dataset, that enabled form‐process associations and floodplain evolution to be established for these sandy floodplains. However, accurate subsurface assessment and interpretation must stem from carefully combined GPR and sedimentological datasets.

An outline on lateral fish migrations within the Central Delta of the Niger River, Mali

The lateral migration of fishes was studied during one entire flood cycle (1991) in a typical floodplain sector of the Central Delta of Niger at Batamani, Mali. The intensity and temporal course of migrations, as well as the species and size composition of migrants, were found to be correlated with the hydrological regime (river and floodplain water levels, direction and velocity of water flow in a temporary canal). Four different types of migratory patterns were described and their typical representatives indicated. The significant role of the river as a spawning site and that of the flood plain as a nursery for most locally important fishes was also accentuated.

Floodplain Change in the Glenmalure Valley, South-east Leinster

The Glenmalure Valley is one of several U-shaped valleys which drain the eastern flanks of the Wicklow Mountains, 45km south west of Dublin. Five channel and floodplain reaches are recognised along a 25km stretch of the Glenmalure River on the basis of spatial changes in stream power and sediment load characteristics. The downvalley sequence of floodplain types within the river is atypical of that commonly associated with decreasing slope and sediment calibre downstream. Radiocarbon dating together with the use of anomalous concentrations of heavy metals, which are used as stratigraphic indicators of alluvial deposition post 1800, also reveal temporal changes in the rate of Holocene floodplain development within the valley. Downstream changes in floodplain processes within the valley are explained, therefore, in terms of spatial and temporal changes in the river's ability to adjust its slope, form and bed texture within the constraints of geological and Pleistocene geomorphic inheritance. The presence of a bedrock basin in the valley floor profile, infilled by Pleistocene lacustrine deposits, is believed to have caused a local change in base level leading to a significant reduction in valley slope and local stream power in the middle reaches of the valley. The subsurface bedrock form and the Pleistocene palaeolake also had a significant impact on coarse sediment transport, storage and transfer through the river system and hence on the ability of the Holocene river to regrade its slope and laterally rework Pleistocene valley fills for floodplain construction.

Indonesia's major freshwater lakes: A review of current knowledge, development processes and threats

Indonesia has over 500 lakes, varying from deep tectonic basins to volcanic, glacial and ephemeral floodplain types, but the paucity of data is striking. Hydrological data, for example, are scarce,...