Nature-based solutions for hydro-meteorological risk reduction: a state-of-the-art review of the research area

Nature-based solutions for hydro-meteorological risk reduction: a state-of-the-art review of the research area
Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Nature-based solutions for hydro-meteorological risk reduction:
a state-of-the-art review of the research area
Laddaporn Ruangpan1,2 , Zoran Vojinovic1,3 , Silvana Di Sabatino4 , Laura Sandra Leo4 , Vittoria Capobianco5 ,
Amy M. P. Oen5 , Michael E. McClain1,2 , and Elena Lopez-Gunn6
1 IHE  Delft Institute for Water Education, Delft, the Netherlands
2 Department    of Water Management, Faculty of Civil Engineering and Geosciences,
Delft University of Technology, Delft, the Netherlands
3 College for Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
4 Department of Physics and Astronomy, University of Bologna, Bologna, Italy
5 Norwegian Geotechnical Institute, Oslo, Norway
6 Icatalist S.L., Madrid, Spain

Correspondence: Laddaporn Ruangpan (

Received: 16 April 2019 – Discussion started: 30 April 2019
Revised: 29 November 2019 – Accepted: 15 December 2019 – Published: 20 January 2020

Abstract. Hydro-meteorological risks due to natural hazards       ing and replication and to make them become mainstream
such as severe floods, storm surges, landslides and droughts      solutions.
are causing impacts on different sectors of society. Such risks
are expected to become worse given projected changes in
climate, degradation of ecosystems, population growth and         1   Introduction
urbanisation. In this respect, nature-based solutions (NBSs)
have emerged as effective means to respond to such chal-          There is increasing evidence that climate change and asso-
lenges. A NBS is a term used for innovative solutions that are    ciated hydro-meteorological risk are already causing wide-
based on natural processes and ecosystems to solve different      ranging impacts on the global economy, human well-being
types of societal and environmental challenges. The present       and the environment. Floods, storm surges, landslides,
paper provides a critical review of the literature concerning     avalanches, hail, windstorms, droughts, heat waves and for-
NBSs for hydro-meteorological risk reduction and identifies       est fires are a few examples of hydro-meteorological hazards
current knowledge gaps and future research prospects. There       that pose a significant risk. Hydro-meteorological risk is the
has been a considerable growth of scientific publications on      probability of damage due to hydro-meteorological hazards
this topic, with a more significant rise taking place from 2007   and its interplay with exposure and vulnerability of the af-
onwards. Hence, the review process presented in this paper        fected humans and environments (Merz et al., 2010). Some
starts by sourcing 1608 articles from Scopus and 1431 ar-         of the main reasons for such risks are climate change, land
ticles from the Web of Science. The full analysis was per-        use change, water use change and other pressures linked to
formed on 146 articles. The analysis confirmed that numer-        population growth (Thorslund et al., 2017). The situation is
ous advancements in the area of NBSs have been achieved to        likely to become worse given the projected changes in cli-
date. These solutions have already proven to be valuable in       mate (see, for example, EEA, 2017). Therefore, effective
providing sustainable, cost-effective, multi-purpose and flex-    climate change adaptation (CCA) and disaster risk reduc-
ible means for hydro-meteorological risk reduction. How-          tion (DRR) strategies are needed to mitigate the risks of ex-
ever, there are still many areas where further research and       treme events and to increase resilience to disasters, particu-
demonstration are needed in order to promote their upscal-        larly among vulnerable populations (Maragno et al., 2018;
                                                                  McVittie et al., 2018).

Published by Copernicus Publications on behalf of the European Geosciences Union.
Nature-based solutions for hydro-meteorological risk reduction: a state-of-the-art review of the research area
244                                   L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction

   Since biodiversity and ecosystem services can play an im-      2   Overview of definitions and theoretical backgrounds
portant role in responding to climate-related challenges, both
mitigation and adaptation strategies should take into consid-     There are several terms and concepts which have been used
eration a variety of green infrastructure (GI) and ecosystem-     interchangeably in the literature to date. In terms of the
based adaptation (EbA) measures as effective means to re-         NBSs, the two most prominent definitions are from the Inter-
spond to present and future disaster risk (see also EEA,          national Union for Conservation of Nature (IUCN) and the
2015). Such approaches are already well accepted within           European Commission. The European Commission defines
multilateral frameworks such as the United Nations (UN)           nature-based solutions as “Solutions that aim to help soci-
Framework Convention on Climate Change (UNFCCC), the              eties address a variety of environmental, social and economic
Convention on Biological Diversity (CBD) and the Sendai           challenges in sustainable ways. They are actions inspired by,
Framework for Disaster Risk Reduction (SFDRR). As such,           supported by or copied from nature, both using and enhanc-
they are recognised as effective means for CCA and DRR            ing existing solutions to challenges as well as exploring more
and for the implementation of the Sustainable Development         novel solutions. Nature-based solutions use the features and
Goals (SDGs).                                                     complex system processes of nature, such as its ability to
   In view of the points above, many countries are nowa-          store carbon and regulate water flows, in order to achieve de-
days developing adaptation and mitigation strategies based        sired outcomes, such as reduced disaster risk and an environ-
on GI and EbA to reduce their vulnerability to hydro-             ment that improves human well-being and socially inclusive
meteorological hazards (Rangarajan et al., 2015; EEA,             green growth” (EC, 2015). The IUCN has proposed a defini-
2015). Nature-based solutions (NBSs) have been introduced         tion of NBSs as “actions to protect, sustainably manage and
relatively recently. The reason for their introduction is that    restore natural and modified ecosystems that address societal
NBSs offer the possibility to work closely with nature in         challenges effectively and adaptively, simultaneously pro-
adapting to future changes, reducing the impact of climate        viding human well-being and biodiversity benefits” (Cohen-
change and improving human well-being (Cohen-Shacham              Shacham et al., 2016). Eggermont et al. (2015) proposed a
et al., 2016). NBSs have been the focus of research in sev-       typology characterising NBSs into three types: (i) NBSs that
eral EU Horizon 2020-funded projects. Horizon 2020 offers         address a better use of natural or protected ecosystems (no or
new opportunities in the focus area of “Smart and Sustain-        minimal intervention), which fits with how the IUCN frames
able Cities with Nature based solutions” (Faivre et al., 2017).   NBSs, (ii) NBSs for sustainability and multi-functionality of
Some of these important projects are Nature4Cites, NATUR-         managed ecosystems, and (iii) NBSs for the design and the
VATION, NAIAD, BiodivERsA, INSPIRATION, URBAN                     management of new ecosystems, which is more representa-
GreenUP, UNaLaB, URBINAT, CLEVER Cities, proGIreg,                tive of the definition given by the European Commission.
EdiCitNet, Regenerating ECOsystems with Nature-based                  A NBS is a collective term for innovative solutions to
solutions for hydro-meteorological risk rEduCTion (RE-            solve different types of societal and environmental chal-
CONECT), OPERANDUM, ThinkNature, EKLIPSE and                      lenges, based on natural processes and ecosystems. There-
PHUSICOS (nature4cities, 2019). Through these projects,           fore, it is considered to be an “umbrella concept” cover-
knowledge of NBSs has grown rapidly and been documented           ing a range of different ecosystem-related approaches and
in a considerable body of grey literature (project reports, for   linked concepts (Cohen-Shacham et al., 2016; Nesshöver et
example). On the other hand, the number of scientific stud-       al., 2017) that provides an integrated way to look at differ-
ies focused on NBSs to reduce hydro-meteorological risk is        ent issues simultaneously. Due to the diverse policy origins,
continuously increasing all over the world.                       NBS terminology has evolved in the literature to emphasise
   The aim of this article is to provide a state-of-the-art re-   different aspects of natural processes or functions. In this re-
view of scientific publications on hydro-meteorological risk      gard, nine different terms are commonly used in the scien-
reduction with NBSs to indicate some directions for future        tific literature in the context of hydro-meteorological risk re-
research based on the current knowledge gaps. The analy-          duction: low-impact developments (LIDs), best management
sis focuses on the following hydro-meteorological hazards:        practices (BMPs), water-sensitive urban design (WSUD),
floods, droughts, storm surges and landslides. The review         sustainable urban drainage systems (SuDs), green infrastruc-
addresses both small- and large-scale interventions and ex-       ture (GI), blue–green infrastructure (BGI), ecosystem-based
plores available techniques, methods and tools for NBS as-        adaptation (EbA) and ecosystem-based disaster risk reduc-
sessment while also providing a snapshot of the major socio-      tion (Eco-DRR). The timeline of each term based on their
economic factors at play in the implementation process. The       appearance in literature is shown in Fig. 1, and their defini-
key objectives and methods of this study are discussed in         tions are given in Table 1.
Sect. 3, while Sect. 2 provides a brief overview of concepts
and definitions related to NBSs either in general or that are
specifically linked to hydro-meteorological risk reduction.
Results and conclusions are discussed in Sects. 4 and 5 re-

Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020                 
Nature-based solutions for hydro-meteorological risk reduction: a state-of-the-art review of the research area
L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction                                                                       245

Figure 1. Timeline and year of origin of each term (low-impact developments – LIDs, best management practices – BMPs, water-sensitive ur-
ban design – WSUD, green infrastructure – GI, sustainable urban drainage systems – SuDs, nature-based solutions – NBSs, ecosystem-based
adaptation – EbA, ecosystem-based disaster risk reduction – Eco-DRR – and blue–green infrastructure – BGI) based on their appearance in

Table 1. Glossary of terms and their geographical usage.

  Terminology               Definition, objectives and purpose                                              Places where commonly used   Reference

  Low-impact                “LID is used as a retro- fit designed to reduce the stress on urban             – US                         Eckart et al.
  development (LIDs)        stormwater infrastructure and/or create the resiliency to adapt to climate      – New Zealand                (2017)
                            changes, LID relies heavily on infiltration and evapotranspiration and
                            attempts to incorporate natural features into design.”
  Best management           “A device, practice or method for removing, reducing, retarding or              – US                         Strecker et
  practices (BMPs)          preventing targeted stormwater run-off constituents, pollutants and             – Canada                     al. (2001)
                            contaminants from reaching receiving waters.”
  Water-sensitive           “Manage the water balance, maintain and where possible enhance water            – Australia                  Whelans
  urban design              quality, encourage water conservation and maintain water-related                                             consultants et
  (WSUD)                    environmental and recreational opportunities.”                                                               al. (1994)
  Sustainable urban         “Replicate the natural drainage processes of an area – typically through        – UK                         Ossa-Moreno
  drainage systems          the use of vegetation-based interventions such as swales, water gardens                                      et al.
  (SuDs)                    and green roofs, which increase localised infiltration, attenuation and/or                                   (2017)
                            detention of stormwater.”
  Green infrastructure      “The network of natural and semi-natural areas, features and green              – US                         Naumann et
  (GI)                      spaces in rural and urban, and terrestrial, freshwater, coastal and marine      – UK                         al. (2011)
                            areas, which together enhance ecosystem health and resilience, contribute
                            to biodiversity conservation and benefit human populations through the
                            maintenance and enhancement of ecosystem services.”
  Ecosystem-based           “The use of biodiversity and ecosystem services as part of an overall           – Canada                     CBD (2009)
  adaptation (EbA)          adaptation strategy to help people to adapt to the adverse effects of climate   – Europe
  Ecosystem-based           “The sustainable management, conservation, and restoration of                   – Europe                     Estrella and
  disaster risk reduction   ecosystems to reduce disaster risk, with the aim of achieving sustainable       – US                         Saalismaa
  (Eco-DRR)                 and resilient development.”                                                                                  (2013)
  Blue–green                “BGI provides a range of services that include; water supply, climate           – UK                         Lawson et
  infrastructure (BGI)      regulation, pollution control and hazard regulation (blue services/goods),                                   al. (2014)
                            crops, food and timber, wild species diversity, detoxification, cultural
                            services (physical health, aesthetics, spiritual), plus abilities to adapt to
                            and mitigate climate change.”
  Nature-based              “NBS aim to help societies address a variety of environmental, social and       – Europe                     EC (2015)
  solution                  economic challenges in sustainable ways. They are actions inspired by,
                            supported by or copied from nature, both using and enhancing existing
                            solutions to challenges as well as exploring more novel solutions.”                                                 Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020
Nature-based solutions for hydro-meteorological risk reduction: a state-of-the-art review of the research area
246                                   L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction

    The commonalities between a NBS and its sister concepts       (EKLIPSE, 2017). Lafortezza et al. (2018) reviewed differ-
(i.e. GI, BGI, EbA and Eco-DRR) are that they take partic-        ent case studies around the world where NBSs have been
ipatory, holistic, integrated approaches, using nature to en-     applied from the micro scale to the macro scale. Further-
hance adaptive capacity, reduce hydro-meteorological risk,        more, an overview of how different NBS measures can reg-
increase resilience, improve water quality, increase the op-      ulate ecosystem services (i.e. soil protection, water quality,
portunities for recreation, improve human well-being and          flood regulation and water provision) has been carried out by
health, enhance vegetation growth, and connect habitat and        Keesstra et al. (2018).
biodiversity. More information on the history, scope, applica-
tion and underlying principle of terms of SuDs, LIDs, BMPs,
WSUD and GI can be found in Fletcher et al. (2015), while
the relationship between a NBS, GI–BGI and EbA is de-             3     Materials and methodology
scribed in detail by Nesshöver et al. (2017).
    Although all terms are based on a common idea, which          The methodology consisted of two phases as schematised in
is embedded in the umbrella concept of NBSs, differences          Fig. 2. The first phase consisted of the identification of arti-
in definition reflect their historical perspectives and knowl-    cles satisfying the search criteria discussed in Sect. 3.1. Next,
edge base that were relevant at the time of the research          all articles were screened and filtered based on the selection
(Fletcher et al., 2015). The distinguishing characteristic be-    criteria discussed in Sect. 3.2.
tween a NBS and its sister concepts is how they address so-
cial, economic and environmental challenges (Faivre et al.,       3.1    Search strategy
2018). Some terms such as SuDs, LIDs and WSUD refer
to NBSs that specifically address stormwater management.          The review analysis concerned articles from scientific jour-
They use the landscape feature to transform the linear ap-        nals written in English. Two main concepts were used in the
proach of conventional stormwater management into a more          search: nature-based solutions and hydro-meteorological risk
cyclic approach where drainage, water supply and ecosys-          reduction. As the concept of nature-based solutions appears
tems are treated as part of the same system, mimicking more       under different names (which more or less relate to the same
natural water flows (Liu and Jensen, 2018). GI and BGI focus      field of research), articles related to LIDs, BMPs, WSUD,
more on technology-based infrastructures by applying natu-        SuDs, GI, BGI, EbA and Eco-DRR were included in the
ral alternatives (Nesshöver et al., 2017) for solving a spe-      identification of relevant articles (see Table 2) The review
cific activity (i.e. urban planning or stormwater). EbA looks     of hydro-meteorological risk included literature on relevant
at long-term changes within the conservation of biodiversity,     terms (i.e. disasters, risks, hydrology, etc.) and different types
ecosystem services and climate change, while Eco-DRR is           of hazards (floods, droughts, storm surges and landslides; Ta-
more focused on immediate and medium-term impacts from            ble 2).
the risk of weather, climate and non-climate-related hazards.        During the construction of the queries, the strings were
EbA is often seen as a subset of NBSs that is explicitly con-     searched only within index terms and metadata “titles, ab-
cerned with climate change adaptation through the use of na-      stract, and keywords” in the Scopus database. The search
ture (Kabisch et al., 2016). From the above discussion, it can    terms for the two concepts were linked with the Boolean op-
be concluded that EbA, Eco-DRR and GI–BGI provide more            erator “AND”, while the Boolean operator “OR” was used
specific solutions to more specific issues. One key distinc-      to link possible terms (Table 2). An example of a protocol is
tion is that unlike the sister concepts, the concept of NBSs      shown below:
is more open to different interpretations, which can be use-         “TITLE-ABS-KEY (“Nature-based Solutions” OR “Na-
ful in encouraging stakeholders to take part in the discussion.   ture based solutions” OR “Nature Based Solutions” OR
Moreover, features of NBSs provide an alternative to work-        “nature-based solutions” OR “Low impact development” OR
ing with existing measures or grey infrastructures. Therefore,    “Sustainable Urban Drainage Systems” OR “Water Sensi-
it is important to note that very often a combination between     tive Urban Design” OR “Best Management Practices” OR
natural and traditional engineering solutions (also known as      “Green infrastructure” OR “Green blue infrastructure” AND
“hybrid” solutions) is likely to produce more effective results   “flood”) AND (LIMIT-TO (DOCTYPE, “ar”) OR LIMIT-
than any of these measures alone, especially when their co-       TO (DOCTYPE, “ch”) OR LIMIT-TO (DOCTYPE, “re”)
benefits are taken into consideration (Alves et al., 2019).       OR LIMIT-TO (DOCTYPE, “bk”)) AND (LIMIT-TO (LAN-
    An important advancement in the science and practice          GUAGE, “English”))”.
of NBSs is given by the EKLIPSE Expert Working Group,                The time window selected for the review process was
which developed the first version of a multi-dimensional im-      from 1 January 2007 to 19 November 2019; 1608 arti-
pact evaluation framework to support planning and evalua-         cles published in scientific journals were found in the Sco-
tion of NBS projects. The document includes a list of im-         pus database, and 1431 were found in the Web of Science
pacts, indicators and methods for assessing the performance       database. The articles from both databases were combined
of NBSs in dealing with some major societal challenges            for a total of 3089 articles. Duplicate articles were removed,

Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020                  
Nature-based solutions for hydro-meteorological risk reduction: a state-of-the-art review of the research area
L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction                                                    247

Figure 2. Process of article selection with systematic review method on nature-based solutions for hydro-meteorological risk reduction. The
final number of fully reviewed articles is 146.

resulting in a total of 1439 articles to be considered for fur-           2. to review the use of techniques, methods and tools for
ther evaluation.                                                             planning, selecting, evaluating and implementing NBSs
                                                                             for hydro-meteorological risk reduction;
3.2   Selection process
                                                                          3. to review the socio-economic influence in the imple-
As stated in the Introduction, this study aims at reviewing                  mentation of NBSs for hydro-meteorological risk re-
the state of the art of the research on NBSs that specifically               duction as well as their multiple benefits, co-benefits,
address hydro-meteorological risk reduction. In this regard,                 effectiveness and costs;
the key objectives of the present review work were carefully
formulated as follows:                                                    4. to identify trends, knowledge gaps and proposed future
                                                                             research prospects with respect to the above three ob-
  1. to assess the state of the art in research concerning both              jectives.
     small- and large-scale NBSs for hydro-meteorological
     risk reduction;                                   Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020
Nature-based solutions for hydro-meteorological risk reduction: a state-of-the-art review of the research area
248                                      L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction

Table 2. Selected concepts and terms used to search relevant literature on NBSs for hydro-meteorological risk reduction.

                    No.                                          Research words
                           First concept                                    Connection     Second concept
                           (nature-based solutions)                                        (hydro-meteorological risk)
                    1      “Nature-based solutions” OR                          AND        “Flood”
                    2      “Nature-Based Solutions” OR                          AND        “Drought”
                    3      “Low impact development” OR                          AND        “Storm surge”
                    4      “Sustainable Urban Drainage Systems” OR              AND        “Landslide”
                    5      “Water Sensitive Urban Design” OR                    AND        “Hydro-meteorological”
                    6      “Best Management Practices” OR                       AND        “Disaster”
                    7      “Green infrastructure” OR                            AND        “Review”
                    8      “Green blue infrastructure” OR                       AND        “Hydrology”
                    9      “Ecosystem-based Adaptation ” OR                     AND        “Coastal”
                    10     “Ecosystem-based disaster risk reduction” OR         AND        “Risk”
                    11     “Green and grey infrastructure”

These key objectives were defined for the review, with the              at the urban or local scale (i.e. buildings, streets, roofs or
intention that the results could be both quantitative and qual-         houses), while NBSs in rural areas, river basins and at the
itative.                                                                regional scale are referred to as large-scale NBSs (Fig. 3).
   The 1439 articles resulting from the search query were
thus evaluated with respect to these objectives and those               4.1.1   Research on small-scale NBSs for
found of little or no relevance with the topic removed.                         hydro-meteorological risk reduction
This selection process involved a set of progressive steps
as schematised in Fig. 2. Initially, all articles were analysed         Small-scale NBSs are usually applied to a specific location
on the basis of reading titles and keywords and evaluating              such as a single building or a street. However, for some
their relation to the search terms. Articles were discarded if          cases, a single NBS is not sufficient to control a large amount
their title and keywords were considered to be of little or no          of run-off. Therefore, this review discusses the application
relevance to the key objectives. This step served to reduce             and effectiveness of both individual NBSs and multiple-NBS
the number of articles from 1439 to 433. Secondly, a more               combinations. There are 41 articles that have been reviewed
in-depth analysis was conducted, based on reading the ab-               on the effectiveness of small-scale NBSs (Table 3). A major-
stract of each article selected in the previous step. The cri-          ity of these (31 articles) discuss the effectiveness of a single
teria at this step was that the abstract should discuss hydro-          or individual NBS site, while only 13 articles discuss the ef-
meteorological risk reduction. For example, if the abstract             fectiveness of multiple-NBS sites (around 31 %). A summary
focused more on water quality than risk, that paper was ex-             of the effectiveness, co-benefits and cost of NBS measures at
cluded. This step served to reduce the number of articles               small scale is shown in Table 3.
from 433 to 205. Finally, articles were read in full to iden-              To date, various types of single-NBS sites have been stud-
tify those that were relevant to the review objectives. Any             ied with objectives such as reduction of the flood peak (Car-
studies appearing to meet the key objectives (dealing with              penter and Kaluvakolanu, 2011; Ercolani et al., 2018; Liao et
subjects such as effectiveness of NBSs, techniques, method              al., 2015; Mei et al., 2018; Yang et al., 2018), delay and at-
and tools for planning, and other subjects relevant to the key          tenuation of the flood peak (Ishimatsu et al., 2017), reduction
objectives) were included in the review. As a result, the entire        of volume of combined sewer overflows (Burszta-Adamiak
selection process resulted in a total of 146 articles relevant to       and Mrowiec, 2013), and reduction of surface run-off volume
the objectives of the present review.                                   (Lee et al., 2013; Shafique and Kim, 2018). The review found
                                                                        just three articles that discuss the reduction of drought risk
                                                                        by using NBSs. Lottering et al. (2015) used NBSs to reduce
4     Findings                                                          water consumption in suburban areas, while Radonic (2019)
                                                                        showed that rainwater harvesting can help reduce household
4.1    Lesson from research on small- and large-scale                   water consumption. Finally, Wang et al. (2019) demonstrated
       NBSs for hydro-meteorological risk reduction                     that forests can significantly mitigate drought impacts and
                                                                        protect water supplies for crop irrigation.
In this review, NBSs for hydro-meteorological risk reduc-                  The most common NBS measures in urban areas appear
tion have been divided into small- and large-scale solutions            to be intensive green roofs (Burszta-Adamiak and Mrowiec,
(Fig. 3). Small-scale NBSs are usually referred to as NBSs              2013; Carpenter and Kaluvakolanu, 2011; Ercolani et al.,

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L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction                                                          249

Figure 3. Illustration of large and small-scale nature-based solutions (NBSs). Large-scale NBS A illustrates NBSs in mountainous regions
(e.g. afforestation, slope stabilisation, etc.), large-scale NBS B illustrates NBSs along river corridors (e.g. widening river, retention basins,
etc.) and large-scale NBS C illustrates NBSs in coastal regions (e.g. sand dunes, protection dikes and walls, etc.). Typical examples of
small-scale NBSs are green roofs, green walls, rain gardens, permeable pavements, swales, bio-retention, etc.

2018), extensive green roofs (Cipolla et al., 2016; Lee et                 the aim of implementing both concepts and practices of LIDs
al., 2013), rain gardens (Ishimatsu et al., 2017), rainwater               and NBSs as well as various comprehensive urban water
harvesting (Khastagir and Jayasuriya, 2010), dry detention                 management strategies (Chan et al., 2018). Nowadays, the
ponds (Liew et al., 2012), permeable pavements (Shafique et                concept (Sponge City) is widely used when a city increases
al., 2018), bio-retention (Khan et al., 2013; Olszewski and                resilience to climate change. It also combines several sys-
Allen, 2013), vegetated swales (Woznicki et al., 2018) and                 tems, such as the source control system, urban drainage sys-
trees (Mills et al., 2016). However, the authors of these stud-            tem and emergency discharge system.
ies investigated the performance of such measures individu-                   Porous pavement appears to be one of the most popular
ally (i.e. at the specific, local and single site) without evalu-          measures suitable to be combined with other NBSs for urban
ating them in combination with other NBS sites or in hybrid                run-off management. Examples of this are described in Hu
combinations.                                                              et al. (2017), who used inundation modelling to evaluate the
   The literature to date acknowledges that the effectiveness              effectiveness of rainwater harvesting and pervious pavement
of NBSs greatly depends on the magnitude and frequency                     as retrofitting technologies for flood inundation mitigation of
of rainfall events. Green roofs are recognised in reducing                 an urbanised watershed. Damodaram et al. (2010) concluded
peak flows more effectively for smaller-magnitude frequent                 that the combination of rainwater harvesting and permeable
storms than for larger-magnitude infrequent storms (see, for               pavements is likely to be more effective than pond storage for
example, Ercolani et al., 2018). There are also reports that               small storms, while the pond is likely to be more effective to
rain gardens are more effective in dealing with small dis-                 manage run-off from the more intense storms.
charges of rainwater (Ishimatsu et al., 2017). Swales and per-                Several studies argue that multiple-NBS measures can lead
meable pavements are more effective for flood reduction dur-               to a more significant change in run-off regime and more ef-
ing heavier and shorter rainfall events. Zölch et al. (2017)               fective long-term strategies than single-NBS measures (Web-
suggested that the effectiveness of NBSs should be directly                ber et al., 2018). For example, Wu et al. (2018) simulated
linked to their ability to increase (as much as possible) the              eight scenarios changing the percentage of combined green
storage capacities within the area of interest while using open            roof and permeable pavement in an urban setting. The results
spaces that have not been used previously and/or while pro-                show that when green roofs and permeable pavements are ap-
viding benefits to other areas for urban planning.                         plied at all possible locations, a 28 % reduction in maximum
   Several studies evaluated the performance of multiple-                  inundation can be obtained. In comparison, scenarios imple-
NBS (or combined-NBS) measures (i.e. a train of NBSs; see,                 menting either green roofs or permeable pavements alone at
for example, Damodaram et al., 2010; Dong et al., 2017;                    all possible areas experienced a reduction of 14 %. One of
Huang et al., 2014; Luan et al., 2017). One of the most suc-               the main reasons for the superior performance of combined
cessful international projects in combining several NBS mea-               NBSs is that they work in parallel, each treating a different
sures at the urban scale is the Sponge City Programme (SCP)                portion of run-off generated from the sub-catchment (Pap-
in China. The SCP project was commissioned in 2014 with                    palardo et al., 2017). For these combinations, the spatial dis-                                       Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020
L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction

                                                                                     Table 3. Summary of run-off volume and peak flow reduction effectiveness, co-benefits and costs of small-scale NBS measures.
                                                                                      Measures        References         Case           Area or                  Effectiveness            Co-benefits                         Cost per        Remark
                                                                                                                         studies        volume       Run-off              Peak flow                                           square metre∗
                                                                                                                                        covered      volume               reduction
                                                                                                                                        by NBS       reduction
                                                                                      Porous          Shafique et al.    Seoul,         1050 m2      ∼ 30 %–65 %          –               – Removing diffuse                  USD ∼ 252       – More effective
                                                                                      pavement        (2018)             South Korea                                                      pollution                                           in heavier and
                                                                                                      Damodaram et       Texas,         2.99 km2     –                    ∼ 10 %–30 %     – Enhancing recharge to                             shorter rainfall
                                                                                                      al. (2010)         USA                                                              groundwater                                         events
                                                                                      Green roofs     Burszta-           Wroclaw,       2.88 m2      –                    ∼ 54 %–96 %     – Reducing nutrient                 USD ∼ 564       – More efficient
                                                                                                      Adamiak and        Poland                                                           loadings                                            in smaller storm
                                                                                                      Mrowiec (2013)                                                                      – Saving energy                                     events than
                                                                                                      Ercolani et al.    Milan, Italy   0.39 km2     ∼ 15 %–70 %          ∼ 10 %–80 %     – Reducing air pollution                            larger storm
                                                                                                      (2018)                                                                              – Increasing amenity                                events
                                                                                                      Carpenter and      Michigan,      325.2 m2     ∼ 68.25 %            ∼ 88.86 %       value
                                                                                                      Kaluvakolanu       USA
                                                                                      Rain gardens    Ishimatsu et       Japan          1.862 m2     ∼ 36 %–100 %         –               – Providing a scenic                USD ∼ 501       More effective
                                                                                                      al. (2017)                                                                          amenity                                             in dealing with
                                                                                                      Goncalves et       Joinville,     34 139 m2    50 %                 ∼ 48.5 %        – Increasing the median                             small discharges
                                                                                                      al. (2018)         Brazil                                                           property value                                      of rainwater
                                                                                                                                                                                          – Increasing biodiversity

                                                                                                                                                                                                                                                                  Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020
                                                                                      Vegetated       Luan et al.        Beijing,       157 m3       ∼ 0.3 %–3.0 %        ∼ 2.2 %         – Reducing                          USD ∼ 371       – More effective
                                                                                      swales          (2017)             China                                                            concentrations                                      in heavier and
                                                                                                      Huang et al.       Hai He         1500 m3      9.60 %               ∼ 23.56 %       of pollutants                                       shorter rainfall
                                                                                                      (2014)             basin, China                                                     – Increasing biodiversity                           events
                                                                                                                                                                                                                                              – Not suitable in
                                                                                                                                                                                                                                              mountains areas
                                                                                      Rainwater       Khastagir and      Melbourne,     1–5 m3       ∼ 57.8 %–78.7 %      –               – Improving water                   USD ∼ 865
                                                                                      harvesting      Jayasuriya         Australia                                                        quality (TN – total nitrogen) was   per m3
                                                                                                      (2010)                                                                              reduced around
                                                                                                                                                                                          72 %–80 %)
                                                                                                      Damodaram et       Texas,         1.5 km2      –                    ∼ 8 %–10 %
                                                                                                      al. (2010)         USA
                                                                                      Dry             Liew et al.        Selangor,      65 000 m2    –                    ∼ 33 %–46 %     – Providing recreational                            Delaying the
                                                                                      detention       (2012)             Malaysia                                                         benefits                                            time to peak by
                                                                                      pond                                                                                                                                                    40–45 min
Table 3. Continued.

                                                     Measures         References            Case                Area and                     Effectiveness          Co-benefits                                   Cost per        Remark
                                                                                            studies             volume          Run-off               Peak flow                                                   square metre∗
                                                                                                                covered         volume                reduction
                                                                                                                by NBS          reduction
                                                     Detention        Damodaram et          Texas,              73 372 m3       –                     ∼ 20 %        – Providing biodiversity                      USD ∼ 60
                                                     pond             al. (2010)            USA                                                                     benefits
                                                                      Goncalves et          Joinville,          9700 m3         55.7 %                ∼ 43.3 %      – Providing recreational
                                                                      al. (2018)            Brazil                                                                  benefits
                                                     Bio-             Luan et al.           Beijing,            945.93 m3       ∼ 10.2 %–12.1 %       –             – Reducing total suspended solids (TSSs)      USD ∼ 534       – Measure has a
                                                     retention        (2017)                China                                                                   pollution                                                     better reduction
                                                                      Huang et al.          Hai He              1708.6 m3       9.10 %                ∼ 41.65 %     – Reducing TP (total phosphorous) pollution                   effectiveness in
                                                                      (2014)                basin, China                                                                                                                          various rainfall
                                                                      Khan et al.           Calgary             48 m3           ∼ 90 %                –                                                                           intensities
                                                     Infiltration     Huang et al.          Hai He,             3576 m3         30.80%                ∼ 19.44 %     – Reducing water                              USD ∼ 74
                                                     trench           (2014)                China                                                                   pollutant
                                                                      Goncalves et          Joinville,          34 139 m2       55.9 %                ∼ 53.4 %      – Improving surface
                                                                      al. (2018)            Brazil                                                                  water quality
                                                     Green roof       Damodaram et          Texas,              4.49 km2        –                     ∼ 10 %–35 %   – Saving energy                                               – More effective in
                                                     and porous       al. (2010)            USA                                                                     – Increasing amenity                                          smaller events
                                                     pavement                                                                                                       value
                                                     Swale and        Behroozi et al.       Tehran,             –               5 %–32 %              ∼ 10 %–21 %   – Decreasing TSSs                                             – More effective in
                                                     porous           (2018)                Iran                                                                    pollution 50 %–60 %                                           smaller events
                                                     Rainwater        Damodaram et          Texas,              4.49 km2        –                     ∼ 20 %–40 %   – Removing diffuse                                            – More effective in
                                                                                                                                                                                                                                                        L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction

                                                     harvesting       al. (2010)            USA                                                                     pollution                                                     smaller events
                                                     and porous
                                                     Detention        Goncalves et          Joinville,          18 327 m2       70.8 %                ∼ 60.0 %      – Providing a scenic
                                                     pond and         al. (2018)            Brazil                                                                  amenity
                                                     rain garden
                                                     Detention        Goncalves et          Joinville,          18 327 m2       75.1 %                ∼ 67.8 %      – Improving surface
                                                     pond and         al. (2018)            Brazil                                                                  water quality
                                                   ∗ Cost of each measure is based on CNT (2009), Nordman et al. (2018) and De Risi et al. (2018).

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252                                   L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction

tribution should be carefully considered because it can im-       effectiveness, co-benefits and cost of large-scale NBS mea-
prove the run-off regime better when compared to centralised      sures is shown in Table 4.
NBSs (Loperfido et al., 2014).                                       Only few articles have addressed the combined behaviour
   Further research on the use of combined NBSs and grey in-      of NBSs at large scales. One of the possible reasons is that
frastructure (i.e. hybrid measures) is desirable, as only three   large-scale systems are more complex than small-scale sys-
contributions were found in the review. Alves et al. (2016)       tems. The most common large-scale NBSs are flood storage
presented a novel method to select, evaluate and place differ-    basins (De Risi et al., 2018) and preservation and regener-
ent hybrid measures for retrofitting urban drainage systems.      ation of forests in flood-prone areas (Bhattacharjee and Be-
However, only fundamental aspects were touched upon in            hera, 2018), making more room for the river (Klijn et al.,
the methodology, and they suggested that future work should       2013), river restoration (Chou, 2016), wetlands (Thorslund
include the possibility of considering stakeholders’ prefer-      et al., 2017) and mountain forestation (Casteller et al., 2018).
ences or flexibility within the method. In the work of Vo-           A classic example of a large-scale NBS implementation
jinovic et al. (2017), a methodological framework that com-       is the Room for the River Programme implemented along
bines ecosystem services (flood protection, education, art and    the Rhine and Meuse rivers in the Netherlands. The Room
culture, recreation, and tourism) with economic analysis for      for the River Programme consisted of 39 local projects
the selection of multi-functional measures and consideration      based on nine different types of measures (Klijn et al.,
of small- and large-scale NBSs has been discussed for the         2013). These measures are floodplain lowering, dike reloca-
case of Ayutthaya in Thailand. Onuma and Tsuge (2018)             tion, groyne lowering, summer bed deepening, water stor-
compared the cost and benefits and performance of NBSs            age, bypassed and floodways, high-water channels, obstacle
and grey infrastructures, concluding that NBSs are likely to      removal, and dike strengthening. The benefits that the pro-
be more effective when implemented through cooperation            gramme achieved are more than just reducing flooding, also
with local people, whereas hybrid solutions are more effec-       increasing opportunities for recreation, habitat and biodiver-
tive than a single NBS in terms of performance.                   sity in the area (Klijn et al., 2013). Another case study of
   The first limitation of the above studies is that they only    a large-scale NBS is the Laojie River project in Taoyuan in
assess the effectiveness of NBSs at urban scales. This may        Taiwan. The study focused on changing the channelised, cul-
not be sufficient for large events, as climate change is likely   verted, flood-control watercourse into an accessible green in-
to increase the frequency and intensity of future events (Qin     frastructure corridor for the public (Chou, 2016). The land-
et al., 2013). A large-scale NBS could be a solution for storm    scape changes resulting from this project have increased
events with large magnitude and long duration, which is usu-      recreation activities and improved the aesthetic value in the
ally the case for disaster risk reduction applications, and       area.
therefore research in this direction is highly desirable (Gi-        NBSs may benefit people in coastal areas by reducing risk
acomoni et al., 2012). Although Fu et al. (2018) analysed         from storm surges, wave energy, coastal flooding and ero-
variations in run-off for different scales and land-uses, the     sion, as documented by several authors (see, for example,
impact of NBSs was only examined for the small urban scale.       Van Coppenolle, 2018; Joyce et al., 2017; Ruckelshaus et al.,
Another limitation is that none of these contributions incor-     2016; Sutton-Grier et al., 2018). NBSs for coastal areas can
porated cost–benefit analyses (CBAs). CBAs can be used as a       be implemented either at large or small scales. They include
tool to support the decision-making process, as they serve the    dunes, beaches, oyster and coral reefs, mangroves, seagrass
feasibility of implementation costs and the potential benefits    beds, and marshes. These measures can also provide habi-
of NBSs.                                                          tats for different species such as fish, birds and other wildlife
                                                                  (Ruckelshaus et al., 2016). Schoonees et al. (2019) provided
                                                                  lists of general recommendations, technical guidelines and
4.1.2   Research on large-scale NBSs for
                                                                  policies, and design considerations for NBSs in coastal areas.
        hydro-meteorological risk reduction
                                                                  However, only a few articles of the 146 reviewed focused on
                                                                  the potential benefits of NBSs in coastal areas.
Large-scale water balance, water fluxes, water management            Casteller et al. (2018) concluded that native mountain
and ecosystem services are affected by future changes such        forests could be used to reduce hydro-meteorological risk
as climate change, land use changes, water use changes and        such as flash floods and landslides. Moreover, the use of
population growth. To address such challenges, large-scale        NBSs in different forest ecosystems to reduce shallow land-
NBSs are needed to make more space for water to retain, de-       slide impacts should be addressed (de Jesús Arce-Mojica
celerate, infiltrate, bypass and discharge (Cheng et al., 2017;   et al., 2019). To reduce the impact of large-scale hydro-
Thorslund et al., 2017). Generally, a large-scale NBS com-        meteorological events, more research is needed on large-
bines different NBSs within a larger system to achieve better     scale NBSs and their hybrid combinations designed to at-
long-term strategies. There are some examples of NBS mea-         tenuate flows and improve drainage. They should be imple-
sures for hydro-meteorological risk reduction summarised in       mented to include improvements in solid waste management,
McVittie et al. (2018) and Sahani et al. (2019). A summary of

Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020                 
L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction                                                                           253

Table 4. Summary of effectiveness, co-benefits and costs of large-scale NBS measures.

  Measures         References         Case studies             Area or volume   Effectiveness           Co-benefits                        Cost
                                                               by NBSs
  De-culverting    Chou (2016)        Laojie River,            3 km             – It can reduce flood   – Increasing landscape value       EUR ∼ 16.92 million
  (river                              Taiwan                                    risk up to 100-year     – Increasing recreational value
  restoration)                                                                  return period
  Floodplain       Klijn et al.       Deventer                 5.01 km2         – It can reduce water   – Increasing nature area           EUR ∼ 136.7 million
  lowering         (2013)             Netherlands                               level 19 cm             – Increasing agriculture value
  Dike             Klijn et al.       Nijmegen-                2.42 km2         – It can reduce water   – Increasing floodplain area       EUR ∼ 342.60 million
  relocation and   (2013)             Lent,                                     level 34 cm             – Increasing recreational value
  floodplain                          Netherlands
  Floodwater       Klijn et al.       Volkenrak-               200 × 106 m3     – It can reduce water   – Increasing habitat and           EUR ∼ 386.20 million
  storage          (2013)             Zoommeer, Netherlands                     level 50 cm             biodiversity in the area
                                                                                                        – Increasing recreational value
  Green            Klijn et al.       Veessen-                 14.10 km2        – It can reduce water   – Increasing floodplain area
  floodway         (2013)             Wapenveld, Netherlands                    level 71 cm             – Increasing recreational value
  Wetlands         Van Coppenolle                                               – It can mitigate       – Providing shoreline protection
  (mangroves       (2018), Gedan et                                             storm surge 80 %        services
  and salt         al. (2011)                                                   – It can protect
  marshes)                                                                      against tsunami

                                                                                  4.2.1      Selection of NBSs

                                                                                  It has been a well-accepted fact that not all NBSs are suit-
                                                                                  able for all conditions. Therefore, it is important to consider
                                                                                  the feasibility and constraints at the site at an early stage
                                                                                  in the selection process. The first consideration in select-
Figure 4. Evaluation process of nature-based solutions. The process               ing NBSs is to define the objective such as the target area
includes selecting possible measures and evaluating and optimising
                                                                                  (i.e. urban or rural) and performance requirements such as
measures’ performance using available tools.
                                                                                  quantity and/or quality (Romnée and De Herde, 2015; Zhang
                                                                                  and Chui, 2018). For example, Pappalardo et al. (2017) chose
community-based river cleaning programmes and reforesta-                          permeable pavements and green roofs because they can de-
tion (De Risi et al., 2018).                                                      tain run-off or enhance infiltration to the subsoil. Another
                                                                                  approach is to consider both primary benefits and key co-
4.2    Techniques, methods and tools for planning,                                benefits. For instance, Majidi et al. (2019) developed a frame-
       selecting, evaluating and implementing NBSs                                work to select NBSs to reduce flood risk and enhance human
                                                                                  thermal comfort (reducing heat stress). Many authors suggest
Figure 4 illustrates a typical process for the selection and                      restricting the choice of appropriate NBSs based on com-
evaluation of NBSs. The process starts by selecting possi-                        mon site constraints such as land use, soil type, groundwater
ble measures that correspond to the local characteristics and                     depth, catchment characteristics, political and financial reg-
project’s target. The next step is concerned with evaluating                      ulations, amenities, environmental requirements, and space
the measures’ performance using numerical models, cost–                           available (Eaton, 2018; Joyce et al., 2017; Nordman et al.,
benefit analysis and/or multi-criteria analysis. For more com-                    2018; Oraei Zare et al., 2012). For example, Eaton (2018)
plex systems with a large number of scenarios and parame-                         selected bio-retention measures because they are more suit-
ters, optimisation can be used to maximise the benefits and                       able in low-density residential land use. Moreover, the study
minimise the costs. The techniques, methods and tools for                         of Reynaud et al. (2017) describes how the type of NBS
planning, selecting, evaluating and implementing NBSs are                         has an impact on individuals’ preference for ecosystem ser-
reviewed in the following section.                                                vices. Therefore, a screening analysis is necessary for select-
                                                                                  ing the NBS measures that are best suited to local constraints
                                                                                  and objectives, providing decision makers with valuable in-
                                                                                  formation. The way forward in the selection of NBSs is to
                                                                                  consider spatial planning principles to locate the position for                                                 Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020
254                                     L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction

measures. Spatial planning principles can facilitate and stim-       in large catchments. Yang et al. (2018) proposed relative per-
ulate discussion among local communities, researchers, pol-          formance evaluation (RPE) methods, which use a score to
icymakers and government authorities.                                calculate the performance for all alternatives. This score is
                                                                     calculated as the weighted sum of the scores of individual
4.2.2   Frameworks and methods for evaluation of NBSs                indicators.
                                                                        From the discussion above, it can be observed that there
There are several frameworks and methods that can be used            are still challenges in evaluating intangible benefits of NBSs
to evaluate the performance indicators of NBSs discussed in          and incorporating stakeholders’ preferences into the process.
this review. One of the most popular evaluation approaches           For complex systems with a large number of scenarios and
is to analyse, simulate and model hydrology, hydraulics and          parameters, simple trial-and-error methods may not be the
water balance processes. This information is then used to            feasible approach. In such cases, an automated optimisation
support decision makers, planners and stakeholders in their          method could be effectively applied to handle these tasks and
evaluation of performance and potential of NBSs by compar-           to combine the above-mentioned methods. There is also a
ing modelled results against the current situation, baseline         challenge in combining a range of aspects that can and cannot
scenario or targets (Jia et al., 2015).                              be expressed in monetary terms into the same framework of
   In addition to hydrological and hydraulic analyses, cost–         analysis.
benefit analyses are often used to select and evaluate NBSs
(Huang et al., 2018; Nordman et al., 2018; Watson et al.,            4.2.3   Optimal configuration of NBSs
2016; Webber et al., 2018). The common benefits consid-
ered include prevented damage costs, omitted infrastruc-             In order to implement NBSs, typical selection factors include
tures and prevented agricultural losses. One cost–benefit ap-        the number of NBS measures, size, location and potential
proach is to evaluate NBSs by applying the whole life cycle          combinations of NBSs. Optimisation of NBS strategies has
costing (LCC) approach, including construction, operation,           been increasingly used in the context of urban stormwater
maintenance and opportunity costs (Nordman et al., 2018),            management. Most of the studies focus on minimising water
and return on investment (ROI; De Risi et al., 2018).                quantity and improving water quality by selecting the type,
   Another method for the evaluation of NBSs is multi-               design, size and location of NBSs (Behroozi et al., 2018; Gao
criteria analysis (MCA), which has the potential to integrate        et al., 2015; Giacomoni and Joseph, 2017; Zhang and Chui,
and overcome the differences between social and technical            2018). Zhang and Chui (2018) systematically reviewed opti-
approaches (Loc et al., 2017). It can be used to structure com-      misation models that have different structures, objectives and
plex issues and help find a better understanding of costs and        allocation components. This section reviews some examples
benefits. Such analysis is useful for decision makers when           of using optimisation to assess NBSs.
there are multiple and conflicting criteria to be considered            A comprehensive modelling system typically refers to
(Alves et al., 2018b; Loos and Rogers, 2016). The MCA                an optimisation package tool that integrates an “easy-
takes different criteria into account and assigns weights to         to-use” user interface with physically based determinis-
each criterion. This process can produce a ranking of the dif-       tic models. Examples include SUSTAIN (the System for
ferent measures that can be implemented on the site (Chow            Urban Stormwater Treatment and Analysis IntegratioN;
et al., 2014; Jia et al., 2015). For example, Loc et al. (2017)      Zhang and Chui, 2018) and best management practice de-
integrated the results from numerical modelling and social           cision support (BMPDSS; Gao et al., 2015). The SUSTAIN
surveys into a MCA and ranked the alternatives based on the          model was developed by the US Environmental Protection
evaluation criteria of flood mitigation, pollutant removal and       Agency (US EPA) and aims to provide decision makers with
aesthetics. Loos and Rogers (2016) applied multi-attribute           support in the process of selection and placement of NBS
utility theory (MAUT) to assess utility values for each al-          measures and to optimise the hydrological performance and
ternative by assuming that preference and utility are indepen-       cost-effectiveness of NBSs in the urban watershed (Leslie et
dent of each other. Petit-Boix et al. (2017) recommended that        al., 2009; C. Li et al., 2018). There are several studies that ap-
future research combine the economic value of the predicted          ply SUSTAIN with the aim of minimising the cost of NBSs
material and ecological damage, risk assessment models and           for both run-off quantity (flow volume and peak flow) and
environmental impacts of NBSs.                                       run-off quality (pollutant removal; Gao et al., 2015; N. Li et
   Since not all assessments can be done with modelling              al., 2018). It is, however, important to note that comprehen-
alone, interviews and fieldwork are often necessary. For in-         sive modelling systems are not always easily modified to fit
stance, Chou (2016) used 18 open questions from six top-             with the specific needs of users.
ics, namely accessibility, activities, public facilities, environ-      Another optimisation tool approach is integrated model–
mental quality, ecological value and flood prevention. These         algorithm tools, which combine numerical (hydrological–
questions are used to evaluate the qualitative performance of        hydrodynamic) models with optimisation algorithms. A pop-
river restoration. However, some of the methods are only ap-         ular optimisation method used to evaluate NBS perfor-
propriate for small-scale applications and cannot be applied         mance is a multialgorithm, genetically adaptive multiobjec-

Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020                    
L. Ruangpan et al.: Nature-based solutions for hydro-meteorological risk reduction                                              255

tive (AMALGAM) method using the multilevel spatial opti-             two-dimensional models in the optimisation analysis. This is
misation (MLSOP) framework (Liu et al., 2016).                       particularly important when considering estimation of flood
   In the reviewed articles, the non-dominated sorting ge-           damages and other flood propagation-related impacts.
netic algorithm II (NSGA-II) is used in most of the stud-
ies to date. Wang et al. (2015) concluded that NSGA-II is            4.2.4   Tools for selection, evaluation and operation
one of the most popular multiobjective evolutionary algo-                    of NBSs
rithms (MOEAs) despite limited parameter tuning features
and generally outperformed the other MOEAs in relation               Recently, several selection and evaluation tools have been
to the set of solutions generated. There are several exam-           developed in order to assist stakeholders in screening, se-
ples of the use of NSGA-II. Oraei Zare et al. (2012) min-            lecting and visualising NBS measures. Examples of web-
imised run-off quantity while maximising the improvement             based applications developed to screen urban NBS measures
of water quality and maximising reliability. Karamouz and            are the green–blue design tool (atelier GROENBLAUW,
Nazif (2013) minimised the cost of flood damage while min-           2019), PEARL KB (PEARL, 2019), climate adaptation app
imising NBS cost in order to improve system performance              (Bosch Slabbers et al., 2019) and Naturally Resilient Com-
in dealing with the emerging future conditions under cli-            munities solutions (Naturally Resilient Communities, 2019).
mate change. Yazdi and Salehi Neyshabouri (2014) opti-               These web-based tools allow the user to filter NBSs in rela-
mised cost-effectiveness, which focused on land use change           tion to their problem type, measure, land use, scale and loca-
strategies including orchard, brush and seeding measures in          tion.
different parts of the watershed. All of the above-mentioned            In addition to the above, there are also tools that combine
studies coupled NSGA-II with the Storm Water Management              both the selection and evaluation processes together to use
Model (SWMM) developed by US EPA (Cipolla et al., 2016;              as planning support systems tool. An example is the SuD se-
J. Li et al., 2018; Mei et al., 2018; Tao et al., 2017; Wu et al.,   lection and location (SUDSLOC) tool, which is a GIS tool
2018; Yang et al., 2018; Zhu and Chen, 2017) to address the          linked to an integrated 1-D hydraulic sewer model and a 2-D
optimisation problems.                                               surface model. UrbanBEATS (the Urban Biophysical Envi-
   There are two different optimisation methods of parti-            ronments and Technologies Simulator) aims to support the
cle swarm optimisation (PSO) which have been found in                planning and implementation of WSUD infrastructure in ur-
the course of this review. The modified particle swarm op-           ban environments (Kuller et al., 2018). Other tools that can
timisation (MPSO) is used by Duan et al. (2016) to solve             be used to select and evaluate potential NBS interventions are
the multi-objective optimal (MOO) of the cost-effectiveness          Long-Term Hydrologic Impact Assessment-Low Impact De-
of NBS-based detention tank design. Similarly, Behroozi et           velopment (L-THIA-LID; Ahiablame et al., 2012; Liu et al.,
al. (2018) used the multi-objective particle swarm optimisa-         2015) and the GIS-based tool called the Adaptation Support
tion (MOPSO) by coupling it with SWMM to optimise the                Tool (AST; Voskamp and Van de Ven, 2015). Although these
peak flow and mean total suspended solid (TSS) concentra-            tools could be useful in assisting decision makers, some of
tion reduction by changing the combinations of NBSs.                 them may not be suitable for every location and scale. For
   Another algorithm that is used for optimising the perfor-         example, source data required into L-THIA-LID cover only
mance of NBSs is simulated annealing (SA). SA is a gen-              the US, and QUADEAU (Romnée and De Herde, 2015) is
eral probability optimisation algorithm that applies thermo-         only suitable for urban stormwater management on a public-
dynamic theories in statistics. An example of a study with SA        space scale.
is given by Huang et al. (2018), who automatically linked               In addition to the above, other models such as MIKE pack-
SA with SWMM to maximise the cost and benefit for flood              ages developed by DHI (Semadeni-Davies et al., 2008), the
mitigation and layout design. The cost–benefit analysis is           soil and water assessment tool (SWAT; Cheng et al., 2017),
computed using annual cost, which includes both annual               IHMORS (Herrera et al., 2017), and the urban water option-
fixed cost and annual maintenance cost. Another study that           eering tool (UWOT; Rozos et al., 2013) can be effectively
applied SA is Chen et al. (2017), who combined SA with               used in the analysis effectiveness of NBSs.
SWMM to locate NBSs in Hsinchu County in northern Tai-                  To date, very few tools have been developed to calculate
wan by considering three objective functions. These were             multiple benefits of NBSs in monetary terms as well as to ad-
minimising depths, durations and the number of inundation            dress their qualitative benefits. Some examples are the Ben-
points in the watershed.                                             efits of SuDs Tool (BeST), which provides a structured ap-
   It can be observed that most of the optimisation models to        proach to evaluating potential benefits of NBSs (Digman et
date (both the comprehensive modelling system and model              al., 2017; Donnell et al., 2018; Fenner, 2017), and the MU-
algorithms) are coupled with SWMM for urban storm man-               SIC (Model for Urban Stormwater Improvement Conceptu-
agement. There is still a lack of research that uses optimi-         alization) tool, which is a conceptual planning and design
sation to maximise the efficiency of NBSs on a large scale           tool that also contains a life cycle costing module for differ-
as well as combining other co-benefits in optimisation (Ta-          ent NBSs that are implemented in Australia (Khastagir and
ble 3). Furthermore, there is a lack of research that employs        Jayasuriya, 2010; Schubert et al., 2017).                               Nat. Hazards Earth Syst. Sci., 20, 243–270, 2020
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