Review of 'Development of a Precipitation-Area Curve for Warning Criteria of Short-Duration Flash Flood' submitted to NHESS by Deg-Hyo Bae, Moon-Hwan Lee, Sung-Keun Moon

2017 ◽  
Author(s):  
Anonymous
Keyword(s):  
Short Duration ◽  
Flash Flood ◽  
Precipitation Area ◽  
Warning Criteria

scholarly journals Development of a precipitation–area curve for warning criteria of short-duration flash flood

2018 ◽  
Vol 18 (1) ◽  
pp. 171-183 ◽  
Author(s):  
Deg-Hyo Bae ◽  
Moon-Hwan Lee ◽  
Sung-Keun Moon
Keyword(s):  
Soil Moisture ◽  
South Korea ◽  
Short Duration ◽  
Flash Flood ◽  
Threshold Function ◽  
Flood Events ◽  
Small Stream ◽  
Flood Warning ◽  
Precipitation Area ◽  
Moisture Conditions

Abstract. This paper presents quantitative criteria for flash flood warning that can be used to rapidly assess flash flood occurrence based on only rainfall estimates. This study was conducted for 200 small mountainous sub-catchments of the Han River basin in South Korea because South Korea has recently suffered many flash flood events. The quantitative criteria are calculated based on flash flood guidance (FFG), which is defined as the depth of rainfall of a given duration required to cause frequent flooding (1–2-year return period) at the outlet of a small stream basin and is estimated using threshold runoff (TR) and antecedent soil moisture conditions in all sub-basins. The soil moisture conditions were estimated during the flooding season, i.e., July, August and September, over 7 years (2002–2009) using the Sejong University Rainfall Runoff (SURR) model. A ROC (receiver operating characteristic) analysis was used to obtain optimum rainfall values and a generalized precipitation–area (P–A) curve was developed for flash flood warning thresholds. The threshold function was derived as a P–A curve because the precipitation threshold with a short duration is more closely related to basin area than any other variables. For a brief description of the P–A curve, generalized thresholds for flash flood warnings can be suggested for rainfall rates of 42, 32 and 20 mm h−1 in sub-basins with areas of 22–40, 40–100 and > 100 km2, respectively. The proposed P–A curve was validated based on observed flash flood events in different sub-basins. Flash flood occurrences were captured for 9 out of 12 events. This result can be used instead of FFG to identify brief flash flood (less than 1 h), and it can provide warning information to decision-makers or citizens that is relatively simple, clear and immediate.

scholarly journals Development of a Precipitation-Area Curve for Warning Criteria of Short-Duration Flash Flood

2017 ◽  
Author(s):  
Deg-Hyo Bae ◽  
Moon-Hwan Lee ◽  
Seun-Keun Moon
Keyword(s):  
Soil Moisture ◽  
South Korea ◽  
Short Duration ◽  
Flash Flood ◽  
Threshold Function ◽  
Flood Events ◽  
Small Stream ◽  
Flood Warning ◽  
Precipitation Area ◽  
Moisture Conditions

Abstract. This paper presents quantitative criteria for flash flood warning that can be used to rapidly assess flash flood occurrence based on only rainfall estimates. This study was conducted for 200 small mountainous sub-catchments of the Han River basin in South Korea because South Korea has recently suffered many flash flood events with short duration. Flash Flood Guidance (FFG) was defined as the depth of rainfall of a given duration required to cause minor flooding at the outlet of a small stream basin and was estimated using threshold runoff (TR) and antecedent soil moisture conditions in all the sub-basins. The soil moisture conditions were estimated during the flooding season, i.e., July, August and September, over 7 years (2002~2009) using the Sejong University Rainfall Runoff (SURR) model. A ROC analysis was used to obtain optimum rainfall values and a generalized precipitation-area curve (P-A curve) was developed for flash flood warning thresholds. The threshold function was derived as P-A curve due to the reason that the precipitation threshold with short duration is highly related to basin area than any other variables. Generalized thresholds for flash flood warning were obtained for rainfall rates of 42, 32 and 20 mm/h in sub-basins with areas of 22~40 km2, 40~100 km2 and > 100 km2, respectively. The proposed P-A curve was validated based on actual flash flood events in different sub-basins, which showed the viability of the proposed criteria to capture actual flash floods using only the rainfall rate and area of a sub-basin. The key advantage of this method is possible to issue flash flood warnings without the need to run entire hydro-meteorological model chains in the region where the short-duration flash flood frequently occurred.

scholarly journals Towards advancing scientific knowledge of climate change impacts on short-duration rainfall extremes

2021 ◽  
Vol 379 (2195) ◽  
pp. 20190542 ◽  
Author(s):  
Hayley J. Fowler ◽  
Haider Ali ◽  
Richard P. Allan ◽  
Nikolina Ban ◽  
Renaud Barbero ◽  
...  
Keyword(s):  
Climate Change ◽  
Short Duration ◽  
Large Scale ◽  
Flash Flood ◽  
Extreme Rainfall ◽  
Heavy Precipitation ◽  
Climate Modelling ◽  
Large Scale Circulation ◽  
Rainfall Extremes ◽  
International Coordination

A large number of recent studies have aimed at understanding short-duration rainfall extremes, due to their impacts on flash floods, landslides and debris flows and potential for these to worsen with global warming. This has been led in a concerted international effort by the INTENSE Crosscutting Project of the GEWEX (Global Energy and Water Exchanges) Hydroclimatology Panel. Here, we summarize the main findings so far and suggest future directions for research, including: the benefits of convection-permitting climate modelling; towards understanding mechanisms of change; the usefulness of temperature-scaling relations; towards detecting and attributing extreme rainfall change; and the need for international coordination and collaboration. Evidence suggests that the intensity of long-duration (1 day+) heavy precipitation increases with climate warming close to the Clausius–Clapeyron (CC) rate (6–7% K −1 ), although large-scale circulation changes affect this response regionally. However, rare events can scale at higher rates, and localized heavy short-duration (hourly and sub-hourly) intensities can respond more strongly (e.g. 2 × CC instead of CC). Day-to-day scaling of short-duration intensities supports a higher scaling, with mechanisms proposed for this related to local-scale dynamics of convective storms, but its relevance to climate change is not clear. Uncertainty in changes to precipitation extremes remains and is influenced by many factors, including large-scale circulation, convective storm dynamics andstratification. Despite this, recent research has increased confidence in both the detectability and understanding of changes in various aspects of intense short-duration rainfall. To make further progress, the international coordination of datasets, model experiments and evaluations will be required, with consistent and standardized comparison methods and metrics, and recommendations are made for these frameworks. This article is part of a discussion meeting issue ‘Intensification of short-duration rainfall extremes and implications for flash flood risks’.

scholarly journals Challenges and outlook for convection-permitting climate modelling

2021 ◽  
Vol 379 (2195) ◽  
pp. 20190547 ◽  
Author(s):  
E. J. Kendon ◽  
A. F. Prein ◽  
C. A. Senior ◽  
A. Stirling
Keyword(s):  
Short Duration ◽  
Land Surface ◽  
Weather Forecasting ◽  
Flash Flood ◽  
Surface Fluxes ◽  
Extreme Weather Events ◽  
Small Scale ◽  
Climate Projections ◽  
Climate Modelling ◽  
Major Advance

Climate projections at very high resolution (kilometre-scale grid spacing) are becoming affordable. These ‘convection-permitting’ models (CPMs), commonly used for weather forecasting, better represent land-surface characteristics and small-scale processes in the atmosphere such as convection. They provide a step change in our understanding of future changes at local scales and for extreme weather events. For short-duration precipitation extremes, this includes capturing local storm feedbacks, which may modify future increases. Despite the major advance CPMs offer, there are still key challenges and outstanding science issues. Heavy rainfall tends to be too intense; there are challenges in representing land-surface processes; sub-kilometre scale processes still need to be parametrized, with existing parametrization schemes often requiring development for use in CPMs; CPMs rely on the quality of lateral boundary forcing and typically do not include ocean-coupling; large CPM ensembles that comprehensively sample future uncertainties are costly. Significant progress is expected over the next few years: scale-aware schemes may improve the representation of unresolved convective updrafts; work is underway to improve the modelling of complex land-surface fluxes; CPM ensemble experiments are underway and methods to synthesize this information with larger coarser-resolution model ensembles will lead to local-scale predictions with more comprehensive uncertainty context for user application. Large-domain (continental or tropics-wide) CPM climate simulations, potentially with additional earth-system processes such as ocean and wave coupling and terrestrial hydrology, are an exciting prospect, allowing not just improved representation of local processes but also of remote teleconnections. This article is part of a discussion meeting issue ‘Intensification of short-duration rainfall extremes and implications for flash flood risks’.

scholarly journals Flash floods: formation, study and distribution

2020 ◽  
Vol 163 ◽  
pp. 02005
Author(s):  
Liudmila Kuksina ◽  
Valentin Golosov
Keyword(s):  
Short Duration ◽  
Debris Flows ◽  
Flash Flood ◽  
Flash Floods ◽  
Mountain Areas ◽  
Antecedent Soil Moisture ◽  
Small Catchment ◽  
Natural Factors ◽  
Spatio Temporal ◽  
Equatorial Climate

Flash floods are one of the most widespread and dangerous phenomenon on our planet. They are characterized by fast speed of development and short duration. However their study just begins because there is no one opinion what flash flood is, and there is no special term in many countries. The key reasons of their formation are intensive rainfall of short duration, location of river basin in mountain areas, and small catchment area, providing fast concentration of the runoff in river channel. Another significant factor is antecedent soil moisture. Flash floods are mostly spread in zones of subtropic, tropic and equatorial climate in the northern hemisphere. The study of flash floods is implemented in various fields of science due to hydrometeorological and lythogeomorphological causes of their formation. The important task is the differentiation of flash floods and debris flows. It can be based on the relations between sediment yield and sediments grain size and runoff characteristics with a glance of sediments concentration. The scheme of natural factors of flash floods formation is suggested with their differentiation from debris flows and floods of other types. The main issues of flash floods research and forecast are connected with small spatio-temporal scale of phenomenon and remoteness of river basins.

Characterizing Dam Induced Flood at Downstream of a Hydel Project 

2021 ◽  
Author(s):  
Dipsikha Devi ◽  
Anupal Baruah ◽  
Arup Kumar Sarma
Keyword(s):  
Water Level ◽  
Short Duration ◽  
Flash Flood ◽  
Daily Basis ◽  
Low Flow ◽  
Mitigation Measures ◽  
Hydropower Project ◽  
River Bank ◽  
Operating Policy ◽  
The Impact

<p>Flooding due to sudden release from a hydropower dam during monsoon is becoming a serious concern for downstream locality, especially when there is lack of coordination between the dam authority and the Disaster Management Authority (DMA) at downstream. For hilly river, a disastrous flash flood is generally caused by short duration high intensity precipitation and a pondage hydropower project cannot attenuate such flood. Generally, reservoir simulation/optimization for a hydropower project is carried out on monthly, ten-daily or at best on daily basis to determine the best operating policy and to analyze impact of such operation on the flow scenario and therefore, in conventional analysis such flash flood event goes un-noticed. A detailed investigation of the downstream flooding is required before the construction of any hydropower project with at least on hourly basis to get insight into the impact of such inflow at downstream. Non-availability of short duration precipitation/flow data in interior project area, particularly in developing country hinder such analysis. Need and scope of such analysis is demonstrated by using a typical flow hydrograph of 48 hours, having two flood peaks, as inflow to the Lower Subansiri Hydroelectric Project (LSHP). The project is located in the Subansiri River, the largest tributary of the Brahmaputra River in India. Two operating policies; i) Standard Operating Policy (SOP) and ii) Dynamic Programming (DP) generated operating policy have been tested and both the polices have generated similar hourly flow time series of total reservoir outflow (spill + Release). These reservoir operation models have been coupled with the hydrodynamic model to route the hourly reservoir outflow from LSHP to a flood prone area located 13Km downstream of it. Post dam flood scenario thus generated is compared with the pre dam flood scenario by routing the same inflow hydrograph without considering the dam. As the river has an embankment, and flooding occurs only when the embankment fails, a specified water level at the downstream section has been considered as critical for flooding for the purpose of a comparative study.  For the considered inflow hydrograph, it is observed that the flood magnitude is not increased by the action of dam operation rather peaks get slightly attenuated. However, in natural condition without dam, flood rises gradually providing prior information to the locality and providing sufficient time for completing pre-disaster actions based on experience. With inclusion of dam, peak flow rises vary rapidly from a very low flow without showing any indication of flood beforehand and thus flood becomes more disastrous. Sudden fluctuation of water level can also cause failure of river bank and progressive bank failure can eventually cause the embankment to fail. The analysis has shown the possible impact of hydel project with more clarity to help disaster manager prepare mitigation measures in an informed way.</p>

scholarly journals Suitable Low Income Flood Resilient Housing

2015 ◽  
pp. 1-11
Author(s):  
Nachawit Tikul
Keyword(s):  
Climate Change ◽  
Flow Velocity ◽  
Short Duration ◽  
Low Income ◽  
Open Space ◽  
Flash Flood ◽  
Critical Issue ◽  
Flood Frequency ◽  
Slow Flow ◽  
Factors Affecting

Climate change is a critical issue for all of humanity. It is predicted that Thailand is likely to have an increasing frequency and intensity of rainfall and storms which, will result in a more severe flash flood problem. Slum residents in Chiang Mai are one of the groups of people who are vulnerable to flooding impacts of climate change. The objective of this study is to analyze the flood-resilient housing style of low-income people. Data from 3 slums (146 households) which encounter different kinds of floods every year, i.e. drainage floods (Ban Sanku: 21 households), river floods (Kampang Ngam: 64 households) and flash floods (Samunkee Pattana: 61 house- holds), were collected. The study found that flood frequency, duration, depth and flow velocity caused damage to the houses, but only flood frequency, duration, and flow velocity were factors affecting the housing structure. If considering only damage to slums which frequently face shallow water depth, slow flow velocity and short duration, all 8 low-income housing styles (A-H) can be built. The high platform house with open space under the house is appropriate for slums located in flooding area where high-level, slow flow velocit y floods occur frequently but for a short duration. It may be a permanent, semi-permanent or temporary structure (D-F). For the other slums facing high flood levels with high flow velocities for a short duration, all permanent housing styles are appropriate. If the objective is not only damage prevention but also living during a flood, per- manent high platform houses with open spaces under the houses are recommended for all slums.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

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