A Policy Diagnosis of Urban Rainwater Management in the Mediterranean: Comparative Planning Frameworks in Turkey and Spain

Climate change has become a defining condition for urban systems, reshaping water cycles and exposing the limitations of conventional infrastructure and planning paradigms [1]. Rising temperatures, altered precipitation patterns, and increasingly frequent extremes place particular pressure on Mediterranean cities, which are recognized as climate-change hotspots due to their sensitivity to hydrological variability [2, 3].

Climate projections consistently indicate declining annual precipitation combined with increased rainfall intensity and irregularity. As a result, Mediterranean cities face dual and interconnected pressures: managing excess water during extreme rainfall events while simultaneously coping with prolonged drought and growing water scarcity [1, 4]. These conditions directly challenge the foundational assumptions of conventional rainwater management systems, which have historically been shaped by an engineering paradigm prioritizing rapid conveyance and removal [5]. While effective under relatively stable climatic conditions, such systems have proven increasingly inadequate in contexts characterized by greater uncertainty and variability [6].

In response to these limitations, alternative approaches such as Sustainable Urban Drainage Systems (SUDS) and nature-based solutions (NBS) have gained prominence in both research and practice. These approaches seek to retain, infiltrate, store, and reuse rainwater at or near its source, reducing runoff volumes while enhancing urban resilience [7]. However, an expanding body of literature emphasizes that the success of such approaches depends not only on their technical performance but also on their institutional embedding within planning systems, regulatory frameworks, and governance arrangements. Rainwater management is increasingly conceptualized as a socio-technical challenge shaped by planning cultures, scalar relationships, and decision-making processes [8-10]. Despite the growing recognition of the socio-technical nature of urban rainwater management, most studies evaluate these approaches primarily through their technical or hydrological performance. Comparatively less attention has been paid to how planning systems and institutional structures condition whether such measures can be implemented, coordinated across scales, and sustained over time. Consequently, the relationship between planning system structure and urban rainwater resilience remains insufficiently examined.

This study approaches rainwater management as a planning and governance problem rather than a purely technical one. It examines whether urban adaptive capacity emerges from the presence of specific technical measures or from the coherence of planning systems that organize them. To investigate this question, the research adopts a multi-scalar analytical framework tracing how rainwater policies are translated from basin-scale strategies to urban planning and infrastructure implementation. Turkey and Spain are selected not as exemplary or opposing cases, but as analytically comparable planning contexts operating under similar Mediterranean climatic pressures while differing in institutional organization and planning coordination. By analyzing national legislation, climate adaptation strategies, river basin management plans (Marmara and Tagus), and local planning documents in Istanbul and Madrid, the study evaluates how planning hierarchies structure the framing of rainwater as risk or resource, the bindingness of measures, and the existence of measurable targets.

The article tests the proposition that differences in urban rainwater resilience cannot be explained solely by technological capacity or climate exposure, but are associated with institutional characteristics of planning systems, particularly their degree of bindingness, cross-scale integration, and the translation of basin-level strategies into local spatial planning decisions. Accordingly, the paper conceptualizes urban resilience as a planning outcome and examines how planning frameworks shape the integration of rainwater into urban adaptation policies.

Spatial differentiation of risk is becoming increasingly evident. Lazoglou et al. [12] identify the southeastern Mediterranean as a high-risk sub-region. Under the RCP8.5 scenario, total rainfall is expected to decrease by 30% to 40% in parts of the southern Mediterranean by the end of the century [4]. Importantly, increased rainfall intensity is not expected to compensate for overall declines, leading to the simultaneous occurrence of flooding and water scarcity. Urbanization trends further intensify these pressures. Rapid population growth and expanding urban areas – particularly along the eastern and southern coasts – increase water demand and amplify flood risks [13]. Rising temperatures accelerate evaporation and reduce the efficiency of large-scale storage systems such as dams, undermining the reliability of centralized water supplies [14].

In response to growing pressure on urban infrastructure, alternative approaches emphasizing the retention, infiltration, storage, and reuse of rainwater have gained prominence. NBS, adopted by the European Commission in 2008, are defined as nature-inspired and nature-supported systems that are cost-effective, enhance resilience, and provide environmental, social, and economic benefits through locally adapted and resource-efficient interventions [7]. In Mediterranean European countries such as Spain and Italy, these approaches are increasingly operationalized through SUDS, which aim to align the urban water cycle with natural hydrological processes through flexible, site-specific designs at multiple scales.

SUDS are compatible with key European policy frameworks, including the European Green Deal, the 2030 EU Biodiversity Strategy, the Water Framework Directive, and the Floods Directive. Empirical studies demonstrate that SUDS provide an effective framework for implementing NBS in urban rainwater management and for strengthening the resilience of the urban water cycle [15, 16]. Southern European countries within the Mediterranean climate zone, particularly Spain and Italy, have made notable progress in SUDS implementation [17, 18]. However, the effectiveness of such approaches ultimately depends on how rainwater is conceptualized within planning systems, regulatory frameworks, and planning structures, rather than on their technical performance alone.

5.1 National legislation

Among the Mediterranean countries, Spain's studies and publications on SUDS are particularly noteworthy [23]. Since 1998, SUDS have been implemented incrementally in new Spanish urban projects, often independently of regional legal frameworks. From 2005, various regional regulations and guidelines tailored to specific climatic conditions emerged [24]. Following the formal inclusion of SUDS in national regulations and strategies in 2016, multi-criteria decision-making tools were developed at the urban scale. A national framework now enables regional and local authorities to establish their own mandatory, incentive or advisory instruments, supported by systematic evaluation methods [16, 25]. The most recent advancement, Real Decreto 665/2023, amends Hydraulic Public Domain regulations to strongly incentivize SUDS. This reform mandates that local governments develop rainwater management strategies and integrate SUDS into monitoring and reporting procedures, building on the 2016 prioritization of SUDS in new urban developments.

The 2023 regulation establishes binding, nationwide standards, requiring integrated SUDS plans (PIGSS—Plan Integral de Gestión del Sistema de Saneamiento) for settlements with populations exceeding 50,000. These plans must be guided by capacity management principles, precipitation scenarios, and multifaceted risk assessments related to drought and flooding. Furthermore, the regulation mandates digital monitoring and recording systems to support evidence-based decision-making in water-cycle management (Appendix A, Doc 1). By positioning SUDS at the core of national water management, rather than treating it as an isolated tool within housing or urban planning, this initiative promotes a comprehensive, whole-water-cycle approach. This approach effectively integrates drainage, groundwater protection, water resources, and pollution control, emphasizing the interrelationships within the urban water cycle.

Table 4. Comparative assessment of policy documents at the national legislation

Table 5. Comparative assessment of policy documents at the national climate change action plans

Two regulations in Turkey explicitly address SUDS: the 2017 Rainwater Collection, Storage and Discharge Systems Regulation and the amendments on rainwater storage in the Planned Areas Zoning Regulation (2021, with an additional amendment in 2025). As summarized in Table 4, this framework diverges from the Real Decreto paradigm by treating rainwater primarily as an infrastructure input rather than as a flow requiring integrated management. The 2017 regulation focuses on technical design and implementation, emphasizing engineering components such as pipe systems, storage structures, filtration units, and discharge points (see Section 4) It neither mandates rainwater systems nor directly link them to planning instruments, instead defining technical conditions applicable when such systems are installed. While it contributes to establishing a common terminology for rainwater management in Turkey, the regulation addresses the rainwater cycle and basin-scale management in a fragmented manner (Appendix A, Doc 2).

The 2021 Planned Areas Zoning Regulation amendment introduces limitations related to scale selection and integration with planning. Under Article 5, it mandates roof-surface rainwater storage for parcels larger than 2,000 m², while implementation for smaller parcels is left to the discretion of local authorities (Appendix A, Doc 3). This approach reduces rainwater management to building-scale technical measures rather than adopting a holistic hydrological perspective. The 2,000 m² threshold is not linked to rainfall patterns or basin characteristics, effectively excluding smaller parcels and most urban open spaces, thereby weakening network coherence. The 2025 amendment, within Article 6, strengthens provisions on rainwater use in terms of scope and technical detail but continues to operate primarily at the parcel scale. Numerical thresholds for roof area and storage volume are introduced, and compliance with technical standards becomes an integral part of the permitting process (Appendix A, Doc 4).

As presented in the evaluation results in Table 5, while the national legislation in Turkey treats rainwater as a 'technical detail to be managed at the parcel scale,' the Spanish framework conceptualizes it as a 'strategic resource and an integral component of spatial planning.' The high performance of the Spanish legislation across all three criteria is explicitly grounded in Article 259 of Real Decreto 665/2023, which mandates the integration of drainage strategies into broader urban systems while enforcing binding standards for water circularity. In contrast, the score of 0 received by Turkey in the Integration criterion—despite the parcel-based requirements in the Planned Areas Zoning Regulation—serves as the most concrete evidence of the systemic disconnect between national infrastructure regulations and urban planning processes.

The evaluation of national-scale action plans reveals that while Turkey exhibits a higher institutional commitment at the strategic level than Spain, there are fundamental conceptual differences in how the water cycle is addressed. Turkey’s Climate Change Adaptation Strategy and Action Plan (2024-2030) outperforms its Spanish counterpart in the bindingness criterion with a score of 2. This score is justified by the administrative obligations and implementation responsibilities defined under "Strategy Implementation, Article 9" (page 117). The document’s Circularity performance (2 points) is verified by the integrated perspective on water recovery and rainwater harvesting developed under "Strategic Goal 3" (page 77) (Appendix A, Doc 5).

The second critical Turkish document at this scale, the Water Efficiency Strategy Document and Action Plan (2023-2033), receives 1 point for Bindingness due to the administrative framework provided under "Goal 1" on page 73. For Circularity, it scores 1 point as it addresses the technical potential for water reuse (page 22). However, the "0" score for Spatial Integration in both Turkish documents confirms that these strategic goals lack concrete spatial standards or design criteria required to provide direct input for sub-scale planning processes (Appendix A, Doc 6).

On the Spanish side, PNACC (2021-2030) scores 1 point for bindingness, as it remains largely advisory. However, it reaches the maximum threshold with a score of 3 in the Circularity criterion. This high performance is justified in "Section 7.3: Water Resources," where the document defines water resources as a relational cycle between drought and flood risks and adopts a holistic approach to water conservation. Similar to the Turkish examples, this Spanish strategic document scores "0" in the Integration criterion as it does not function as a direct spatial implementation tool (Appendix A, Doc 7).

While the action plans of both countries acknowledge the importance of rainwater use and SUDS, their underlying planning logics differ markedly. Turkey’s plans prioritize technically specified actions and discrete interventions, focusing on what should be implemented. Spain’s PNACC, in contrast, emphasizes organizational coherence, and the integration of adaptation objectives across planning scales, focusing on how adaptation should be structured within the planning system. Despite growing institutional awareness in Turkey, rainwater-related measures remain fragmented, insufficiently linked to basin-scale objectives, and highly dependent on local implementation capacity. In Spain, rainwater management is embedded within the broader urbanization-basin-climate nexus, functioning as a core instrument on climate change adaptation rather than a supplementary technical measure.

5.2 National level guides

Turkey currently lacks a national-level guideline on urban drainage systems, representing a significant systemic divergence from the Spanish model. Spain has established a comprehensive framework titled Guías de Adaptación al Riesgo de Inundación: Sistemas Urbanos de Drenaje Sostenible, which serves as a critical technical bridge missing in the Turkish planning hierarchy. Although not strictly binding, this guide scores 2 for Bindingness and 2 for Spatial Integration by providing adaptable technical solutions and infrastructure typologies tailored to Spain’s diverse climatic conditions (Appendix A, Doc 8).

In the Spanish context, the guide mandates that SUDS typologies be scaled across three distinct zones: infiltration and deceleration for the wet-temperate north; storage-oriented micro-rain gardens for the Mediterranean region; and bio-filters with drought-tolerant vegetation for semi-arid areas. By establishing these specific technical standards and runoff coefficients, the guide achieves a maximum score of 3 for Circularity. It transforms rainwater from a waste product into a site-specific resource, ensuring that strategic circularity goals are translated into mandatory, place-specific design requirements.

Consequently, while Spain’s guide formally embeds sustainable drainage within national climate policy through a uniform nationwide terminology, the Turkish framework remains fragmented. In Turkey, although separate action plans address climate change and water efficiency, the absence of a national design manual results in a '0' score across all criteria at this scale. Without standardized parameters for SUDS design, site selection, and volume calculation, sustainable drainage in Turkey tends to remain at a conceptual level, forcing local authorities to rely on traditional gray-infrastructure solutions instead of operationalizing resilient, spatial interventions.

5.3 Regional level basin management plans

In this section, at the regional level, plans for the Marmara Basin and the Tagus River Basin encompassing Istanbul and Madrid respectively are examined. The evaluation at this scale is based on a total of six documents, covering the general management plan, flood risk management plan, and drought management plan for each basin (Table 6).

Table 6. Comparative assessment of policy documents at the regional level basin management plans

The Tagus basin plans are founded on safeguarding and regulating the basin’s natural dynamics by maintaining ecosystem and hydro morphological integrity within the water cycle. SUDS term is not typically used as a heading or explicit category, since basin management plans are framed around the broader hydrological cycle rather than urban infrastructure terminology. Instead, they embed core SUDS principles, including the protection of natural flow regimes, the joint management of floods and droughts, and the reduction of urbanization pressures on the water system (Appendix A, Doc 9, 10, 11). Spain’s basin plans follow a standardized structure common to other EU river basins: their methodology, mandatory contents, and section order are defined by the Floods Directive and the Water Framework Directive, and each plan is revised on a six-year cycle [26].

In Marmara, flood and drought are handled through separate two plans, the Marmara Flood Management Plan and the Marmara Drought Management Plan, whereas in the Tagus Basin they are administratively distinct but managed within a holistic framework with shared performance targets that complement the urban water cycle. The Marmara Flood Management Plan prioritizes stream improvement (e.g., bed cleaning and channel arrangement) without explicit links to urban infrastructure (Appendix A, Doc 12). The Drought Management Plan mentions green infrastructure for rainwater management only in recommendations and does not integrate these measures into scenarios, water budgets, supply–demand projections, or drought severity models (Appendix A, Doc 13, 14, 15).

The evaluation of the Regional Basin Management Plans reveals a fragmented structure within the Turkish planning hierarchy, where strategic goals at the basin scale struggle to find a binding pathway to local implementation. In the Marmara Basin Management Plan, the bindingness criterion receives a score of 2, supported by the mandatory "Program of Measures" defined in Section 7. This section outlines the administrative responsibilities and requirements for basin-level water protection. Regarding spatial integration, the plan scores 1 based on the environmental objectives detailed in Section 5, which provide a conceptual framework but lack the specific spatial indicators needed for direct sub-scale planning input. However, the plan demonstrates a stronger performance in circularity (Score: 2); within Section 2, the baseline characteristics of the basin are defined by acknowledging both flood and drought risks relationally, explicitly identifying rainwater as a potential resource for the region.

Conversely, the thematic management plans—the Marmara Basin Flood Management Plan and the Drought Management Plan—exhibit a more disconnected and advisory nature. Both documents receive a low score of 1 for bindingness, as their provisions for urban rainwater systems remain largely conceptual. In the Flood Management Plan (Section 7) and the Drought Management Plan (Sections 5 and 6), rainwater interventions are mentioned as strategic necessities but lack the legal force required to mandate specific local-level implementations. This fragmentation is most evident in the Integration scores; while the Flood Management Plan scores 2 due to its specific risk mapping, the Drought Management Plan scores 0, confirming that it fails to provide any concrete spatial standards or technical inputs for urban planning at the lower scales.

The maximum score of 3 for Bindingness in the Tagus Basin Management Plan is justified by the mandatory monitoring and legal enforcement mechanisms detailed in Section 16: El Programa de Medidas. Furthermore, the plan achieves a score of 3 for Integration as Section 17: La Normativa explicitly defines the necessary spatial inputs and standards for sub-scale planning frameworks. Regarding Circularity, the plan is evaluated with a score of 3 because Section 16 conceptualizes extreme weather events—both drought and flood—as part of a relational cycle, thereby establishing a holistic management mechanism for the entire basin.

Similarly, the Tagus Flood Management Plan secures its scores through comprehensive legal and technical frameworks. The score of 3 for Bindingness is supported by Sections 1 and 2, which outline rigorous legal obligations, monitoring programs, and implementation mechanisms. The plan also achieves a score of 3 for Circularity; Section 3.1.3 emphasizes the improvement of infiltration and water storage conditions within urban basins, addressing flood risk and water conservation simultaneously. This integrated approach is further reinforced in Section 2.1.4.7, which promotes SuDS (Sustainable Drainage Systems) applications. By focusing on the retention, conveyance, and storage functions of urban water infrastructure to manage urban runoff, the plan treats the water cycle as a holistic system within the built environment and urban texture.

While the Tagus Basin Management Plan and the Flood Management Plan receive full marks in the Integration category by imposing direct structural constraints and zoning boundaries on the urban texture, the Drought Management Plan is assigned a score of 2. Although the latter defines spatial standards—such as xeriscaping and local storage requirements—it leaves the implementation of these standards to the discretion of local authorities and fails to mandate direct land-use obligations within sub-scale planning frameworks.

5.4 Local scale: Climate action plans, infrastructure master plans, and design guides

The confluence of dense urbanization and climate change generates complex pressures and vulnerabilities for sustainable infrastructure management and water resources planning. This is particularly pronounced in the Mediterranean climate zone, where changing precipitation patterns threaten the urban water supplies through heightened flood and drought risks. The discussion proceeds with a comparative analysis of how Istanbul and Madrid, both characterized by high urbanization rates and concentration of population and production in the Mediterranean climate zone, incorporate the rainwater cycle and SUDS into their planning processes.

Climatically, Madrid exhibits a Mediterranean continental regime, attributable to its distance from the sea and high elevation (approximately 650–700 m). The city experiences prolonged, very hot summers with low annual precipitation but is nonetheless highly exposed to flood risk from intense, sudden rainfall events. By contrast, Istanbul has a more temperate climate, moderated by marine humidity from both the Black Sea and the Sea of Marmara. The average annual precipitation in Istanbul (1950–2024) is 660.8 mm, compared with 421 mm in Madrid (1981–2010) (Appendix B, Doc 1 and 2). Approximately 90% of Madrid’s municipal water supply is drawn from dams and river basins, with the remaining 10% from groundwater wells. In Istanbul, about 99% of potable water is supplied from surface water sources, regulators and dams, while only 1% of groundwater is used in industrial or rural areas (Appendix B, Doc 3). These data indicate that both cities are strongly dependent on centralized surface water resources, with a particularly high reliance in Istanbul, underscoring their vulnerability to precipitation variability characteristic of Mediterranean climates. In this context, evaluating urban vulnerabilities requires shifting the focus from localized infrastructure toward a broader river-basin scale, which directly conditions the evolutionary hierarchy of settlements under global climate change pressures [27].

At the level of upper-scale plans, the use of Madrid’s urban rainwater infrastructure is not mandated as a direct requirement; rather, it is guided by a holistic water management framework with measurable outcome indicators. The specification of monitorable targets for water quality, flood risk, and system performance, alongside the plans’ qualitative principles, plays a key role in reinforcing this indirect binding effect. In Istanbul, by contrast, basin plans do not perform this coordinating function. As a result, rainwater infrastructure is implemented mainly through fragmented, project-based interventions tied to parcel-size standards (2021 Planned Areas Zoning Regulation Amendment) and is largely left to the discretion of local administrative authorities.

The plans and the design guide analyzed for Madrid and Istanbul have been scored as presented in Table 7, and the evaluations for each are detailed as follows:

•PIGSS is a technical plan that enables the collaborative management of urban wastewater and rainwater systems, focusing on analyzing the behavior of water during precipitation. It is a mandatory requirement for settlements with a population of 50,000 and above, in accordance with Real Decreto 665/2023 (Appendix A, Doc 1). While a final public report has not yet been prepared for Madrid, it is known that tenders for technical support and plan preparation have been opened [28]. The Plan Integral de Gestión del Sistema de Saneamiento (PIGSS) achieves a maximum score of 3 across all criteria, reflecting its role as a high-performance operational framework for local water management. Regarding bindingness, the plan’s legal force is derived directly from Real Decreto 665/2023, which transforms it from a strategic vision into a mandatory requirement for large urban settlements. Its Integration score of 3 is justified by the plan's intrinsic nature; as a technical instrument that analyzes hydraulic behavior during precipitation, it inherently provides the precise spatial standards and structural inputs necessary for the built environment. Finally, the plan secures a 3 in Circularity by enabling the collaborative management of wastewater and rainwater systems. By treating these components as an integrated cycle rather than separate disposal issues, PIGSS functions as a self-sustaining monitoring and management mechanism that ensures systemic resilience within the urban texture.

•The Madrid Climate Adaptation Action Plan (2025) functions as a strategic policy brief that identifies key urban climate risks and establishes a framework for resilience. Regarding Bindingness and Integration, the plan is evaluated with a score of 1 for both criteria; while it articulates overarching visions, it treats rainwater management as a conceptual adaptation area without defining quantitative targets or mandatory spatial standards, as these technical details and implementation mandates are primarily relegated to basin plans and other specialized instruments. However, the document achieves a score of 3 in Circularity, as it successfully integrates rainwater management within a holistic climate adaptation cycle, framing it not merely as a drainage issue but as a fundamental component of the city’s long-term systemic resilience and relational risk management (Appendix A, Doc 14).

•The Canal de Isabel II 2025-2030 Strategic Plan is a regional business plan and vision document prepared by Canal de Isabel II, the institution that oversees Madrid's water cycle, covering corporate strategy, including financing, digitalization and investments, as well as measurable targets for the urban drainage system of not only the city center but also the entire Autonomous Community of Madrid [29]. The document achieves a maximum score of 3 across all criteria due to its role as a mandatory investment roadmap that secures bindingness through allocated financing and legislative commitment. It also excels in integration and circularity by translating high-level strategy into measurable spatial targets and managing the entire water cycle as a holistic, digitalized, and integrated system.

•“Madrid’s Basic Design Guide for Sustainable Rainwater Management Systems in Green Areas and Other Open Spaces” (2018) provides comprehensive guidance for implementing SUDS for source control in Madrid. It defines numerical standards and evaluates infrastructure typologies based on topography, hydrology, rainfall and vegetation. This document establishes selection criteria to optimize sustainable drainage within the city’s specific urban context (Appendix A, Doc 15). The guide is assigned a score of 2 for both Bindingness and Integration because, while it provides essential spatial standards for urban settlements, it functions as a technical manual rather than a strictly mandatory legislative act or a direct planning instrument. However, it earns a score of 3 in Circularity for its ability to spatialize infrastructure typologies that simultaneously manage storage and conveyance, effectively addressing dual climate risks within a holistic water management framework.

Table 7. Comparative assessment of policy documents at the local scale

Istanbul has formulated a series of strategies aimed at addressing climate change and managing rainwater at the urban level. The following section will delineate these strategies in different plans.

•The Istanbul Metropolitan Municipality (IMM) Sustainable Energy and Climate Action Plan, set forth by the IMM encompasses the years 2023 to 2030. In the context of Istanbul's rainwater management, a comparative analysis was conducted of the flood vulnerabilities of the districts (based on flow retention index, flow retention amount, and flood volume) with a focus on highlighting the urban flood risk. Although SUDS and the sponge city concept against urban floods were introduced as part of adaptation actions, measurable targets were not established for this (Appendix A, Doc 16). The plan mentions the sponge city concept merely as a vision (Section 3.4.2: Adaptation actions regarding vulnerabilities), without providing a concrete implementation framework (bindingness score: 1). Although flood-related analyses are included, there are no spatial standards directly transferred to lower-scale planning (integration score: 0). Furthermore, despite referencing the sponge city approach, the plan treats rainwater as a risk and a waste product to be discharged rather than a potential resource; its primary focus remains on securing water supply through conventional dams and regulators (circularity score: 0).

•The IMM Climate Change Action Plan (2021-2030) recognizes the increasing pressure on water resources driven by urban expansion, population growth, and climate change. Although it is situated within a comprehensive adaptation agenda addressing droughts and floods, views rainwater as a potential resource, and provides guidance for lower-scale planning, the plan lacks direct enforcement mechanisms, spatial thresholds, or specific standards for these lower-tier plans. Consequently, the plan did not reach the highest performance level in the evaluation, receiving a score of 2 for each respective criterion (Appendix A, Doc 17).

•The ISKI Drinking Water and Sewage Master Plan (2023-2053) serves as the primary technical framework for Istanbul’s water infrastructure. Based on the preparatory draft report of the plan, rainwater continues to be treated primarily as a risk to be controlled rather than a strategic resource. Although sustainable urban drainage and water-sensitive city concepts are referenced, the proposed measures focus on large-scale, project-based interventions and remain weakly integrated into lower-scale spatial planning, largely overlooking urban surface runoff management at the implementation level (Appendix A, Doc 18). Consequently, the evaluation of the draft report yielded a bindingness score of 1, as it lacks a final enforcement framework; an integration score of 0, due to the disconnect with local spatial planning tools; and a circularity score of 1, reflecting a conceptual mention of resource potential that is not yet supported by systemic reuse strategies.

This comparative content analysis demonstrates that urban rainwater management is not merely a technical infrastructure issue, but a challenge of multi-scalar planning hierarchy and legal integration. Despite facing similar climatic risks, the cases of Spain and Turkey exhibit fundamental differences in how resilience is institutionalized. While Turkey stands out with a strong legal will at the national level and mandatory parcel-based applications, it is observed that this success is not effectively transferred to the local scale within the spatial planning hierarchy, as the system is fragmented by boundaries between institutional and technical jurisdictions. In contrast, the Spanish case offers an integrated "policy delivery mechanism" that translates national policy into local spatial practices through national design guides and binding basin plans.

The most striking finding of the analysis is the approach within the Turkish system that treats flood and drought as independent problems rather than a single cycle. This constitutes the primary barrier preventing the circular use of water as a "resource" and the localization of NBS. The lack of spatial indicators and national technical guides causes high-level strategic intentions to dissolve before they can be transformed into concrete urban design standards at the local level.

In conclusion, resilience in the urban rainwater cycle is possible not only by increasing parcel-based storage capacity but by establishing water management as an inseparable pillar of spatial planning. It is a critical necessity for Turkey to transition from its current "parcel-oriented technical mandate" model to a legally integrated hierarchy supported by spatial standards, extending from the basin scale to the neighborhood scale, as seen in Spain. Future planning policies should conceptualize water not as "waste" but as a strategic "spatial asset," making climate adaptation a founding principle of urban design.