Stream Flood Research Articles

Risk based urban watershed management under conflicting objectives

Ecological impairment and flooding caused by urbanization can be expressed numerically by calculating the risks throughout the watershed (floodplain) and along the main stems of the streams. The risks can be evaluated in terms of the present and/or future. This article describes the methodologies for ascertaining the risks in the Geographical Information Systems (GIS) environment. The objectives of urban flood controls and ecological preservation/restoration of urban waters are often conflicting and, in the past, the sole emphasis on flood control led to destruction of habitat and deterioration of water quality. An optimal solution to these two problems may be achieved by linking the risks to the concepts of risk communication, risk perception, and public willingness to pay for projects leading to ecological restoration and ecologically sustainable flood control. This method is appropriate because, in each case, public funds are used and the projects require approval and backing of policy makers and stakeholders. This article briefly describes a research project that attempts to resolve the conflict between the flood protection and stream ecological preservation and restoration and suggests alternative ways of expressing benefits of urban stream flood control and restoration projects.

Circulation and Brackish Water Dispersal in a Coastal Lagoon of Southwest Taiwan

Modest observations and numerical experiments were conducted to investigate circulation and brackish water dispersal in a coastal lagoon southwest of Taiwan. The Chi-Ku Lagoon, partially shielded from the sea by a string of sandbar barriers with two entrances among them, receives modest and episodic runoff from Chi-Ku Stream. Flood and ebb tidal streams entering and leaving the two entrances are found to converge and diverge in a flow stagnation area inside the lagoon. Under weak wind conditions, brackish water is preferentially retained in the flow stagnation area. Besides the observations, scenario runs using a three-dimensional numerical model also indicate strong modulation by monsoon winds. Both summer southwest monsoon and winter northeast monsoon reduce brackish water retention; the latter is found to be more effective.

Biotic and abiotic effects of flash flooding in a montane desert stream

Flash floods in desert streams can be more sudden, brief, and severe compared to floods in mesic streams. To determine their biotic and abiotic effects, substrate composition, organic detritus abundance, and aquatic animal taxonomic richness and abundance were measured 8-16 d before and 7d after a flash flood in a 122 m reach of a montane desert stream (Chihuahuan Desert, USA). The flash flood severely altered channel morphology by scouring and depositing substrates, but it did not change the overall abundance of any substrate particle size class. The flood removed most coarse detritus from the stream reach, although the quantity of organic particles <2 mm was unchanged. High losses were observed in most animal taxa (95 % overall), and reach-wide taxonomic richness was reduced from 35 to 21 taxa. Ephemeroptera were entirely eliminated from the study reach. The taxon experiencing the lowest percent loss (the belostomatid hemipteran Abedus herberti, 14 % loss) is known to possess behavioral mechanisms for flash flood avoidance. Compared to studies of flooding in mesic streams, this study suggests that flash floods in montane desert streams cause greater mortality in animal populations and remove more detritus. Ecologically, these high local mortality rates stress the importance of recolonization mechanisms. Evolutionarily, flash floods provide a strong selection pressure that may influence the genetic structure of populations.

Coupling between hillslopes and channels in upland fluvial systems: implications for landscape sensitivity, illustrated from the Howgill Fells, northwest England

The sensitivity of upland fluvial systems depends on the magnitude and frequency of sediment and flood producing events, modified by the internal coupling characteristics of the system. This paper assesses the role of hillslope/channel coupling for the sensitivity of upland geomorphic systems, using evidence from a 30-year monitoring programme of geomorphic change in the Carlingill valley, Howgill Fells, northwest England. In the hillslope zone, there is little sediment supply to the stream system. Locally, slope failures occur in response to extreme events (six such events in 30 years within the ca. 6 km 2 Carlingill valley). In the footslope coupling zone, basally induced gullies are major sediment sources to the stream. Sediment-production events occur ca. 30 times per year, feeding sediment to basal debris cones. Stream floods which can entrain these sediments occur once every ca. 2–5 years. Stream channel morphology is adjusted to this regime. Downstream of gullies, channels are wide and braided; elsewhere they are narrow and single-thread. As the gullies develop, however, this coupling weakens and the eroding slopes eventually stabilise by revegetation. Over the 30-year monitoring period, there has been a progressive trend towards gully stabilisation, and an associated reduction in channel instability. Massive destabilisation may occur in response to rare extreme flood events. Such an event (return period >100 years) occurred in neighbouring Langdale and Bowderdale valleys in June 1982. That event destabilised the system, causing slope failures, fan deposition, and in some places, a switch in channel style to wide braided channels. Since 1982 there has been a progressive recovery by slope stabilisation and single-thread sinuous channels have become reestablished. A different style of extreme event occurred in Carlingill in October 1998, in response to the wettest week in the 30-year period. A slope failure fed debris flows 400 m downslope, almost coupling with the channel system. Future climatic change could render the system prone to destabilisation, through either extreme flood events or through major slope failures.

A review of geological records of large tsunamis at Vancouver Island, British Columbia, and implications for hazard

Large tsunamis strike the British Columbia coast an average of once every several hundred years. Some of the tsunamis, including one from Alaska in 1964, are the result of distant great earthquakes. Most, however, are triggered by earthquakes at the Cascadia subduction zone, which extends along the Pacific coast from Vancouver Island to northern California. Evidence of these tsunamis has been found in tidal marshes and low-elevation coastal lakes on western Vancouver Island. The tsunamis deposited sheets of sand and gravel now preserved in sequences of peat and mud. These sheets commonly contain marine fossils, and they thin and fine landward, consistent with deposition by landward surges of water. They occur in low-energy settings where other possible depositional processes, such as stream flooding and storm surges, can be ruled out. The most recent large tsunami generated by an earthquake at the Cascadia subduction zone has been dated in Washington and Japan to AD 1700. The spatial distribution of the deposits of the 1700 tsunami, together with theoretical numerical modelling, indicate wave run-ups of up to 5 m asl along the outer coast of Vancouver Island and up to 15–20 m asl at the heads of some inlets. The waves attenuated as they moved eastward along Juan de Fuca Strait and into Puget Sound and the Strait of Georgia. No deposits of the 1700 event or, for that matter, any other tsunami, have yet been found in the Strait of Georgia, suggesting that waves were probably no more than 1 m high in this area. If a tsunami like the 1700 event were to occur today, communities along the outer Pacific coast from southern British Columbia to northern California would be severely damaged. There would be little time to evacuate these communities because the tsunami would strike the outer coast within minutes of the first ground shaking. Fortunately, such tsunamis are infrequent — perhaps as few as seven have occurred in the last 3500 yr. Other tsunamis that are much smaller and more localized, although probably more frequent, are caused by local crustal earthquakes and landslides along the British Columbia coast. Two such tsunamis have occurred in British Columbia in recent years, one in 1946 in the Strait of Georgia and another in 1975 at the head of a fiord on the northern mainland coast.

The nature of small-scale flooding, muddy floods and retention pond sedimentation in central Belgium

This study investigates the spatial variation of small-scale flooding and muddy floods in rural areas in a medium sized study area (5516 km 2) and the linkage with controlling factors. A questionnaire set up in central Belgium indicates that 43% of the municipalities have to deal from time to time with muddy floods generated from direct runoff from arable land and 36% with flooding of permanent streams. A strong relation exists between the nature of the problem and the site in relation to topography and landuse. Areas suffering from muddy floods have significantly steeper cultivated slopes compared to areas suffering only from small-scale flooding. The high spatial and temporal frequency of small-scale flooding and muddy floods results in emotional and significant economic damage to private households. As a control measure more than 100 retention ponds have been constructed with 50 more to be built in the near future. The mean cost for the construction of a retention pond amounts to 380,000 EURO. These retention ponds store large quantities of sediment from runoff events and must thus be dredged regularly with costs of the order of 1.5 million EURO yearly. The dredged sediment volumes can be used to assess and predict sediment yield for these drainage basins; values vary between 0.19 and 6 m 3 ha −1 year −1 for basins ranging from 25 to 5000 ha.

Heavy Rainfall: Contrasting Two Concurrent Great Plains Thunderstorms

Abstract Measurement and forecasting of heavy rainfall requires interpretation of the small differences in the storm environment that distinguish a major flood-producing rainfall event from a relatively harmless storm system. This case study will examine some of the small differences in the storm environment that lead to a heavy rainfall event. On 8 July 1994 two storm systems developed in close proximity to each other in central Oklahoma. One of the storms developed into a squall line and produced low storm total precipitation accumulations. The other was a slow-moving multicellular storm that produced storm total precipitation of more than 130 mm and small stream flooding. The storms exhibited contrasting measurement errors in the operational WSR-88D rainfall products, with underestimation for the heavy rain event and overestimation for the squall line. The interactions of synoptic, mesoscale, and storm-scale processes for the 8 July storms are examined through analyses of WSR- 88D reflectivity and Dopp...

A cost effective approach to stormwater management? source control and distributed storage

Rapid urbanisation and its consequent increase in impermeable surface areas and changes in land use has generally resulted in problems of flooding and heavy pollution of urban streams and other receiving waters. This has often been coupled with ground water depletion and a threat to water resources. The first part of this paper presents an alternative drainage philosophy and strategy which mimics nature's way by slowing down (attenuating) the movement of urban runoff. This approach results in cost-effective, affordable and sustainable drainage schemes. The alternative strategy can be described as one of prevention rather than cure by effecting controls closer to source rather than the traditional approach which results in the transfer of problems downstream, resulting in its cumulation and the need for large scale, centralised control. The second part describes a research project which has been launched in order to quantify the cost and operational benefits of source control and distributed storage. Details of the methodology of the modelling and simulation processes which are being followed to achieve this target are presented.

Coupling between hillslope gully systems and stream channels in the Howgill Fells, northwest England: temporal implications/Le couplage des systèmes de ravins et des lits fluviaux dans les Howgill Fells, nord-ouest de l'Angleterre : signification temporelle

Abstract Hillslope gullies, cut in glacial till, supply sediment to the channel of Carlingill, a small upland stream in the Howgill Fells, northwest England. Coupling between the two zones is fundamental to the dynamics of the whole system. Gully development is initiated by stream erosion at the slope base, and maintained by the periodic removal of the eroded sediment by stream floods. As gully development proceeds the strength of coupling between gully and stream channel decreases, and is ultimately broken, leading to the stabilisation of the gullied slopes by revegetation. The coarse sediment supplied by the gullies becomes the stream bedload controlling the stream dynamics. The channels in zones away from gully sediment sources tend to be narrow, single-thread, relatively stable channels. Those downstream of gully sites tend to be wide, often braiding and unstable. Monitoring of sediment movement between gullies and stream channels, at two spatial scales, over temporal scales of 6 and 25 years, has identified a decrease in coupling with progressive gully development, causing a decrease in the frequency of sediment supply events and an increase in the complexity of sediment storage within the system. Over the longer term, two phases of gully development can be identified. Large gullies developed in the late Holocene, probably ca 1 000 yrs BP, which overloaded the system, causing deposition of large debris cones and alluvial fans. More recently, over the last ca 200 years, smaller gullies developed and locally stabilised. Their transient influence on channel morphology has been identified through the application of lichenometry to the valley floor morphology. Coupling relationships are fundamental to the geomorphology of slope and channel systems in this environment, over a range of timescales.

A cost effective approach to stormwater management? Source control and distributed storage

Rapid urbanisation and its consequent increase in impermeable surface areas and changes in land use has generally resulted in problems of flooding and heavy pollution of urban streams and other receiving waters. This has often been coupled with ground water depletion and a threat to water resources.The first part of this paper presents an alternative drainage philosophy and strategy which mimics nature's way by slowing down (attenuating) the movement of urban runoff. This approach results in cost-effective, affordable and sustainable drainage schemes. The alternative strategy can be described as one of prevention rather than cure by effecting controls closer to source rather than the traditional approach which results in the transfer of problems downstream, resulting in its cumulation and the need for large scale, centralised control.The second part describes a research project which has been launched in order to quantify the cost and operational benefits of source control and distributed storage. Details of the methodology of the modelling and simulation processes which are being followed to achieve this target are presented.

Genesis of crystal-rich volcaniclastic facies in the Permian red beds of the Central Pyrenees (NE Spain)

The Permo-Carboniferous volcanism of the Central Pyrenees developed in subaerial conditions, and is mainly represented by the products of explosive eruptions of calc-alkaline silicic magmas occasionally associated with calderaforming events. The sedimentological record of the Permo-Carboniferous basins of the Central Pyrenees is characterized by the abundance of crystal-rich volcaniclastic deposits reflecting a high crystal content in the erupting magmas (18–40 vol.%). Sedimentation during the Early Permian was dominated by massflows, stream floods and braided channels, organised in poorly developed alluvial fans at basin margins. A wide spectrum of crystal-rich deposits can be identified in the Permian terrigenous red beds. The grouping of these deposits into facies and facies associations, allows the recognition of several volcaniclastic marker horizons extending through the Central Pyrenees. These can be used to establish stratigraphical correlations between the different Permo-Carboniferous basins. The study of these crystal-rich volcaniclastic deposits has revealed that the Lower Permian crystal-rich voleaniclastic deposits of the Central Pyrenees originated from pyroclastic and reworking processes that sometimes acted simultaneously. Pyroclastic deposits derived from high intensity explosive magmatic eruptions of rhyodacitic and rhyolitic crystal-rich magmas. These eruptions generated high eruption columns that occasionally collapsed, giving rise to the formation of widespread pyroclastic flows and associated pyroclastic surges. The entrance of the eruption columns into the atmosphere had a significant effect on the local weather, provoking sporadic storms that led to reworking of pyroclasts by rainfall run-off during eruption. Different crystal concentration processes acted in the eruption columns and in the subsequent pyroclastic flows and overriding ash clouds, producing the accumulation of a high volume of crystals in the resulting deposits. Reworking and redeposition of pyroclastic deposits by fluvial processes further enhanced crystal concentration.

Heightened North Pacific Storminess during Synchronous Late Holocene Erosion of Northwest Alaska Beach Ridges

A progradational regime of falling sea level and/or high sediment input has produced extensive beach ridge plains in northwest Alaska during the last 4000 yr. Eleven Chukchi Sea beach ridge complexes, oriented at various angles to wind fetch, provide a cumulative history of longshore transport and erosion. Archaeological and geological upper limiting radiocarbon ages ( n = 59) allow correlations between depositional units on seven beach ridge complexes. Progradation started 4000 yr B.P. at nearly all complexes, as eustatic sea level stabilized. Two disconformities or truncations are found on most of the complexes, providing time-parallel storm horizons, dated at 3300-1700 and 1200-900 14C yr B.P. Between 1700 and 1200 14C yr B.P. most of the complexes prograded, indicating the predominance of less-stormy conditions. Modern synoptic patterns that produce Chukchi beach ridge erosion are linked to northerly shifts in North Pacific storm tracks. The regionwide beach ridge erosional truncations correlate with records of glacier expansion, heightened precipitation evident in tree-rings, stream flooding, and shelf deposits reworked by storm surges.

Pliocene subaqueous fans and Gilbert‐type deltas in maar crater lakes, Hopi Buttes, Navajo Nation (Arizona), USA

ABSTRACTMaar craters of the Mio‐Pliocene Hopi Buttes volcanic field of Arizona formed within a broad playa system, and accumulated a variety of lacustrine sedimentary deposits. Many craters initially held isolated, groundwater‐fed lakes. Ephemeral streams crossing the playa entered some of the lake‐filled craters, and built coarse grained Gilbert‐type deltas and subaqueous fans along the margins of these craters. The small, coarse grained fans and deltas have many features in common with much larger coarse grained deltaic and fan deltaic deposits. However, the local production of coarse grained volcanic sediment, low gradients in the local stream catchment, steep subaqueous relief and the small size of the receiving ‘basins’resulted in a unique combination of features. Cone‐shaped subaqueous fans initially formed at the mouths of incised feeder streams. The fans are small accumulations of steeply dipping gravelly tephra that consist almost entirely of overlapping lobes constructed by density‐modified grain flows. Gravelly Gilbert‐type tephra deltas formed in brimfull craters fed by a freely migrating feeder stream. They are concave lakeward, mimicking the underlying crater wall topography. Complex deltaic geometries are defined by topset strata that steeply onlap tall foreset beds. They suggest that feeding stream floods caused rapid and comparatively large variations in lake level within the small crater lakes. Bed‐specific carbonate alteration is common, and probably resulted from both influx of detrital carbonate across the playa and alteration of tephra beds by carbonate‐saturated lakewaters during between flood periods of high net evaporation.

Soil‐landscape and climatic relationships in the middle Miocene of the Madrid Basin

ABSTRACTThe Miocene alluvial‐lacustrine sequences of the Madrid Basin, Spain, formed in highly varied landscapes. The presence of various types of palaeosols allows assessment of the effects of local and external factors on sedimentation, pedogenesis and geomorphological development. In the northern, more arid, tectonically active area, soils were weakly developed in aggrading alluvial fans, dominated by mass flows, reflecting high sedimentation rates. In more distal parts of the fans and in playa lakes calcretes and dolocretes developed; the former were associated with Mg‐poor fan sediments while the latter formed on Mg‐rich lake clays exposed during minor lake lowstands.The north‐east part of the basin had a less arid climate. Alluvial fans in this area were dominated by stream flood deposits, sourced by carbonate terrains. Floodplain and freshwater lake deposits formed in distal areas. The high local supply of calcium carbonate may have contributed to the preferential development of calcretes on the fans. Both the fan and floodplain palaeosols exhibit pedofacies relationships and more mature soils developed in settings more distant from the sediment sources. Palaeosols also developed on pond and lake margin carbonates, and led to the formation of palustrine limestones.The spatial distributions and stratigraphies of palaeosols in the Madrid Basin alluvial fans suggest that soil formation was controlled by local factors. These palaeosols differ from those seen in Quaternary fans, which are characterized by climatically induced periods of stability and instability.

Observations of desert flood bores

AbstractFlood bores have been measured in desert stream floods. The bores were steep and small pebbles were observed to be pushed ahead. Bore velocity changed downstream and was controlled by local channel geometry. In narrow reaches, the bore advanced at rates twice those of wide reaches. Mean bore velocity was about 50 per cent of that of mean flow at peak flood discharge. The surfaces of shallow bores were covered by air foams. This was not the case in deeper, faster examples.

THE NATURE AND RATE OF ALLUVIAL FAN AGGRADATION IN A HUMID TEMPERATE ENVIRONMENT, NORTHWEST WASHINGTON

Comparatively little is known about net aggradation on alluvial fans, despite fan construction wherever sediment-delivery rates from uplands exceed sediment-removal rates from receiving basins. In January 1983, 20 alluvial fans in the forested Cascade foothills, northwest Washington, experienced net aggradation in response to debris torrents and stream floods triggered by intense warm rains falling on antecedent snow. Five trenches were excavated to 5 m depth on the Mills Creek fan to place the 1983 event in temporal perspective. The deposits reflect normal streamflow, hyperconcentrated streamflow and debris torrent (flow) conditions. One trench revealed residues of 7 events since 1720 BP. Net rates of Holocene aggradation, based on sediments overlying late Pleistocene fluvioglacial deposits, average 0.42 m ka-1. Net rates for later Holocene time range from 2.17 m ka-1 since 1720 BP to 2.36 m ka-1 since 430 BP. These recent rates exceed the local value for the entire Holocene and rates for humid temperate...

Controls on synchronous ephemeral- and perennial-river sedimentation in the middle sandstone member of the Triassic Chinle Formation, northeastern New Mexico, U.S.A.

The middle sandstone member of the upper Triassic Chinle Formation in northeastern New Mexico consists of ephemeral-river deposits along the Front Range adjacent to the Ancestral Rocky Mountains and perennial braided-river deposits on the Plains to the east. The two fluvial systems were synchronous; the ephemeral rivers existed as transverse tributaries to a perennial trunk system that flowed from south to north. Proximal ephemeral-stream deposits are characterized by 60–80 m thick sequences of coarse-grained, siliciclastic sediments deposited principally by overbank sheetflooding. Facies associations are dominated by sandstone with horizontal stratification and subordinate sets of tabular-tangential and trough cross-stratification. Incised streamflood deposits are represented by channeled conglomerates and single-story, massive and trough cross-stratified sandstones. Distal ephemeral-stream deposits are distinguished by their lenticular geometries, thicknesses of 20–30 m, and sedimentary structures indicative mainly of lower-flow-regime stream flooding. Channeled conglomerates and trough cross-stratified and parallel-stratified sandstones are capped by trough cross-laminated and subordinate horizontally stratified sandstones. Facies associations in the deposits of the trunk system are comparable to those of the Platte and South Saskatchewan braided rivers. Sets and cosets of tabular-tangential or trough cross-stratified conglomerate and sandstone are separated by variable thicknesses of horizontally stratidied sandstone. These facies dominate 10–30 m thick, sheet-like, siliciclastic bodies that are traceable laterally for tens of kilometers and are separated by comparable or lesser thicknesses of red mudstone. Both extrabasinal (allocyclic) and intrabasinal (autocyclic) controls influenced sandstone body geometries in the middle Chinle Formation. Uplift and subsidence determined the position of base level that, in turn, determined the nature of autocyclic processes. Adjacent to the Ancestral Rocky Mountains, sediment yield was great resulting in accumulation of sheetflood deposits above base level, thereby promoting local incision. Under these conditions and with a continuously rising base level, lenticular, coarse-grained sediment body geometries were produced along the Front Range. On the Plains, sediment yield was moderate and subsidence rates were slow. Bedload sediment accumulated to, but not above base level, thereby promoting avulsion and the development of thin, sheet-like coarse-grained sediment bodies. The contrast between the two coexisting fluvial sedimentation styles is attributed to differences in runoff. Adjacent to the Ancestral Rocky Mountains, seasonal rainfall resulted in ephemeral flow, whereas on the Plains, flow was perennial due to groundwater discharge from the highlands to the west.

Megafaunal butchering at Lubbock Lake, Texas: A taphonomic reanalysis

Five seasons of excavation in Feature Area 2-1 of the Lubbock Lake Landmark, Texas, exposed a megafaunal bone accumulation in sands and gravels deposited by a late Pleistocene meandering stream. Many bone specimens exhibit evidence of alteration, supporting interpretation of the feature as an in situ, secondary meat-processing area; the gravels are interpreted as the point bar of a meandering stream. Faunal remains lying stratigraphically above the point bar have been considered to form a separate, noncultural feature produced by stream flooding. However, rose diagrams and analysis of adjusted residuals demonstrate that a statistically significant amount of bone in each feature is aligned along axes of preferred orientation. Further, the orientation patterns and statistical analyses of both features exhibit the same trends, suggesting that the same processes affected both. Although the evidence does not rule out a role of human behavior, it does demonstrate that stream currents significantly influenced feature structure.

Morphology and Facies of Alluvial Fans in Kadhmah Bay, Kuwait

ABSTRACT The Jal-Az-Zor escarpment, some 80 km long and up to 145 m high, is a striking feature northwest of Kuwait Bay. Several alluvial fans are developed at the foot of the escarpment, and they terminate in playa and sabkha sediments towards Kadhmah Bay. The Quaternary sediments of the alluvial fans are divided into three facies: proximal, midfan, and distal fan facies, and they vary from conglomerates to sandstones to mudrocks. The Jal-Az-Zor alluvial fan sediments coarsen up in the proximal part, but fine upward in the distal region. Poorly sorted but highly imbricated conglomerates and pebbly sandstones with little stratification characterize the proximal region. Sediments of the midfan area show crossbedding and parallel lamination. Distal fan sediments are typically planar-laminated sa ds interbedded with lacustrine mud of playa origin. The alluvial fans have resulted from stream flooding and are composed of stacked depositional units.

Manual of surface drainage engineering, vol. 2. Stream flow engineering and flood protection

Manual of surface drainage engineering, vol. 2. Stream flow engineering and flood protection