Comprehensive Study Notes on Early North and West African Vernacular Architecture

Theoretical Foundations of Vernacular and Traditional Architecture

• Fundamental Definitions and Architectural Taxonomies:

  • Traditional Architecture: Architecture produced in strict accordance with customs, rituals, and beliefs passed down from generation to generation. It is intrinsically tied to material culture, localized technical skills, and ancestral knowledge to produce established building forms and typologies. It functions as the simplest form of building to address human shelter and maintains an enduring link to cultural history.
  • Vernacular Architecture: A category of architecture based on localized communal needs, indigenous construction materials, and regional traditions. Vernacular architecture accommodates the specific values, micro-economies, and daily ways of life of the culture that produces it.
  • Distinction Between Traditional and Vernacular Architecture: While both terms are frequently used interchangeably across architectural discourse, vernacular architecture tends to dynamically evolve over time, adapting to shifting environmental, technological, cultural, and historical contexts, whereas traditional architecture rigidly adheres to time-tested ancestral precedents.
  • Typology: The systematic comparative study and classification of physical, formal, spatial, and functional characteristics of the built environment into distinct categories.
  • Symbolism in Architecture: The deliberate use of physical built form, ornamentation, or spatial organization to represent an abstract philosophical, religious, or cosmological concept. It reflects the "architecture of the mind," viewing human cognition as a process through which symbols are constructed, manipulated, and projected onto physical space.
  • Indigenous Societies: Communities, human populations, or nations characterized by historical continuity and ancestral origin within a specific geographical territory, representing the original inhabitants who first settled a region.
  • Monumental Architecture: Substantial, human-made structures constructed predominantly of stone or earth that serve public, civic, or communal functions, as opposed to everyday private vernacular residences.

• Core Characteristics of Traditional Built Environments:

  • Sustains an unbroken material and spiritual link to the past.
  • Represents the most immediate, unpretentious, and direct response to essential human physiological and social needs.
  • Reflects everyday life, localized social practices, and common regional experiences.
  • Relies strictly on locally sourced, abundant materials and non-industrialized, hand-crafted artisan skills.
  • Actively modulates the macroclimate to achieve interior environmental comfort, balancing heat, light, air velocity, precipitation, humidity, and snow load.
  • Operates within a contextual architectural philosophy: "As an architect you design for the present, with an awareness of the past, for a future which is essentially unknown" (Norman Foster).

• The Eight Primary Determinants of Traditional Architectural Form:

  • Climate: Thermal swings, solar radiation, humidity, precipitation, and seasonal extremes dictate envelope mass, opening sizes, and roof profiles.
  • Technical Skills: The generational transmission of crafting methods, masonry know-how, and structural joinery determines structural potential.
  • Availability of Building Materials: Immediate access to soil, clay, stone, timber, reeds, animal hair, or snow predetermines whether structures are compressive, tensile, or trabeated.
  • Social Norms: Kinship structures, gender segregation, privacy thresholds, and clan hierarchies shape floor plans, circulation patterns, and compound layouts.
  • Economic Factors: Subsistence modes (pastoral nomadism, agriculture, trade, foraging) define storage requirements, domestic workspace, and whether a dwelling must be portable or permanent.
  • Cultural Traits: Shared belief systems, craft aesthetics, ancestral cosmologies, and domestic behavioral rituals dictate decorative motifs, spatial orientations, and compound clustering.
  • Religious Issues: Liturgical requirements, taboos against figural representation, ritual purifications, and ancestor veneration configure sacred orientations, courtyard fountains, altars, and public prayer spaces.
  • Site Qualities: Topography, natural defensive cliffs, water sources, oases, and solar exposure govern settlement placement and aggregation strategies.

Berber Traditional Architecture and Settlement Systems

• Socio-Cultural Profile and Identity:

  • Origins and Distribution: The Berbers represent the indigenous, pre-Arab population of North Africa, distributed across Morocco, Algeria, Tunisia, and Libya.
  • Self-Denomination: They refer to themselves as the Amazigh (plural: Imazighen), translating to "free people" or "noble men."
  • Language and Faith: While they preserve their ancestral mother tongue (Berber / Tamazight), historical acculturation led to widespread adoption of Arabic and French, alongside mass conversion to Islam.
  • Historical Figures: Ibn Battuta ($1304\text{--}1369$), the Moroccan Muslim Berber explorer and scholar, documented medieval societies across thousands of kilometers.
  • Settlement and Economy: Largely sedentary agrarian communities centered around oases, valleys, and mountain hillsides.
  • Antiquity: Documented Berber kingdoms date back to at least $110\,\text{BCE}$, enduring repeated military sieges, colonization, and cultural encroachments.

• Family Structure and Domestic Spatial Politics:

  • Patriarchal Kinship: Berber social structure is strictly patriarchal, designed to preserve the ownership of an undivided patrimony within the male lineage.
  • Extended Family Cohabitation: Dwellings accommodate the family patriarch, his wife, sons, daughters-in-law, unmarried or divorced daughters, the patriarch's mother, and frequently his brothers, avoiding the parceling of family land or unnecessary capital expenditure on new structures.
  • Internal Zoning: The house is organized to safeguard personal autonomy and maintain strict privacy standards for individual nuclear sub-units.

• Building Typologies:
  • Kasbah (Tighremt): A fortified castle or aristocratic redoubt characterized by thick, massive ramparts, decorated crenellations, and defensive corner towers (square or oblique in plan). The interior comprises a sequential progression of enclosures, multi-level apartments, and internal courtyards.
  • Ksar (plural: Ksour): A fortified, nucleated earthen village enclosed within continuous perimeter walls, punctuated by watchtowers, designed to protect an entire agrarian community and its collective grain reserves against regional raids.
  • Riad and Dar: The classic Berber urban or village residence organized around a private interior courtyard. Typically built across two or more vertical levels, turning blank, monolithic walls to the exterior while opening inward toward light, shade, and communal open space.
  • Troglodyte / Subterranean Courtyard Dwellings: Sub-surface excavated dwellings (found prominently in regions such as Matmata, Tunisia), where circular central courtyards are dug deep into the bedrock with residential chambers carved laterally into the perimeter earth to provide thermal inertia against scorching summer heat and cold desert winds.

• Materiality and Construction Processes:

  • Mud Brick and Pisé (Rammed Earth): Adobe and compacted earth form the load-bearing fabric. Because unfired earth is highly water-permeable, foundations and lower wall courses require systematic plastering and structural renewal after weathering events.
  • Collective Construction Labor: Erection of a dwelling is not an individualistic enterprise but a communal ritual engaging the extended family unit (men, women, and children contributing to symbolize economic solidarity) and village neighbors.
  • Two-Phase Construction Workflow:
    1. Preparation Phase: Communal site selection, extraction of earth, gathering of structural timbers, water, and straw, and logistical staging.
    2. Actual Construction Phase: Physical appropriation and structural transformation of the site, establishing foundation trenches, compressing earth, and laying adobe brick courses.
  • Ritualized Milestones: Ground layout is consecrated through ritual ceremonies, which are repeated sequentially at critical structural thresholds (e.g., setting the threshold stone, laying the lintels, finishing the roof).

• Islamic Acculturation and Architectural Synthesis:

  • Zellige Tiling: Hand-cut polychrome glazed terra-cotta tiles, precisely assembled into intricate geometric configurations, extensively finish interior walls, lower dadoes, floors, and water fountains.
  • Fountains and Ablution Infrastructure: Water, historically revered in arid Berber territory, attained heightened spiritual and functional necessity within Islam for mandatory ritual ablution (wudu) prior to daily prayer. Fountains were incorporated into public squares, mosque courtyards, and domestic patios as architectural metaphors for Paradise.
  • Mosques and Minarets: Community focal points characterized by square-plan stone or earthen minarets, stepped hypostyle prayer halls, and mihrabs oriented toward Mecca.
  • Aniconism and Decorative Arts: The Islamic prohibition against anthropomorphic and zoomorphic representation drove the mastery of geometric abstractions and intricate floral arabesques, incised and carved directly into stone, wet plaster (stucco), and cedar wood.

Bedouin Architecture: Nomadic Tensile Enclosures of Arid Deserts

• Socio-Cultural Identity and Demography:

  • Nomadic Pastoralism: The Bedouins are nomadic Arab pastoralists inhabiting the arid desert belts spanning North Africa, the Sinai Peninsula, and the Arabian Peninsula. The Arabic root of Bedouin designates them as "desert dwellers."
  • Classification of Populations:
    • The "Real" Bedouin: Full-time nomadic pastoralists who traverse open desert wilderness with herds of camels, goats, and sheep in continuous search of ephemeral pastures and deep aquifers.
    • The Fellahin: Semi-sedentary agriculturalists and traders who engage in seasonal trade during winter months and cultivate fields during the summer.
  • Territoriality: Though dismissive of modern national borders, each distinct Bedouin tribal federation claims clearly demarcated customary ancestral territories recognized by neighboring tribes.

• Tribal Structure, Ethics, and Governance:

  • Kinship Hierarchy: Social organization is constructed upon proximity of paternal male descent: the nuclear family (gio or tent unit) forms the foundational building block; several families coalesce into a clan (goum); descent groups spanning three to five generations comprise the ibn ʿamm (literally "son of an uncle"); multiple descent groups constitute the broader tribe, headed by an elder known as the Sheikh (a learned senior male).
  • Customary Law (Urf): Social behavior, livestock marks, pasture rotation, and access to wells are governed by ancient legal codes based entirely on mutual self-help and collective clan responsibility.
  • Moral Codes: High esteem is accorded to strict honor codes, generous hospitality toward travelers, and retaliatory justice (blood revenge). Earning a wage through salaried employment is culturally stigmatized as a compromise of personal independence.
  • Diet: Sustained primarily on dairy (lacteal) products (camel and goat milk), unleavened wheat flatbreads baked over hearth coals, dates, dried fruits, and occasional meat stewed with yogurt.
  • Religious Belief: Adherents of Sunni Islam, Bedouin spiritual cosmology integrates orthodox Muslim prayer with ancient folkloric beliefs in desert spirits (Jinn).

• The Black Tent (Bayt Al-Shar): Anatomy, Structural Engineering, and Furnishings:
  • Tensile Membrane: Woven by family women from hand-spun black goat hair and sheep wool. Coarse, oily goat fibers swell when wet during rains to form a watertight seal, while the loose weave permits interior smoke and desert heat to ventilate during dry weather.
  • Dimensional Hierarchy:
    • Sheikh's Tent: A monumental tensile pavilion constructed from approximately six extra-broad cloth strips, each reaching up to $75\,\text{ft}$ in length, sewn together into an expansive rectangle supported by a minimum of four central load-bearing wooden poles.
    • Modest Family Tent: A compact shelter constructed from three or four narrower cloth strips, each roughly $25\,\text{ft}$ long, erected over one or two central poles.
  • Structural Bracing and Anchoring:
    • Supported laterally by long, heavy hemp guy ropes: two secured to each structural pole, and three anchoring each outer flank.
    • On hard-packed clay soils, ropes are driven securely with wooden or metal tent pegs.
    • In soft, loose sand dunes, rope extremities are tied to massive clumps of desert brushwood and buried at least $2\,\text{ft}$ below the sand surface, acting as subterranean deadman anchors that resist heavy wind shear.
  • Internal Zoning and Gender Separation:
    • The open long side of the tent is deliberately positioned facing leeward, strictly away from prevailing desert winds.
    • Qata: Elaborately patterned, vertical hand-woven curtains suspended within the interior to divide the structure into distinct functional zones.
    • Men's Sector (Guest Chamber): In Eastern Arabia, traditionally situated on the eastern side of the tent. Open to visitors, housing the central hearth, three nested brass coffee pots, coffee roasters, cooling trays, grinders, incense burners, and the patriarch's camel saddle arranged as a guest backrest. The master's rifle is hung directly upon the central support pole.
    • Women's and Children's Sector: Shielded entirely from outside view by the qata, containing kitchen utensils, food storage, bedding, loom apparatus, and infant cradles.
  • Thermal Modulation:
    • Summer Configuration: The ruaq (perimeter cloth side curtains) are rolled upward around the tent base to promote low-level cross-ventilation while the overhead tensile roof shades the interior from direct solar heat.
    • Winter Configuration: Winter desert nights drop below $0\,^{\circ}\text{C}$. The qata and ruaq are unfurled and tightly secured around the perimeter, sealing the interior and trapping heat generated by the central wood fire.

• Mobility, Division of Labor, and Camp Assembly:
  • Nomadic Migration Logistics: Movement occurs immediately upon depletion of water wells or local foraging fields. Tents are disassembled, folded, rolled, and strapped onto the backs of male pack camels alongside baggage, water bladders, and rolled mats.
  • Gendered Division of Labor:
    • Men: Responsible for herd protection, long-distance migration planning, defense, and the physical raising of the heavy central structural timber poles.
    • Young Girls: Assigned the repetitive, precise task of driving perimeter tent pegs into the substrate.
    • Women: Responsible for the entire cycle of membrane manufacturing (shearing, carding, yarn spinning, and ground-loom weaving), general pitching, interior furnishing layout, food preparation, and fuel gathering.
  • The Assembly Drill: Executed with military-like dispatch under the direct vocal commands of the family head acting as a drillmaster:
    1. "Spread out the tent, O my people!"
    2. "Stretch out the ropes, O children!"
    3. "Spread out the carpet and the dazcashek (mattresses) and prepare the men's and women's portions of the tent!"

Dogon Architecture and Cosmology: Cliff Dwellings of Mali

• Geographic, Demographical, and Defensive Setting:
  • Territory: Located in the central plateau region of Mali, south of the Niger River bend, centered along the steep sandstone escarpment of Bandiagara.
  • Demography: An ethnic population of approximately $800{,}000$ people speaking various dialects of the Dogon language.
  • Topographical Zones: The habitat is partitioned into three sharply defined zones: the flat sandy plains, the vertical sandstone cliffs, and the elevated rocky plateau.
  • Historical Genesis: Approximately $1{,}000\,\text{years ago}$, the Dogon migrated en masse to the rugged Bandiagara cliffs, deliberately rejecting conversion to Islam. Because non-Muslims were categorized under Islamic legal frameworks as belonging to the dar al-harb (abode of war), the Dogon were routinely targeted by merchant-backed slave raids that captured women and children and killed adult men. The inaccessible walls of the escarpment provided a vertical, defensible refuge.
  • Hydrology: Settlements rely on seasonal rivulets pooling in sandstone depressions along the base of the cliffs during the brief wet season, coupled with access to the wider Niger River basin.

• Dogon Cosmology, Spiritual Hierarchy, and Religious Specialists:
  • Amma: The supreme creator deity; omniscient, benevolent, all-seeing, and the master of cosmic life and death.
  • Subordinate Deities and Totemic Cults:
    • Nommo: The ancestral offspring of Amma, revered as semi-divine water spirits and the bringers of universal order.
    • Lebe: The incarnation of the living earth, soil regeneration, and agricultural fertility.
    • Yurugu (Ogo): The mythological pale fox, representing rebellion, drought, chaos, and fallen man.
  • Core Practice: Deeply committed to ancestral veneration, balancing malevolent and benevolent bush spirits occupying wild trees and uncultivated terrain.
  • Religious Castes and Specialists:
    • Hogon: The supreme spiritual leader and village priest; an elder chosen by seniority or inheritance who lives in ritual isolation and maintains cosmic balance.
    • Kumogu: Seers and visionaries capable of foretelling communal fortunes.
    • Diviners: Specialized priests who interpret messages left by the paws of the pale fox wandering across gridded sand divination tables.
    • Dyodyonune: Herbalists and traditional medical doctors responsible for treating physical disease.
    • Dyonune: Sorcerers empowered to invoke spells and manipulate occult forces.
    • Binukedine: The Binu priest who presides over the ancestral altar of Lebe.

• Rituals, Mask Culture, and the Sigi Cycle:
  • Feast of Sowing (Bulu): Celebrated annually in April or May preceding the rains. Offerings of pearl millet from the Hogon's fields are sacrificed by the Binu priest on the Lebe altar, releasing spiritual vital force (nyama) into the seeds to ensure agricultural abundance.
  • Funerary Rites and Mortuary Beliefs:
    • Human personality consists of two spiritual components: nyama (the active life energy) and kikinu say (the soul).
    • Upon death, the soul roams erratically along the southern village periphery, the wild bush, or around its former dwelling.
    • Initial Rites: Last approximately one week immediately following physical expiration.
    • Dama Rites: The final collective ceremony terminating mourning. Involves mock battles, ancestral offerings, and the display of carved ceremonial masks by the Awa dance society. Completion of the dama releases the soul to travel to Amma's celestial paradise (Ardyenne or Amma ginu).
  • The Great Sigi (Siguí) Ceremony:
    • Occurs only once every $60\,\text{years}$, approximating the length of an adult human lifespan.
    • A seven-year roving festival passing sequentially from village to village to arrest cultural decline, heal communal animosity, and purge civic transgression.
    • A monumental Great Mask is freshly carved, consecrated, and preserved for the duration of the cycle.

• Social Structure, Castes, and Communal Ethics:
  • Patrilineal Kinship: Villages aggregate around a single patrilineage, governed by the eldest living male descendant of the founding ancestor.
  • Marriage and Divorce: Monogamy predominates, though polygyny (typically limited to a maximum of two wives) is sanctioned. Wives occupy separate individual houses within the family compound (ginna) and move into their husband's household only following the birth of their first infant. Divorce is rare after childbearing, requiring whole-village mediation; the departing woman retains custody only of her youngest nursing infant.
  • Communal Harmony Practices: Maintained through rhythmic, ritualized daily greetings where individuals inquire comprehensively about family welfare, paired with institutional reciprocal praise rituals (women praise men, men thank women, the young honor elders, and elders validate the young).
  • Endogamous Castes:
    • Blacksmiths (Ironworkers): Possess occult, ritual smelting powers; live marginalized on village edges; characteristically impoverished.
    • Leather-workers: Engage in trans-regional mercantile trade; accumulate material affluence.
    • Caste Rules: Membership is fixed by birth; practice endogamy with parallel-cousin marriage permitted; caste boys are exempted from circumcision.

• Settlement Morphologies and Anthropomorphic Symbolism:

  • The Anthropomorphic Dwelling: The layout of the individual Dogon home (ginna) physically models an anthropomorphic cosmological anatomy: configured to depict an adult male lying on his right side in the posture assumed in the mother's womb and within the ancestral marriage bed. The domestic hearth represents the head; internal storage bays correspond to the chest; lateral perimeter granaries depict the arms and legs; the central room forms the torso; and the entry vestibule signifies the phallus.
  • Cosmic Settlement Pairing: Individual Dogon villages are systematically twinned with a neighboring village, the pair conceptualized as an earthly manifestation of the duality between Heaven and Earth.
  • Cluster Density: Compounds contain upwards of $40\,\text{dwellings}$ clustered tightly together along narrow, winding paths, sharing load-bearing party walls and retaining terraces. Flat earth-and-timber roofs provide sleeping platforms during hot weather.

• Specialized Building Typologies:

  • Male Granary: Square, vertical earthen storage tower capped with a steep, conical thatched roof. Heavily fortified against moisture and rodent infiltration with raised stone floor stilts. Used exclusively to safeguard pearl millet, sorghum, and staple cereals. The sheer volume and fill-level of male granaries indicates the economic wealth and harvest security of the compound patriarch.
  • Female Granary: Outwardly similar to the male granary with a conical thatch cap, but structurally smaller, lower, and less protected from pests. A woman retains complete ownership and financial autonomy over this space; her husband is strictly forbidden entry. Contains personal trade merchandise, earnings, hand-spun cotton, ceramics, apparel, jewelry, and private emergency food reserves.
  • Tógu Nà ("House of Words"):
    • The central civic pavilion reserved exclusively for village men to escape desert heat, debate communal policies, and administer customary law.
    • Constructed with an intentionally low clearance beneath an enormous shade roof composed of eight thick layers of millet stalks supported by carved wooden posts or drystone piers.
    • The ceiling height forces occupants to remain seated or crouched; an angry participant cannot stand up rapidly, physically preventing violent outbursts when civic debates grow contentious.
  • Punulu (Menstruation Hut):
    • Located exclusively along the outer fringes of the village settlement, built by women out of lower-quality earthen construction.
    • Women are culturally designated as ritually unclean during their menstruation cycle, requiring mandatory five-day seclusion away from the domestic compound alongside their youngest children.
    • Equipped with dedicated kitchen wares that remain permanently on-site.
    • Serves an explicit reproductive signaling function: clearly visible from the surrounding agrarian fields, allowing working men to visually verify which village women are actively menstruating and thus definitively not pregnant.

Comparative Matrix: The Eight Architectural Determinants

• Cross-Societal Determinant Comparison:
  • Climate:
    • Berber: Hot, arid summers and cold, windy winters in mountainous or valley terrain. Demands high thermal mass through thick mud-brick walls and compact courtyard riads to balance wide diurnal and seasonal temperature swings.
    • Bedouin: Arid desert environment with intense daytime solar radiation and freezing winter nights. Solved via a lightweight, portable tensile membrane of black goat hair that breathes during heat and seals tightly against wind and rain.
    • Dogon: Extreme heat, intense direct insolation, and a very short rainy season. Addressed by thick stone/adobe thermal envelopes, flat living roofs used for night sleeping, and thick, insulating, eight-layered millet-stalk shade roofs over council pavilions.
  • Technical Skills:
    • Berber: Advanced load-bearing adobe masonry, rammed-earth (pisé) compaction, geometric stone carving, and intricate decorative zellige mosaic tile cutting, transmitted across generations.
    • Bedouin: Highly refined textile weaving on horizontal ground looms, cordage tensile joinery, rapid deadman anchoring into loose sand, and coordinated, ritualized drill-pitching of modular pavilions.
    • Dogon: Skilled drystone and mud-masonry construction, sophisticated figurative woodcarving (caryatid stools, door locks, structural posts), iron smelting, and complex spatial cosmology translation.
  • Availability of Building Materials:
    • Berber: Readily available local subsoils, clay, alluvial sand, straw binders, and scarce mountain cedar or palm timber.
    • Bedouin: Renewable animal byproducts: spun sheep wool, goat hair, leather hides, and hemp fibers; complete absence of timber or stone building components.
    • Dogon: Plentiful sandstone from the Bandiagara escarpment scree slopes, red clay subsoils, agricultural millet stalks, and local bush timber.
  • Social Norms:
    • Berber: Highly patriarchal domestic structure; extended multi-generational families cohabitate in centralized compounds to retain undivided family property and preserve male lineage control.
    • Bedouin: Patriarchal nomadic clans; structural gender segregation enforced inside single tents through the suspended qata cloth dividing the guest chamber from the domestic family space.
    • Dogon: Patrilineal lineage compounds headed by the oldest elder; strict isolation of endogamous occupational castes (smiths, leather-workers) and seasonal seclusion of menstruating women in peripheral punulu huts.
  • Economic Factors:
    • Berber: Sedentary oasis and terrace agriculture, requiring permanent, defensible communal grain storage fortifications (ksour) and regular, shared domestic expansion.
    • Bedouin: Mobile pastoralism (camels, goats, sheep) demanding complete structural portability where every domestic possession is packable on camelback; strong cultural prohibition against salaried work.
    • Dogon: Intensive cultivation of millet, sorghum, and onions, requiring separate elevated, rodent-proof male storage towers alongside independent storage granaries for female economic merchandise.
  • Cultural Traits:
    • Berber: Continuous preservation of ancestral Amazigh identity, defensive community solidarity, and adherence to time-tested architectural typologies worked out over generations.
    • Bedouin: Pervasive oral traditions, martial poetry, warrior honor codes, institutionalized blood revenge, and extreme sacred hospitality toward desert wayfarers.
    • Dogon: Deeply ingrained anthropomorphic architectural symbolism, strict daily communal greeting rituals, complex masquerade cycles, and the preservation of ancient traditions against historical assimilation.
  • Religious Issues:
    • Berber: Transitioned from indigenous animism to Sunni Islam; architectural integration of ablution fountains representing paradise, minarets, and aniconic geometric arabesques.
    • Bedouin: Devout Sunni Islam interwoven with indigenous supernatural beliefs regarding desert Jinn; preservation of eastward-oriented guest chambers.
    • Dogon: Resistance to Islamic conversion, preserving ancestor worship, altars to the earth deity Lebe, secret totemic shrines (Nommo), divination grids, and elaborate 60-year Sigi renewal ceremonies.
  • Site Qualities:
    • Berber: Strategically sited across diverse terrain, perched on defensive mountain ridges, rocky hillsides, or clustered around water-rich desert oases.
    • Bedouin: Constantly shifting sites located in hyper-arid plains or sand dunes, selected purely for proximity to surviving water wells and ungrazed pasture.
    • Dogon: High-altitude, vertical sandstone cliff edges and scree shelves along the Bandiagara escarpment, chosen specifically to deter slave raids and exploit seasonal cliff-base water drainage.