Classification of the flood severity of the Guadalquivir River in the Southwest 1of the Iberian Peninsula during the 13thto 19th centuries

1 EARLY ONLINE RELEASE The following is a manuscript that has been peer-reviewed and accepted for publication in Atmósfera. The text will be formatted and copy-edited, and the final published version may be different from this early online release. This manuscript may be downloaded, distributed and used under the provisions of the Creative Commons Attribution Non-Commercial 4.0 International license. It may be cited using the following DOI: https://doi.org/10.20937/ATM.52953 Submission date: 31 July 2020 Acceptance date: 02 June 2021 The published manuscript will replace this preliminary version at the above DOI. Atmósfera is a quarterly journal published by the Universidad Nacional Autónoma de México (UNAM) through its Centro de Ciencias de la Atmósfera in Mexico City, Mexico. ISSN 2395-8812. https://www.revistascca.unam.mx/atm 2 Classification of the flood severity of the Guadalquivir River in the Southwest 1 of the Iberian Peninsula during the 13th to 19th centuries 2 3 Leoncio GARCÍA-BARRÓN1, Mónica AGUILAR-ALBA2, Julia MORALES3, Arturo 4 SOUSA3* 5 1Department of Applied Physics II, Universidad de Sevilla, E-41012 Seville, Spain 6 2Department of Physical Geography and AGR, Universidad de Sevilla, E-41004 Seville, Spain 7 3Department of Plant Biology and Ecology, Universidad de Sevilla, E-41012 Seville, Spain 8 9 *Corresponding author: as[email protected] 10 11 12 3 Floods of the Guadalquivir River from the 13th to the 19th century 13 14 HIGHLIGHTS 15 • We study the Guadalquivir River floods in Seville from the 13th to the 19th century. 16 • For this study, the available documentary records from historical records were used. 17 • An annual severity index flood was developed based on flood impacts. 18 • Of the ten most destructive floods, five occurred between 1598 and 1701 AD. 19 • The results obtained contribute to multiple-century knowledge of historical floods. 20 21 GRAPHICAL ABSTRACT 22 23 24 25 26 27 28 29 30 31 32 33 34 35 4 Classification of the flood severity of the Guadalquivir River in the 36 Southwest of the Iberian Peninsula during the 13th to 19th centuries 37 38 Leoncio GARCÍA-BARRÓN1, Mónica AGUILAR-ALBA2, Julia MORALES3, Arturo 39 SOUSA3* 40 1Department of Applied Physics II, Universidad de Sevilla, E-41012 Seville, Spain 41 2Department of Physical Geography and AGR, Universidad de Sevilla, E-41004 Seville, Spain 42 3Department of Plant Biology and Ecology, Universidad de Sevilla, E-41012 Seville, Spain 43 *Corresponding author: [email protected] 44 ABSTRACT 45 This study estimates the flood severity between the 13th and 19th centuries on the southwestern 46 Iberian Peninsula based on the historic records of the impacts of the Guadalquivir River flooding 47 on the city of Seville (Spain). The main documentary source was “Critical history of the floods of 48 the Guadalquivir in Seville” (1878), which compiles news from different observers, who were 49 contemporaries of each flood. Regarding the methodology, it was necessary to transfer the 50 information from different documentary sources to ordinal indices, which required developing 51 allocation criteria per flood impact. From the annual severity index assigned to the different floods, 52 an interannual series was generated. Through interannual weighing of the flooding indices, it was 53 possible to deduce the durations and intensities of sequences of flood periods between 1250 and 54 1850. Of the ten floods classified as most destructive during the five centuries analysed, i.e., from 55 1280 to 1880, five occurred during little more than a century (1598-1701). The obtained results 56 contribute to knowledge on regional rainfall, as well as to historical climatology and hydrology, 57 over multiple centuries. 58 Keywords: floods, Guadalquivir River, documentary sources, historical climatology. 59 60 RESUMEN 61 Este estudio estima la severidad de las inundaciones durante los siglos XIII a XIX en el suroeste 62 de la Península Ibérica. Para ello nos basamos en las crónicas históricas de los impactos provocados 63 por las inundaciones del río Guadalquivir en la ciudad de Sevilla (España). La principal fuente 64 documental es “Historia crítica de las riadas en Sevilla” (1878) que recopila noticias de distintos 65 5 observadores contemporáneos de cada inundación. Por ello, desde el punto de vista metodológico, 66 ha sido necesario transferir la información procedente de fuentes documentales variadas a índices 67 ordinales, para hacerlas comparables. Esto implica elaborar criterios de asignación por los impactos 68 de las diferentes inundaciones. A partir del índice anual de severidad asignado a cada inundación, 69 se genera la serie interanual. Mediante la ponderación interanual de los índices de inundación se 70 deduce la duración e intensidad de las secuencias de periodos de inundación desde 1250 hasta 1850. 71 De las diez inundaciones clasificadas como más destructivas en los cinco siglos estudiados, desde 72 1280 a 1880, cinco de ellas se concentran en poco más de un siglo, entre 1598 a 1701. Los 73 resultados obtenidos contribuyen al conocimiento multisecular de la pluviometría regional y es una 74 nueva aportación a la climatología e hidrología histórica. 75 76 6 1. Introduction 77 Knowledge on the evolution of climate over past centuries, before instrumental records, is based 78 on multiple sources that provide information directly or indirectly, i.e., proxy data. Historical, 79 botanical, and geological evidence are worth sources of flood information. Wilhelm et al. (2019) 80 show the historical development of the different methodological approaches and the type of 81 information that these files provide. Fundamentally, there are two types of proxy data: natural and 82 documentary data. This study is exclusively focused on proxy data from documentary sources. One 83 of the frequently used types of documentary proxy data is ecclesial documents related to tithe and 84 rogation ceremonies. A tithe payment, i.e., an economic tax of one tenth of a harvest, shows the 85 annual agricultural production associated with meteorological factors, although it is not always 86 easy to interpret. Moreover, in the face of meteorological adversity, the Catholic Church regulated 87 liturgical celebrations of intercession: pro pluvia rogations, in the case of prolonged droughts, or 88 pro-serenitate rogations, in the case of persistent rainfall with floods (Martín-Vide and Barriendos, 89 1995; Tejedor et al., 2019). The advantage of the rogation method is that it maintained the spatial 90 and temporal uniformity of the applicable type of ceremony, which indicates the severity attributed 91 to each event (Cremades, 2017). 92 Other relevant documentary sources of historic climatology are the records and annals of 93 historians who included unique meteorological circumstances in their stories (Rodrigo et al., 2012), 94 minutes of local corporations and institutions that gathered information on exceptional situations 95 such as droughts or floods (Barriendos et al., 2019), and reports of trustees of noble houses about 96 the economic results of agriculture that they considered to be affected by meteorological conditions 97 (Fernández-Fernández et al., 2014). This information is frequently scattered and must be filtered 98 from the main focus of the set of consulted documents. In general, literary information on climatic 99 phenomena is linked to the subjectivity and inaccuracy of the chroniclers and may be influenced 100 by external factors. To develop temporal series from this information, it is necessary to establish 101 ordinal levels of intensity that allow the creation of quantifiable scales (Pfister et al., 1999). 102 Different authors with varied orientations have investigated historical floods in Europe (Brázdil 103 et al., 2006; Glaser et al., 2010; Kjeldsen et al., 2014; Benito et al., 2015; Blöschl et al., 2020), as 104 well as their frequency and intensity in the main Spanish drainage basins (Benito, et al., 2003; 105 Machado et al., 2011; Fragoso et al., 2015; Balasch et al., 2019). Regarding the floods of the 106 7 Guadalquivir River, the geomorphological studies of Uribelarrea and Benito (2008) and Baena et 107 al. (2019) are worthy to mention. Despite the large number of historical documents on the 108 Guadalquivir River floods, according to Zamora (2014) the impacts of these floods have not been 109 addressed thoroughly, unlike other European rivers, except Borja Palomo’s compilation. Among 110 the studies focusing on the historic climate of the southern Iberian Peninsula, it is worth 111 highlighting studies on South Portugal (Alcoforado et al., 2000; Do Ó and Roxo, 2008), the Doñana 112 wetlands (Sousa et al., 2010), Southern Extremadura and Andalusia (Rodrigo et al., 1999; 2012; 113 Barriendos, 2007; Rodrigo, 2007, 2017, 2018). 114 Barriendos and Rodrigo (2006) compared historic floods of the main Spanish drainage basins. 115 According to these authors, it is possible to differentiate the typology between the Atlantic and 116 Mediterranean watersheds, although the drainage basin is the adequate reference unit for the 117 analysis of the chronology of floods. Thus, the Guadalquivir basin, in the South Atlantic side of 118 the Iberian Peninsula, only experienced synchronous catastrophic floods with the Segura basin in 119 1778 A.D. and with the Douro basin in 1545 A.D (Fig. 1). García-Codrón (2004) stated that in the 120 Iberian Peninsula, the highest seasonal risk of flooding appears in spring for the central plateau 121 under Atlantic influence (Douro, Tagus and Guadiana), during autumn for the Mediterranean 122 watershed (Jucar and Segura), and in winter for the Guadalquivir basin. Therefore, this information 123 highlights the need to conduct historical climatological studies that are thoroughly focused on the 124 main basins, such as the Guadalquivir basin object of this study. 125 In southern Spain, it is possible to distinguish two causes of flooding: 126 a) Persistent rainfall due to a long and continuous period of precipitation (or melting) in Atlantic 127 basins, as the Guadalquivir basin. These are more frequent in winter. 128 b) Torrential rains caused by periods of very intense and short rains. These are frequent in 129 Mediterranean basins as a consequence of cold drops, with greater probability in the months of 130 autumn. 131 In the Guadalquivir river basin, although floods can be caused by brief torrential rainfall, they 132 are generally influenced by prolonged and persistent rains, with subsequent runoff from an upper 133 river basin. 134 The risk of flooding in the Guadalquivir basin is essentially influenced by pluviometric and 135 orographic factors. With respect to the former, it is worth highlighting an important irregularity in 136 8 precipitation at both the seasonal and interannual scales, with a high frequency of intense rainfall 137 in wide areas of the basin. The annual precipitation average for the entire watershed is of 640 mm. 138 This, however, hides very relevant variations, with over 1,000 mm/year in some areas compared 139 to other areas with only 300 mm/year (García-Barrón et al., 2011). This is mainly due to frontal 140 precipitation that responds to the entry of Atlantic storms through the Gulf of Cadiz (Vallejo, 2000). 141 Flooding in the lower Guadalquivir River basin has a high flow rate, which is surprising, given 142 the slight slope in that region and the deceleration exerted by the sinuosities of its course (García 143 Martínez, 2003). As stated by Vanney (1970), this scenario is due to the acceleration caused by the 144 local volume contributions. 145 The aim of this work is to classify the floods of the Guadalquivir River on the city of Seville 146 from the 13th to the 19th century using historical records gathered by Borja Palomo (1878). 147 2. Study area and data 148 The following sections describe the urban circumstances of the city and its relationship with the 149 river to better understand the subsequent categorisation of the impacts caused by the floods of the 150 Guadalquivir River on the city of Seville. Most of the studies that analyse the floods of the 151 Guadalquivir focus on the effects on the urban transformation of Seville and on hydraulic works 152 during the 19th and 20th centuries (Del Moral, 1991; 1992). On the other hand, studies of the floods 153 of the previous centuries are very scarce. We analyse the main source of documentary proxy data 154 used in this study (Borja Palomo, 1878) that were subsequently compared with instrumental 155 meteorological data. 156 2.1. Study area. The city of Seville and its relationship with the floods of the Guadalquivir River 157 The Guadalquivir River is the most important river on the southern part of the Iberian Peninsula 158 (657 km long). It crosses Cordoba and Seville (Fig. 1) and discharges in Sanlúcar de Barrameda, 159 next to Doñana National Park. Guadalquivir River is situated in the southwest of Spain, where there 160 is a Mediterranean climate that is influenced by the Atlantic Ocean (García-Barrón et al., 2013). 161 Figure 1 around here 162 The city of Seville (37.38°N; 5.97°W) is built on an alluvial plain. Historically, it was a walled 163 city surrounded from the northeast to the southwest by the Guadalquivir River (Fig. 2). This river 164 separates the traditional neighbourhood of Triana from the remainder of the historic urban centre 165 9 of Seville. Therefore, the extramural neighbourhood of Triana was connected to the intramural area 166 of the city of Seville by a floating bridge (or pontoon bridge) that crossed the Guadalquivir River 167 (Fig. 2). This floating bridge, originally built in 1171 A.D., consisted of a set of tall boats anchored 168 to the bottom, joined together by iron chains, with wooden columns that held the platform of the 169 bridge. By observing old lithographs, it is possible to deduce that the distance between the water 170 surface and the platform of the bridge was no more than two and a half metres. It was reported that 171 the bridge was damaged several times and even ripped and broken apart by the current in 1794 172 (Borja Palomo, 1878). 173 Figure 2 around here 174 The walls of the city of Seville have historically served two defensive purposes: military and 175 hydrological purposes. The initial construction of the wall dates from the period of Julius Caesar 176 (1st century B.C.). Since the Roman Age, it has been rebuilt and expanded. In the late Middle Ages, 177 the wall was seven kilometres long and had 166 turrets, with 19 gates and wickets. Since the 16th 178 century, its military purpose has been less important, and it was maintained to protect the city 179 against the flooding river. It is the fundamental protective element of the city. During flood events, 180 its gates were externally reinforced with caulked planks inserted in lateral guides. It is important 181 to highlight that in1868, after great political debate, the gates and walls were torn down with the 182 justification that this would favour the expansion of the city. However, this would also influence 183 the impact of floods on the city, as described in subsequent sections. 184 Similarly, the drain spindles of the city of Seville were closed during floods to prevent them 185 from working in the reverse direction (i.e., introducing water from outside of the city into the walled 186 urban centre). In the river plain of the opposite riverbank, next to the neighbourhood of Triana, 187 cloisters and monasteries were built, which appear frequently in historical records as being affected 188 by river flooding. After floods, a serious additional problem was the permanent ponding of the low 189 areas of the river plain, where poor quality water bodies formed, with pests and the risk of disease 190 transmission, as was reported for different periods by Borja Palomo (1878). 191 Two tributaries flowed through the west side of the city, which are currently channelled and 192 hidden: the Tamarguillo, currently a ring road for traffic, and the Tagarete, closer to the walls (Fig. 193 2), which crossed under the bridge that provided access to the Xerez Gate in the southwest of the 194 city. This location is a very relevant aspect since the height of the old city wall is a reference that 195 16 From the flood of 1403 to 1481 only that of 1435 was reported, which suggests that the 373 pluviometric regime for that period the Guadalquivir River Valley was characterised by scarce 374 overflow. Considering the number and effects of the floods, we can estimate that globally, over the 375 studied time period, the 15th century, except for the two last decades, was a period with the lowest 376 flood incidence. 377 16th century 378 Ten floods were recorded throughout the 16th century, although six of them took place in the last 379 decade of that century. The flood reported in 1595 was classified as a generalised catastrophe in 380 the city (Index Flood III). This suggests that the last decade of the 16th century was very rainy and 381 that the remainder of the century had very few flood events. 382 17th century 383 Although only ten floods were reported in the 17th century (in 1626, 1649 and 1683), these floods 384 can be considered among the most catastrophic floods during the analysed centuries (Index Flood 385 III). Except for 1650-1682, in which no overflow of the Guadalquivir River was recorded, the 386 remainder of the century presents a relatively uniform distribution, with a trend of approximately 387 7-10 years. Precisely, this period of 1650-1682 coincides with the first half of the Maunder 388 Minimum (1645-1715; Eddy, 1976; Usokin, 2017), which, under our criteria, supports the idea that 389 the decrease insular activity corresponded to a dry period in southern Spain, although the continuity 390 of the Maunder Minimum, from 1683 to 1715, was relatively more humid (Alcoforado et al., 2000). 391 Through the analysis of the ecclesiastical tithe between 1589 and 1708, Rodrigo (2007) 392 established that in the area of Seville, thirty years of bad harvests were recorded, of which sixteen 393 years could be attributed to excess precipitation, among other possible causes such as frost and 394 locust plagues and the Plague epidemics. In the same period, nineteen floods of different categories 395 were recorded. Over nine years, the excess rainfall coincided with floods. However, among the bad 396 harvests, such analysis did not include the serious floods of 1595 or, especially, 1626; the latter 397 was called “the year of the deluge” (“el año de diluvio” in Spanish). No floods were recorded in 398 any of the seven years classified as bad harvest years. 399 The solemn public supplications are an important means of understanding the historical 400 evolution of the climate. In the investigations based on ecclesial documents they take on a 401 remarkable weight. Although Borja Palomo (1878) collects multiple news on supplications related 402 17 to the Guadalquivir River, his analysis is even broader, since he also includes other documentary 403 sources that he directly describes the level that the water reaches in each flood and its urban and 404 social impacts. 405 18th century 406 Twelve overflows of the Guadalquivir River occurred in the 18th century, and those in1707 407 and 1758 had catastrophic effects (Index Flood III). During the second half of the 18th century, the 408 occurrence of moderate and serious events increased (Index Floods II and III). García Martínez 409 and Baena (2006) also found an increase in the frequencies of Guadalquivir River floods from 1750 410 with respect to the previous centuries. The greatest rainfall variability was detected in 1730 and 411 1780. The first years of the 1780s were very dry; during the winter and spring of 1780-1781 and 412 the spring of 1782, there were marked episodes of drought, as confirmed by the pro pluvia 413 rogations. On the other hand, strong rains prevailed from 1784 (when the floating bridge of the 414 Guadalquivir River was moved) onwards. 415 In summary, Table I shows the number of reported floods between 1280 and 1800 as a function 416 of the flood impact index assigned, the probability of occurrence per decade and the average period 417 of recurrence in years. 418 Table I around here 419 Table I shows that, on average, the city of Seville has had approximately one flood every 12 420 years, of which one every fifty-eight years had catastrophic effects. Therefore, it is possible to 421 confirm that the flood risk in the urban area of Seville was a historically usual element. Thus, 422 flooding was a consistent focus and concern for the authorities and the population. 423 4.2 Severity of the floods during the 19th century 424 Section I of Volume II (1800-1858) of Borja Palomo (1878) describes ten overflows of the 425 Guadalquivir River. The recorded documentary sources differ in the type of information they 426 provide in different years, although they are consistent in the use of platforms (“borriquetes” in 427 Spanish) raised above the floating bridge of the Guadalquivir River to connect to the 428 neighbourhood of Triana (1803, 1830 and 1841). In January 1823, the main catastrophic flood of 429 this period took place, which inundated the entire neighbourhood of Triana and reached the height 430 of the previous great flood of 1796. We can assert that in the first half of the 19th century, the 431 frequency of floods of different intensities was high. 432 18 Section II of Borja Palomo (1878) describes historical episodes of the city that were not directly 433 related to the river flooding. As a novelty, Section III provides uninterrupted data from 1858 on 434 the height (feet) reached by the river during each flooding event. Table II shows the years and 435 months of maximum overflow and the corresponding elevation over the usual level of the river. 436 Table II around here 437 Moreover, as noted in the methodology section, we used the monthly rainfall series of the San 438 Fernando Observatory (southwestern Spain) to calculate the bimonthly excess precipitation with 439 respect to the average of that in 1837-1890, coinciding with the floods. The flood of 1876-77 was 440 not used in the calculations since after the demolition of most of the gates and the walls of the city 441 in the preceding years, the river flooded the city. Therefore, without protection, there was no longer 442 a uniform criterion to compare the effects of previous floods. 443 Figure 5 shows a pair diagram between the synchronous series of bimonthly excess rainfall p 444 (l/m2) and the overflow level d (inches). Although the number of data points is small, it can be 445 observed that the dots are roughly aligned. 446 Figure 5 around here 447 The small number of events and the type of variables that led to Equation 1 do not allow 448 extrapolation to previous centuries, although the R squared explaining more than 70 % of the 449 variance (Pearson's correlation coefficient R = 0.84 p = 0.073 and the standard error of the 450 estimates is 3.78). 451 p = 9.4 d – 28.5 (1) 452 The average of the instrumental series from the 19th century shows that in the Guadalquivir 453 River Valley, the intra-annual distribution of precipitation increases in autumn until it reaches a 454 monthly maximum in November-December and decreases progressively in spring (García-Barrón 455 et al., 2013). The precipitation regime is associated with the North Atlantic Oscillation (NAO) in 456 the Iberian Peninsula (Trigo et al., 2004), which, in its negative phase, favours the entry of storms 457 in the Guadalquivir River Valley (Gallego et al., 2006; García-Barrón et al., 2018). This current 458 behaviour can be extrapolated to previous centuries (Luterbacher et al., 2002). Figure 6 shows the 459 intra-annual rainfall distribution (Fig. 6a) and the intra-annual distribution in the number of floods 460 (Fig. 6b) showing the delay in the month with the highest probability of floods (January), with 461 respect to the maximum of the intra-annual rainfall distribution (November-December).This could 462 19 be due to the fact that floods are frequently influenced by not only immediate direct rain but also 463 accumulated rain in a drainage basin. 464 Figure 6 around here 465 Between the start date of the uninterrupted instrumental series of rainfall records (1837) and 466 the year of the last reports about floods gathered by Borja Palomo (1878) it is observed the 467 following: 468 - In each of the 16 years with floods (see Appendix II), the total annual precipitation was 469 above the average precipitation of the entire period. 470 - The average annual precipitation of the years with floods was 847 mm, which is 471 significantly different from the average of 580 mm for the entire period of 1837-1878, that 472 is, 46% over the annual arithmetic mean of the same period. 473 - For this period the average rainfall in the two wettest months of the year was 125 mm in 474 November and 119 mm in December. However, in the years with floods the average of the 475 month when the flood occurred was 143 mm and the average of the previous month was 476 184 mm. Therefore, the excess of the bi-monthly accumulation corresponding to flood 477 events is 35% higher than that of the wet bimesters. 478 4.3 Interdecadal-scale estimation of the pluviometric evolution in the Guadalquivir River basin 479 based on the records of floods in Seville 480 Frequently the floods of the Guadalquivir River are due to the accumulation of intense rains for 481 several days in the context of a wide period of some weeks with rainy conditions. In general, this 482 type of temporary distribution of rainfall is usually associated with the existence of west-south- 483 west Atlantic fronts. 484 Using the results obtained in sections 4.1 and 4.2, it was possible to generate an inter-annual 485 series of the flood index from the 13th to the 19th century. From the results of the annual flood 486 indices for 1297-1796 (Fig. 4 and Appendix II), the centred moving average was calculated for 11- 487 year periods (Fig. 7). The values of the Y coordinate represent the temporal variation of the flood 488 index. This allows to establishing a comparable ordinal scale, for more than 5 centuries, which 489 estimates the historical evolution of floods in the southwestern Iberian Peninsula. 490 Figure 7 around here 491 20 Figure 7 shows a non-periodic alternation of years with flooding and non-flooding intervals. 492 During the 14th century, a moderate level of floods can be observed; however between 1580 and 493 1650 there is a long sequence of flooding. Finally, from 1680, three discontinuous pulses are shown 494 with a greater amount of flooding episodes: 1680 to 1710, 1730 to 1760 and 1770 until the end of 495 the 18th century. 496 Rodrigo et al. (1999) presented conclusions on the temporal development of precipitation in 497 southern Spain based on several types of historical reports in different localities between 1500 and 498 2000, with instrumental records for the 19th and 20th centuries. We observed a generalised 499 likelihood between their pluviometric evolution and the one obtained in the present study for the 500 same periods in both studies (1500-1800 A.D.). The authors highlighted the positive anomaly or 501 the humid period from the late 16th century to the mid-17th century. 502 Barriendos (2007), through a documentary analysis of institutional sources and ecclesiastic pro 503 pluvia rogations, used two complementary ordinal indices of precipitation and drought. This author 504 highlighted that in Seville, two periods of floods, one from 1580 to 1620 and the other from 1760 505 to 1800, occurred. He also identified two drought periods: 1560-1580 and 1660-1730. Generally, 506 his results are globally consistent with those presented in this study, with no discrepancies at the 507 multi-decadal scale. The results obtained by García Martínez and Baena (2006) from a 508 geomorphological analysis of the study of floods in the lower Guadalquivir River are also in line 509 with our results. 510 It seems probable that the effects of the Little Ice Age (LIA) on the Mediterranean latitudes 511 were markedly more humid and with greater variability with respect to those on the northern 512 latitudes of Europe (Sousa and García-Murillo, 2003). Pfister et al. (1999) stated that climate 513 change on the Iberian Peninsula could be more associated with precipitation and less associated 514 with temperature. Grove (2001) highlighted that the same climatic conditions that induced the 515 advance of glaciers during the LIA were also responsible for an increase in the frequency of floods 516 and sedimentation in Mediterranean Europe. Several studies (Barriendos and Martín-Vide, 1998; 517 Rodrigo et al., 1999, 2000) detected, with different aspects, humid periods during the LIA in 518 Andalusia (1570–1630, 1780–1800 and 1830-1870), which alternated with dry periods and with 519 great variability (Benito, 2006; Rodrigo, 2018). Similarly, different studies have detected greater 520 aridity in the climatic conditions of the Doñana Biosphere Reserve, which coincided with the end 521 21 of the last of the humid periods of the LIA on the southern Iberian Peninsula, and these conditions 522 influenced the deterioration of lagoons (Sousa et al., 2010), hygrophytic plants (Sousa et al., 2013) 523 and coastal streams (Sousa et al., 2015). 524 In comparison with other studies, based on different types of qualitative sources of information 525 and through different assignation procedures, the results of this study must be interpreted in their 526 own context. The concept of drought can result in multiple interpretations in general, which refer 527 to a deficit of precipitation. Therefore, although different authors that documented historic 528 climatology used terms that, in a simplified manner, identify with dry/rainy, these do not have an 529 unambiguous meaning, but they introduce conceptual differences depending on the applied 530 methodology and the type of precipitation variable estimated. 531 5. Conclusions 532 This study briefly presents the impact of Guadalquivir River floods on the urban area of Seville, 533 especially highlighting the city walls as a protective element against such events. These particular 534 conditions influenced the levels of impacts cited in texts. From the literary description of the 535 historical floods of the Guadalquivir River, we generated an index flood series from the late 13th 536 century to the 19th century. In addition, we created transference criteria that numerically assigned 537 three ascending levels of severity as a function of the described impacts. We developed graphs for 538 each century that show the intensity of the floods (and, complementarily, multi-annual sequences 539 with no floods). Of the ten floods classified as most destructive in the five centuries analysed (1280- 540 1880), five were concentrated during little more than a century, i.e., between 1598 and 1701. 541 We consider that a multiple-century application of floods is an adequate procedure that, in 542 addition to other proxy data, contributes to the knowledge of the historical climatic evolution on 543 the southern Iberian Peninsula. 544 Acknowledgements 545 We would like to thank the Royal Observatory of the Navy of San Fernando for providing 546 records on precipitation from its historical archive. This study was partially funded by project 547 PID2019-104343RB-I00. 548 References 549 22 Alcoforado MJ, Nunes MF, Garcia JC, Taborda JP. 2000. Temperature and precipitation 550 reconstruction in southern Portugal during the late Maunder Minimum (AD 1675–1715). The 551 Holocene 10(3): 333–340. https://doi.org/10.1191/095968300674442959 552 Baena R, Rinaldi M, García-Martínez B, Guerrero-Amador I, Nardi L. 2019. Channel adjustments 553 in the lower Guadalquivir River (southern Spain) over the last 250 years. Geomorphology 337: 554 15–30. https://doi.org/10.1016/j.geomorph.2019.03.027 555 Balasch JC, Pino D, Ruiz-Bellet JL, Tuset J, Barriendos M, Castelltort X, Peña JC. 2019. The 556 extreme floods in the Ebro River basin since 1600 CE. Science of the total environment 646: 557 645-660. https://doi.org/10.1016/j.scitotenv.2018.07.325 558 Barriendos M, Gil-Guirado S, Pino D, Tuset J, Pérez-Morales A, Alberola A, Costa J, Balasch JC, 559 Castelltort X, Mazón J, Ruiz-Bellet JL. 2019. Climatic and social factors behind the Spanish 560 Mediterranean flood event chronologies from documentary sources (14th–20th centuries). 561 Global and Planetary Change 182: 102997. https://doi.org/10.1016/j.gloplacha.2019.102997 562 Barriendos M, Martin-Vide J. 1998. Secular climatic oscillations as indicated by catastrophic 563 floods in the Spanish Mediterranean coastal area (14th-19th centuries). Climatic Change 38(4): 564 473–491. https://doi.org/10.1023/A:1005343828552 565 Barriendos M, Rodrigo FS. 2006. Study of historical flood events on Spanish rivers using 566 documentary data. Hydrological Sciences Journal 51(5): 765–783. 567 https://doi.org/10.1623/hysj.51.5.765 568 Barriendos M. 2007. Climatic Variability on Spain for past centuries. Reconstruction from 569 historical documentary sources. In: Climate Change in Andalusia: evolution and environmental 570 consequences (Sousa A, García-Barrón L, Jurado V, Eds.). Consejería de Medio Ambiente de 571 la Junta de Andalucía, Sevilla, Spain, 45–54. Available at: 572 http://www.juntadeandalucia.es/medioambiente/web/Bloques_Tematicos/Educacion_Y_Parti 573 cipacion_Ambiental/Educacion_Ambiental/el_cambio_climatico_en_andalucia/capitulo2.pdf 574 Benito G, Brázdil R, Herget J, Machado MJ. 2015. Quantitative historical hydrology in Europe. 575 Hydrology and Earth System Sciences 19(8): 3517–3539. https://doi.org/10.5194/hess-19- 576 3517-2015 577 23 Benito G, Díez-Herrero A, Fernández de Villalta M. 2003. Magnitude and frequency of flooding 578 in the Tagus basin (Central Spain) over the last millennium. Climatic Change 58(1–2): 171– 579 192. https://doi.org/10.1023/A:1023417102053 580 Benito G. 2006. Riesgos de inundaciones: tendencias históricas y perspectivas de acuerdo con el 581 cambio climático. Cuaternario y Geomorfología 20: 29–44. 582 https://core.ac.uk/download/pdf/36016472.pdf 583 Blöschl G, Kiss A, Viglione A, Barriendos M, Böhm O, Brázdil R, Coeur D, Demarée G, Llasat 584 MC, Macdonald N, Retsö D, Roald L, Schmocker-Fackel P, Amorim I, Bělínová M, Benito G, 585 Bertolin C, Camuffo D, Cornel D, Doktor R, Elleder L, Enzi S, Garcia JC, Glaser R, Hall J, 586 Haslinger K, Hofstätter M, Komma J, Limanówka D, Lun D, Panin A, Parajka J, Petrić H, Rodrigo 587 FS, Rohr C, Schönbein J, Schulte L, Silva LP, Toonen WHJ, Valent P, Waser J, Wetter O. 2020. 588 Current European flood-rich period exceptional compared with past 500 years. Nature 583: 560– 589 566. https://doi.org/10.1038/s41586-020-2478-3 590 Borja Palomo F. 1878. Historia crítica de las riadas o grandes avenidas del Guadalquivir en Sevilla 591 desde su reconquista hasta nuestros días. Excmo. Sevilla, Spain. Available at: 592 http://www.bibliotecavirtualdeandalucia.es/catalogo/es/consulta/registro.cmd?id=7818 593 Brázdil R, Kundzewicz ZW, Benito G. 2006. Historical hydrology for studying flood risk in 594 Europe. Hydrological Sciences Journal 51(5): 739–764. https://doi.org/10.1623/hysj.51.5.739 595 Cremades CV. 2017. Rogativas pro pluvia y pro serenitate en la cuenca del Segura durante la PEH: 596 la información suministrada por el Archivo Diocesano de Orihuela. In: Riesgo, desastre y 597 miedo en la península Ibérica y México durante la Edad Moderna (Alberola Romá A, Ed.). 598 Universidad de Alicante. El Colegio de Michoacán, 47-69. Available at: 599 https://rua.ua.es/dspace/bitstream/10045/71200/1/2017_Cremades-Prieto_Rogativas-pro- 600 pluvia-y-pro-serenitate.pdf 601 Del Moral L. 1991. La Obra Hidráulica en la Cuenca Baja del Guadalquivir (Siglos XVIII-XX). 602 Gestión del agua y organización del territorio. Junta de Andalucía y Universidad de Sevilla. 603 Spain. 604 Del Moral L. 1992. El Guadalquivir y la Transformación Urbana de Sevilla (Siglos XVIII-XX). 605 Sevilla. Spain. 606 24 Do Ó A, Roxo MJ. 2008. Drought events in Southern Portugal from the 12th to the 19th centuries: 607 Integrated research from descriptive sources. Natural Hazards 47(1): 55–63. 608 https://doi.org/10.1007/s11069-007-9196-0 609 Eddy JA. 1976. The Maunder Minimum. Science 192(4245): 1189-1202. 610 http://links.jstor.org/sici?sici=0036- 611 8075%2819760618%293%3A192%3A4245%3C1189%3ATMM%3E2.0.CO%3B2-V 612 Fernández-Fernández MI, Gallego MC, Domínguez-Castro F, Trigo RM, García JA, Vaquero JM, 613 González JMM, Durán JC. 2014. The climate in Zafra from 1750 to 1840: history and 614 description of weather observations. Climatic Change 126(1–2): 107–118. 615 https://doi.org/10.1007/s10584-014-1201-5 616 Fragoso M, Marques D, Santos JA, Alcoforado MJ, Amorim I, Garcia JC, Silva L, De Fátima 617 Nunes M. 2015. Climatic extremes in Portugal in the 1780s based on documentary and 618 instrumental records. Climate Research: 66(2): 141–159. https://doi.org/10.3354/cr01337 619 Gallego MC, García JA, Vaquero JM, Mateos VL. 2006. Changes in frequency and intensity of 620 daily precipitation over the Iberian Peninsula. Journal of Geophysical Research 111(D24): 621 D24105. https://doi.org/10.1029/2006JD007280 622 García Codrón J. 2004. Las ciudades españolas y el riesgo de inundación: permanencia y cambio 623 de un problema crónico. Boletín de la Asociación de Geógrafos Españoles 37: 85–99. 624 https://bage.age-geografia.es/ojs/index.php/bage/article/download/1978/1891/1959 625 García Martínez B, Baena R. 2006. El impacto de las infraestructuras de la ciudad de Sevilla sobre 626 el paisaje fluvial del río Guadalquivir. In: Ríos y ciudades europeas: espacios naturales, 627 culturales y productivos (Baena R, Guerrero I, Posada JC, López E, Eds.). I Encuentro 628 Internacional de Ciudades Fluviales Europeas. Universidad de Sevilla, Spain, 119-128. 629 https://idus.us.es/handle/11441/62088#.XxWDv3p_at0.mendeley 630 García Martínez B. 2003. Interpretación paleohidrológica (ss. XVI-XX) del tramo bajo continental 631 del río Guadalquivir a través de sus inundaciones y meandros. In: Geografía de Andalucía 632 (Asociación de Profesores de Geografía e Historia de Bachillerato de Andalucía, Eds.), Spain, 633 173–213. 634 25 García-Barrón L, Aguilar-Alba M, Morales J, Sousa A. 2018. Intra-annual rainfall variability in 635 the Spanish hydrographic basins. International Journal of Climatology 38(5): 2215–2229. 636 https://doi.org/10.1002/joc.5328 637 García-Barrón L, Aguilar-Alba M, Sousa A. 2011. Evolution of annual rainfall irregularity in the 638 southwest of the Iberian Peninsula. Theoretical and Applied Climatology 103(1): 13–26. 639 https://doi.org/10.1007/s00704-010-0280-0 640 García-Barrón L, Morales J, Sousa A. 2013. Characterization of the intra-annual rainfall and its 641 evolution (1837-2010) in the southwest of the Iberian Peninsula. Theoretical and Applied 642 Climatology 114(3–4): 445–457. https://doi.org/10.1007/s00704-013-0855-7 643 Glaser R, Riemann D, Schönbein J, Barriendos M, Brázdil R, Bertolin C, Camuffo D, Deutsch M, 644 Dobrovolný P, van Engelen A, Enzi S, Halíčková M, Koenig SJ, Kotyza O, Limanówka D, 645 Macková J, Sghedoni M, Martin B, Himmelsbach I. 2010. The variability of European floods 646 since AD 1500. Climatic Change 101(1): 235–256. https://doi.org/10.1007/s10584-010-9816- 647 7 648 Grove AT. 2001. The “Little Ice Age” and its geomorphological consequences in Mediterranean 649 Europe. Climatic Change 48(1): 121–136. https://doi.org/10.1023/A:1005610804390 650 Kjeldsen TR, Macdonald N, Lang M, Mediero L, Albuquerque T, Bogdanowicz E, Brazdil R, 651 Castellarin A, David V, Fleig A, Gül GO. 2014. Documentary evidence of past floods in Europe 652 and their utility in flood frequency estimation. Journal of Hydrology 517: 963-73. 653 https://doi.org/10.1016/j.jhydrol.2014.06.038 654 León González-Mazón P, García-Martínez B, Langa Nuño C. 2020. El estudio de las inundaciones 655 históricas en Sevilla a través de fuentes periodísticas (siglo XX). Estudios sobre el Mensaje 656 Periodístico 26(1): 177–188. https://doi.org/10.5209/esmp.67297 657 Luterbacher J, Xoplaki E, Dietrich D, Rickli R, Jacobeit J, Beck C, Gyalistras D, Schmutz C, 658 Wanner H. 2002. Reconstruction of sea level pressure fields over the Eastern North Atlantic 659 and Europe back to 1500. Climate Dynamics 18(7): 545–562. https://doi.org/10.1007/s00382- 660 001-0196-6 661 32 1608 March 1 1618 March 2 1626 January 3 1633 September 1 1642 January 1 1649 April 3 1683 January 3 1691 March 1 1697 Mai 1 18th 1707 March 3 1709 February 1 1736 April 1 1739 December 1 1740 January 0 1745 February 1 1750 October 1 1758 January 3 1777 February 2 1784 January 2 1786 March 1 1792 January 1 1796 November 2 19th 1802 December - 1804 January - 1806 April - 1821 January - 1823 January - 1830 January - 1831 January - 1838 February - 33 1839 December - 1841 January - 1843 March - 1845 January - 1846 January - 1852 December - 1855 March - 1856 January - 1858 November - 1860 December - 1862 January - 1866 March - 1867 January - 1872 January - 1876 December - 834 835 836 34 Appendix III. Other documentary sources consulted 837 Ariño F de. 1873. Sucesos de Sevilla de 1592 á 1604. Imprenta de Rafael Tarascó y Lassa. 838 Biblioteca virtual de Andalucía: Available at: 839 http://www.bibliotecavirtualdeandalucia.es/catalogo/es/consulta/registro.cmd?id=1017773 840 (accessed on September 22, 2019) 841 Barrantes Maldonado P. 1868. Corónica de rey don Enrique Tercero deste nombre en la casa de 842 Castilla y de León, que otros llaman el doliente, hijo del rey don Juan el primero. 1541. 843 Biblioteca Digital Real Academia de la Historia. Available at 844 https://bibliotecadigital.rah.es/es/consulta/registro.do?control=RAH20100000502 (accessed 845 on September 26, 2019) 846 Bernáldez A. 1870. Historia de los Reyes Católicos Don Fernando y Doña Isabel. S. XVII. 847 Biblioteca virtual de Andalucía. Available at 848 http://www.bibliotecavirtualdeandalucia.es/catalogo/es/consulta/registro.cmd?id=1000499 849 (accessed on September 6, 2019) 850 Delgado F. 1785. Leccion historico politico Médica de las Enfermedades que pueden seguirse de 851 resultas de la pasada inundacion del Guadalquivir, Memorias Académicas de la Real Sociedad 852 de Medicina y demás ciencias de Sevilla, Tomo III, pp. 58-77. 853 Nieto Piña C. 1785. Varias reflexiones sobre las inundaciones del rio en Sevilla, sus efectos y 854 causas evitables, Memorias Académicas. Tomo III. Archivo de la Regia Sociedad. Real 855 Academia de Medicina, pp. 336-360. 856 Ortiz de Zúñiga D. 1677. Anales eclesiásticos y seculares de la muy noble y muy leal ciudad de 857 Sevilla, Imprenta Real. Madrid. Biblioteca virtual Andalucía. Available at: 858 http://www.bibliotecavirtualdeandalucia.es/catalogo/es/consulta/registro.cmd?id=1013983 859 (accessed on September 11, 2019) 860 Trigueros CM. 1784. La riada. En la Ofic. de Vazquez y Comp. Available at: 861 https://archive.org/details/A253289 (accessed on September 11, 2019) 862 Vera Limon D. 1797. De los perjuicios médicos que causan las inundaciones del Guadalquivir, 863 modo de precaver y de corregirlo, Memorias Académicas de la Regia Sociedad de Medicina y 864 demás ciencias de Sevilla, leg. 1797. 865 35 Ximenez de Lorite B. 1778. Causas físicas de las inundaciones de Sevilla. Perjuicios que causan a 866 la salud pública y modo de remediarlos, Academia de Medicina de Sevilla, leg. 1778. 867 Zapata C. 1787. Si el agua de los ríos en sus inundaciones tengan algunos perjuicios para el uso 868 interno o externo de ellas, quáles sean, y modo de examinarlas, en Memorias Académicas de 869 la Regia Sociedad de Medicina y demás Ciencias de Sevilla, V, leg. 1786, pp.95-107 870 871 872 36 Tables 873 874 Table I. Distribution of floods based on the annual index flood, with probability of occurrence 875 and average recurrence period. 876 Index Flood Number Average probability of occurrence per decade Average recurrence period (years) I 23 0.44 22.6 II 12 0.23 43.3 III 9 0.17 57.8 Total 44 0.85 11.8 877 878 879 37 Table II. Month and year of the most relevant floods and the corresponding elevations of the 880 level of the river (in inches). 881 Date Nov- 1858 Dec- 1860 Jan- 1862 Jan- 1867 Jan- 1872 Dec- 1876 Elevation of the level of the river 21 12 16 28 22 37 *The impacts of this year cannot be compared with the other floods of the 19th century. 882 883 884 38 Figure captions 885 Figure 1. Location of Seville and the Guadalquivir River on the Iberian Peninsula. 886 Figure 2. View of Seville with the Guadalquivir River in the 17th century. This map shows the 887 floating bridge or bridge of boats at the lower left side and the Torre del Oro at the right end of the 888 harbour. Source: detail of the enlarged facsimile version of the Atlas Civitates Orbis Terrarum 889 (1588) by Braun and Hogenberg. It can be found online at the National Geographic Institute of 890 Spain. Available at https://www.ign.es/web/catalogo-cartoteca/resources/html/023677.html (Accessed 891 2020 April 16). 892 Figure 3. Original cover of volume I "Critical history of the floods of the Guadalquivir in Seville" 893 published in Seville in 1878. 894 Figure 4. Index flood estimated for the Guadalquivir River in Seville: a) 1290 A.D. to 15th century, 895 b) 16th century, c) 17th century and d) 18th century. 896 Figure 5. Scatter plot of the elevation of the river level, measured in inches, and bimonthly excess 897 rainfall, measured in mm, with the regression line indicated. 898 Figure 6. Intra-annual distribution: a) relative rate of monthly rainfall during the instrumental 899 period and b) intra-annual distribution in the number of floods. 900 Figure 7. Decadal-scale estimation of the flood index evolution in the Guadalquivir River basin 901 based on the flood records for Seville between 1250 and 1800 A.D. 902 903 39 Figure 1 904 905 906 907 40 Figure 2 908 909 910 911 912 41 Figure 3 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940