Installation of blue-green solutions at large scale to mitigate pluvial floods

2020 ◽  
Author(s):  
Elena Cristiano ◽  
Stefano Farris ◽  
Roberto Deidda ◽  
Francesco Viola
Keyword(s):  
Large Scale ◽  
Rainwater Harvesting ◽  
Scale Effects ◽  
Extreme Rainfall ◽  
Green Roofs ◽  
Added Value ◽  
Small Scale ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Harvesting Systems

<p><strong> </strong>The growth of urbanization and the intensification of extreme rainfall events, that has characterized the last century, are leading to an increase of pluvial floods, which are becoming a significant problem in many cities. Among the different solutions proposed and developed to mitigate flood risk in urban areas, green roofs and rainwater harvesting systems have been deeply investigated to reduce the runoff contribution generated from rooftops. These tools have been largely studied at small scale, analysing the flood reduction that can be achieved from one single building or in a small neighbourhood, without considering the large-scale effects. In this work, the potential impact of the installation of green-blue solutions on all the rooftops of a city is evaluated, assuming to place green roofs on flat roofs and rainwater harvesting systems on sloped ones. We investigated nine cities from 5 different countries (Canada, Haiti, United Kingdom, Italy and New Zealand), representing different climatological and geomorphological characteristics. The behaviour of the blue-green solution was estimated with the help of a conceptual lumped ecohydrological model and the mass conservation, using rainfall and temperature time series as climatological input to derive the discharge reduction for different scenarios. Due to the high percentage of sloped roofs in most of the investigated locations, the cost-efficiency analysis highlights that the large-scale installation of rainwater harvesting tanks enables to achieve higher mitigation capacity than green roofs at lower cost. Green roofs, however, present many additional benefits (such as biodiversity contribution, thermal insulation for buildings, pollution reduction and increase of aesthetic added value) that need to be evaluated by urban planners and policy makers. The best achievable performance is given by the coupled system of rainwater harvesting tanks and intensive green roofs: for extreme rainfall events this solution guarantees a discharge reduction up to 20% in most of the cities.</p>

scholarly journals Large scale and sub-regional connections in the lead up to summer heat wave and extreme rainfall events in eastern Australia

2014 ◽  
Vol 44 (7-8) ◽  
pp. 1823-1840 ◽  
Author(s):  
Ghyslaine Boschat ◽  
Alexandre Pezza ◽  
Ian Simmonds ◽  
Sarah Perkins ◽  
Tim Cowan ◽  
...  
Keyword(s):  
Heat Wave ◽  
Large Scale ◽  
Extreme Rainfall ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Summer Heat ◽  
Eastern Australia

scholarly journals ­Trends and Zonal Variability of Extreme Rainfall Events Over East Africa During 1960-2017

2021 ◽  
Author(s):  
Moses.A Ojara ◽  
Yunsheng Lou ◽  
Hasssen Babaousmail ◽  
Peter Wasswa
Keyword(s):  
Extreme Events ◽  
Heavy Rainfall ◽  
Rainwater Harvesting ◽  
Southern Oscillation ◽  
Extreme Rainfall ◽  
Mitigation Measures ◽  
Fluctuation Analysis ◽  
Positive Trend ◽  
Extreme Rainfall Events ◽  
Rainfall Events

Abstract East African countries (Uganda, Kenya, Tanzania, Rwanda, and Burundi) are prone to weather extreme events. In this regard; the past occurrence of extreme rainfall events is analyzed for 25 stations following the Expert Team on Climate Change Detection and Indices (ETCCDI) regression method. Detrended Fluctuation Analysis (DFA) is used to show the future development of extreme events. Pearson’s correlation analysis is performed to show the relationship of extreme events between different rainfall zones and their association with El Niño -Southern Oscillation (ENSO and Indian Ocean dipole (IOD) IOD-DMI indices. Results revealed that the consecutive wet day's index (CWD) was decreasing trend in 72% of the stations analyzed, moreover consecutive dry days (CDD) index also indicated a positive trend in 44% of the stations analyzed. Heavy rainfall days index (R10mm) showed a positive trend at 52% of the stations and was statistically significant at a few stations. In light of the extremely heavy rainfall days (R25mm) index, 56% of the stations revealed a decreasing trend for the index and statistically significant trend at some stations. Further, a low correlation coefficient of extreme rainfall events in the regions; and between rainfall extreme indices with the atmospheric teleconnection indices (Dipole Mode Index-DMI and Nino 3.4) (r = -0.1 to r = 0.35). Most rainfall zones showed a positive correlation between the R95p index and DMI, while 5/8 of the rainfall zones experienced a negative correlation between Nino 3.4 index and the R95p. In light of the highly variable trends of extremes events, we recommend planning adaptation and mitigation measures that consider the occurrence of such high variability. Measures such as rainwater harvesting, stored and used during needs, planned settlement, and improved drainage systems management supported by accurate climate and weather forecasts is highly advised.

Hydro-geomorphological response to changes in the spatial structure of extreme rainfall in a warmer world

2020 ◽  
Author(s):  
Nadav Peleg ◽  
Chris Skinner ◽  
Simone Fatichi ◽  
Peter Molnar
Keyword(s):  
Sediment Transport ◽  
Spatial Structure ◽  
Extreme Rainfall ◽  
Climate Impacts ◽  
Small Scale ◽  
Runoff Generation ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Sediment Yields ◽  
Rainfall Volume

<p>Spatial characteristics of extreme rainfall are expected to change with increasing temperatures. Extreme rainfall directly affects streamflow and sediment transport volumes and peaks, yet the effect of climate change on the small-scale spatial structure of extreme rainfall and subsequent impacts on hydrology and geomorphology remain largely unexplored. Motivated by this knowledge gap, we conducted a numerical experiment in which synthetic rainfall fields representing extreme rainfall events of two types, stratiform and convective, were simulated using a space-time rainfall generator model (AWE-GEN-2d). The rainfall fields were modified to follow different spatial rainfall scenarios, associated with increasing temperatures, and used as inputs into a landscape evolution model (CAESAR-Lisflood). We found that the response of the streamflow and sediment yields are highly sensitive to changes in total rainfall volume and to a lesser extent to changes in localized peak rainfall intensities. The morphological (erosion and sediment transport) components were found to be more sensitive to changes in rainfall spatial structure in comparison to the hydrological components, and more sensitive to convective rainfall than stratiform rainfall because of localized runoff generation and erosion production. In addition, we showed that assuming extreme rainfall events to intensify with increasing temperatures without introducing a change in the rainfall spatial structure might lead to over-estimation of future climate impacts on basin-wide hydro-geomorphology.</p>

scholarly journals Impacts of the Madden-Julian Oscillation (MJO) on rainfall in Sri Lanka

MAUSAM ◽  
2021 ◽  
Vol 71 (3) ◽  
pp. 405-422
Author(s):  
JAYAWARDENA I M SHIROMANI PRIYANTHIKA ◽  
WHEELER MATTHEW C ◽  
SUMATHIPALA W L ◽  
BASNAYAKE B R S B
Keyword(s):  
Sri Lanka ◽  
Large Scale ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Southwest Monsoon ◽  
Boreal Winter ◽  
Northeast Monsoon ◽  
Madden Julian Oscillation ◽  
Extreme Rainfall Events ◽  
Rainfall Events

The influence of the Madden Julian Oscillation (MJO) on rainfall in Sri Lanka (SL) is examined based on 30 years of daily station data from 1981-2010. Composites are constructed for each of the eight phases of the MJO defined with the Real-time Multivariate MJO (RMM) index, using daily rainfall data from 44 stations over SL for four climatic seasons and comparing to similar results from a satellite-based rainfall product. Composites of lower tropospheric wind and convective anomaly are also investigated in order to examine how the local rainfall anomalies are associated with large-scale circulations. The greatest impact of the MJO on rainfall over SL occurs in the Second Inter-Monsoon (SIM) and Southwest Monsoon (SWM) seasons. Enhanced rainfall generally occurs over SL during RMM phases 2 and 3 when the MJO convective envelop is located in the Indian Ocean and conversely suppressed rainfall in phases 6 and 7. This rainfall impact is due to the direct influence of the MJO’s tropical convective anomalies and associated low-level circulations in the vicinity of SL. In contrast, the MJO influence during the Northeast Monsoon (NEM) season is slightly less than during the SWM and SIM seasons as a result of the southward shift of the MJO convective envelop during boreal winter. Occurrence of extreme rainfall events is most frequent during phase 2 in First Inter-Monsoon (FIM) phases 2 and 3 in SWM, phases 1, 2 and 3 in SIM and phases 2 and 3 in NEM seasons. The analysis of this study provides a useful reference of when and where the MJO has significant impacts on rainfall as well as extreme rainfall events during four climatic seasons in SL. This information can be used along with accurately predicted MJO phase by dynamical or statistical models, to improve extended range forecasting in SL.

scholarly journals Cross–Time Scale Interactions and Rainfall Extreme Events in Southeastern South America for the Austral Summer. Part I: Potential Predictors

2015 ◽  
Vol 28 (19) ◽  
pp. 7894-7913 ◽  
Author(s):  
Á. G. Muñoz ◽  
L. Goddard ◽  
A. W. Robertson ◽  
Y. Kushnir ◽  
W. Baethgen
Keyword(s):  
South America ◽  
Extreme Events ◽  
Time Scale ◽  
Large Scale ◽  
Extreme Rainfall ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Rainfall Extreme ◽  
Moisture Advection ◽  
Basic Set

Abstract The physical mechanisms and predictability associated with extreme daily rainfall in southeastern South America (SESA) are investigated for the December–February season in a two-part study. Through a k-mean analysis, this first paper identifies a robust set of daily circulation regimes that are used to link the frequency of rainfall extreme events with large-scale potential predictors at subseasonal-to-seasonal scales. This represents a basic set of daily circulation regimes related to the continental and oceanic phases of the South Atlantic convergence zone (SACZ) and wave train patterns superimposed on the Southern Hemisphere polar jet. Some of these recurrent synoptic circulation types are conducive to extreme rainfall events in the region through synoptic control of different mesoscale physical features and, at the same time, are influenced by climate phenomena that could be used as sources of potential predictability. Extremely high rainfall (as measured by the 95th and 99th percentiles) is associated with two of these weather types (WTs), which are characterized by moisture advection intrusions from lower latitudes and the Pacific Ocean; another three WTs, characterized by above-normal moisture advection toward lower latitudes or the Andes, are associated with dry days (days with no rain). The analysis permits the identification of several subseasonal-to-seasonal scale potential predictors that modulate the occurrence of circulation regimes conducive to extreme rainfall events in SESA. It is conjectured that a cross–time scale interaction between the different climate drivers improves the predictive skill of extreme precipitation in the region.

scholarly journals Documentary evidence of historical floods and extreme rainfall events in Sweden 1400–1800

2015 ◽  
Vol 19 (3) ◽  
pp. 1307-1323 ◽  
Author(s):  
D. Retsö
Keyword(s):  
Large Scale ◽  
18Th Century ◽  
Climatic Factors ◽  
Extreme Rainfall ◽  
Flood Frequency ◽  
Ice Age ◽  
Documentary Evidence ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Atmospheric Circulation Patterns

Abstract. This article explores documentary evidence of floods and extreme rainfall events in Sweden in the pre-instrumental period (1400–1800). The survey shows that two sub-periods can be considered as flood-rich, 1590–1670 and the early 18th century. The result related to a low degree of human impact on hydrology during the period, suggests that climatic factors, such as lower temperatures and increased precipitation connected to the so-called Little Ice Age rather than large-scale atmospheric circulation patterns, should be considered as the main driver behind flood frequency and magnitude.

scholarly journals Large-Scale Environmental Conditions Related to Midsummer Extreme Rainfall Events around Japan in the TRMM Region

2018 ◽  
Vol 31 (17) ◽  
pp. 6933-6945 ◽  
Author(s):  
Atsushi Hamada ◽  
Yukari N. Takayabu
Keyword(s):  
Extreme Events ◽  
Environmental Conditions ◽  
Large Scale ◽  
Southern China ◽  
Extreme Rainfall ◽  
Extreme Rainfall Events ◽  
Near Surface ◽  
Rainfall Events ◽  
Precipitation Characteristics ◽  
Large Scale Flow

The precipitation characteristics of extreme events in August determined from 13 years of satellite data around Japan in the TRMM observation region and their relationship with large-scale environmental conditions are examined. Two types of extreme events, extreme rainfall and extreme convective events, are defined in each analysis grid box using maximum near-surface rainfall and maximum 40-dB Z echo-top height in each event, respectively. There are clear differences in precipitation characteristics between the two types of extreme events. Extreme rainfall events are more organized precipitation systems than the extreme convective events, with relatively lower echo-top heights and very low lightning activity. There are also clear differences in the related environmental conditions, where the environments related to the extreme rainfall events are somewhat convectively stable and very humid in almost the entire troposphere. These facts are consistent with our previous studies and reinforce the importance of warm-rain processes in extremely intense precipitation productions. The environments related to the extreme rainfall events exhibit a zonally extended moist anomaly in the free troposphere from southern China to the east of Japan, indicating that the excessive moisture transported from the west by a large-scale flow may partially play a role in producing environmental conditions favorable for extreme rainfall. On the other hand, the environments related to extreme convective events are not associated with free-tropospheric moisture inflow. The relationships with the tropical cyclones and upper-tropospheric dynamical fields are also examined, and are found to be clearly different between the extreme rainfall events and extreme convective events.

Dominant large-scale parameters responsible for diverse extreme rainfall events over vulnerable Odisha state in India

2019 ◽  
Vol 53 (11) ◽  
pp. 6629-6644 ◽  
Author(s):  
Madhusmita Swain ◽  
P. Sinha ◽  
U. C. Mohanty ◽  
S. Pattnaik
Keyword(s):  
Large Scale ◽  
Extreme Rainfall ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Scale Parameters

scholarly journals Comparison of blue-green solutions for urban flood mitigation: A multi-city large-scale analysis

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0246429
Author(s):  
Elena Cristiano ◽  
Stefano Farris ◽  
Roberto Deidda ◽  
Francesco Viola
Keyword(s):  
Large Scale ◽  
Rainwater Harvesting ◽  
Green Roofs ◽  
Mitigation Measures ◽  
Surface Discharge ◽  
Economic Losses ◽  
Retention Capacity ◽  
Local Climate ◽  
Financial Investment ◽  
Harvesting Systems

Flooding risk in cities has been recently exacerbated by increased urbanization and climate change, often with catastrophic consequences in terms of casualties and economic losses. Rainwater harvesting systems and green roofs are recognized as being among the most effective blue-green mitigation measures. However, performances of these systems have currently been investigated only at laboratory or very-small local scales. In this work, we assess the potential benefit of the extensive installation of these solutions on all the rooftops of 9 cities, with different climatological and geographical characteristics. Both surface discharge reduction and delay between rainfall and runoff peak generation have been investigated. Green roofs ensure a larger average lag time between rainfall and runoff peaks than rainwater harvesting systems, without significant differences between intensive and extensive structures. On the other hand, the cost-efficiency analysis, considering the entire urban area, shows a higher retention capacity with a lower financial investment for rainwater harvesting rather than for green roofs in most cases. For extreme rainfall events, large-scale installation of rainwater harvesting systems coupled with intensive green roofs over the entire city have shown to be the most efficient solution, with a total discharge reduction that can vary from 5% to 15%, depending on the city characteristics and local climate.

scholarly journals Finding Cost-Effective Solutions for Climate Change Adaptation in Bergen Using Extensive Climate, Economic and Spatial Data

10.29007/p6x3 ◽  
2018 ◽  
Author(s):  
Clemens Strehl ◽  
Erle Kristvik ◽  
Juliane Koti
Keyword(s):  
Climate Change ◽  
Spatial Data ◽  
Green Infrastructure ◽  
Extreme Rainfall ◽  
Cost Effective ◽  
Green Roofs ◽  
Data Availability ◽  
Combined Sewer Overflows ◽  
Extreme Rainfall Events ◽  
Rainfall Events

The adaptation of urban water systems to climate change is a complex management challenge. Especially urban drainage systems and their adaptation to growing climate change dynamics, like increasing variations in terms of intensity and frequency of heavy rainfall events, calls for novel adaptation approaches. Growing data availability opens the chance to find suitable cost-effective solutions to tackle climate change risks. In the Damsgård area in Bergen, combined sewer overflows discharge in the fjord during extreme rainfall events. Within the European project BINGO, an evaluation of alternative ways to reduce this environmental pressure is being conducted, using extensive climate, economic and spatial data. The analysis is going to compare different combinations of green infrastructure from the field of water sensitive urban design, like green roofs, ditches and swales. These combinations are furthermore compared with an innovative approach: using the slope of roads as emergency flood water ways.

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