Increased urbanization causes pervious greenfields to be converted to impervious areas increasing stormwater runoff. Most of the urban floods occur because existing drainage systems are unable to handle peak flows during rainfall events. During a storm event, flood runoff will carry contaminants to receiving waters such as rivers and creeks. Engineers and scientists have combined their knowledge to introduce innovative thinking to manage the quality of urban runoff and harvest stormwater for productive purposes. The introduction of pervious pavements addresses all the principles in Water Sensitive Urban Design. A pervious pavement is a load bearing pavement structure that is permeable to water. The pervious layer sits on the top of a reservoir storage layer. Pervious pavements reduce the flood peak as well as improve the quality of stormwater at source before it is transported to receiving waters or reused productively. To be accepted as a viable solution, understanding of the influence of design parameters on the infiltration rate (both from the bedding and the sub-base) as well as strength of the pavement requires to be established. The design of a particular pavement will need to be customized for different properties of sub layer materials present in different sites. In addition, the designs will have to meet local government stormwater discharge standards. The design of drainage systems underneath pervious pavements will need to be based on the permeability of the whole pervious system. The objectives of the research project are to: • Understand the factors influencing infiltration capacities and percolation rates through the pervious surface as well as the whole pavement structure including the bedding and the sub-base using a laboratory experimental setup. • Obtain relationships between rainfall intensity, infiltration rate and runoff quantity based on the sub-grade material using a computational model to assist the design of pervious pavements. A laboratory scale pavement was constructed to develop relationships between the surface runoff and the infiltration volume from a pervious pavement with an Eco-Pavement surface. 2 to 5mm crushed gravel and 5 to 20mm open graded gravel were chosen as the bedding and sub-base material. Initial tests such as dry and wet density, crushing values, hydraulic conductivity, California Bearing Ratio tests for aggregate material were conducted before designing and constructing the pavement model. A rainfall simulator with evenly spaced 24 sprays was set up above the pervious pavement surface. The thesis presents design aspects of the laboratory scale pavement and the tests carried out in designing the pavement and the experimental procedure. The Green and Ampt model parameters to calculate infiltration were obtained from the laboratory test results from aggregate properties. Runoff results obtained from rainfall simulator tests were compared with the Green and Ampt infiltration model results to demonstrate that the Green and Ampt parameters could be successfully calculated from aggregate properties. The final infiltration rate and the cumulative infiltration volume of water were independent of the rainfall intensity once the surface is saturated. The model parameters were shown to be insensitive to the final infiltration capacity and to the total amount of infiltrated water. The Green and Ampt infiltration parameters are the most important parameters in designing pervious pavements using the PCSWMMPP model. The PCSWMMPP model is a Canadian model built specially for designing pervious pavements. This is independent of the type of sub-grade (sand or clay) determining whether the water is diverted to the urban drainage system (clay sub-grade) or deep percolation into the groundwater system (sand sub-grade). The percolation parameter in Darcy's law is important only if the infiltrated water recharges the groundwater. However, this parameter is also insensitive to the final discharge through the subgrade to the groundwater. The study concludes by presenting the design characteristics influencing runoff from a pervious pavement depending on the rainfall intensity, pavement structure and sub-grade material and a step-by step actions to follow in the design.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-11-10T13:49:36Z No. of bitstreams: 1 CÍCERO AURÉLIO GRANGEIRO LIMA - DISSERTAÇÃO PPGECA 1992..pdf: 25126677 bytes, checksum: 344ec8cc3722c36124b4e9b1b88b50b3 (MD5) / Made available in DSpace on 2018-11-10T13:49:36Z (GMT). No. of bitstreams: 1 CÍCERO AURÉLIO GRANGEIRO LIMA - DISSERTAÇÃO PPGECA 1992..pdf: 25126677 bytes, checksum: 344ec8cc3722c36124b4e9b1b88b50b3 (MD5) Previous issue date: 1992-11-12 / Testes de infiltração com infiltrômetro duplo anel de nível constante foram efetuados em 32 pontos de uma malha retangular de uma parcela agrícola da Fazenda Experimental da EMEPA - Pb. Ajustamentos as Leis de Philip e de Green e Ampt foram efetuados. Medições da granulometria, densidade aparente seca do solo e umidade volumétrica antes e depois dos testes foram também efetuadas. Utilizou-se a seguir técnicas de análises estatística clássica e geoestatística para caracterizar a variabilidade espacial dos parâmetros de infiltração obtidos pelos ajustamentos. Nenhum dos parâmetros estudados apresentou estrutura espacial definida. Correlações simples e múltiplas evidenciaram dependência da percentagem de Argila + Silte com o espaço físico, e independência entro os parâmetros de infiltração. Ilustrações sobre o efeito da variabilidade espacial sobro o ponto de vista agronômico o hidrológico são mostradas. / Infiltration tests with double-ring infiltrometers were performed in a 33 paint reiangular regular]y spaced grid of an agri cultural site. Fitting of the infiltration curve obtained by Philip and Green and Ampt laws allowed to obtain the sorptivity, the infiltration rate at steady state and the suction parameters of Green and Ampt,for each point. Measurements of pre- and post-humidi ty, granulometry and dry density were also performed. Classical statistical and geo-statistical techniques were used to characterize spatial variability. None of the parameters studied showed a defined spatial structure. Single and muitiple correlations showed a dependence between Cclay + siltD percentage with space but no correlation between parameters was obtained. I11ustrative considerations about spatial variability were ma de with agronomic and hydrologic applications.

Ce travail vise à caractériser et comparer les fonctionnements hydrodynamiques à plusieurs échelles spatiales en zones cristalline et sédimentaire de l’Ouest nigérien et par suite à proposer un modèle simple de fonctionnement hydrodynamique des bassins expérimentaux cristallins qui soit potentiellement transposable aux échelles supérieures.L’analyse qualitative du paysage montre que ces deux domaines ont des états de surface communs et spécifiques.L’étude expérimentale effectuée sur les états de surface communs (surface biologique, BIOL, d’érosion, ERO, structurale, ST-jac, et cultivée, C) montre, à l’échelle ponctuelle, que la surface ERO a la même valeur de conductivité hydraulique K dans les deux contextes. En revanche, les surfaces C et surtout ST ont des conductivités plus faibles en zone cristalline. Le suivi temporel effectué sur ces deux états de surface en zone cristalline a mis en évidence la stationnarité de la conductivité sur ST (jachère de 5 ans) durant la saison des pluies tandis qu'elle varie fortement sur la surface cultivée en fonction du calendrier cultural et du cumul de pluie. K décroit d’une valeur initiale de 170 mm/h après le sarclage à 20 mm/h (soit la conductivité mesurée sur ST) lorsque la surface sarclée reçoit un cumul de pluie de l’ordre de 70 mm. La conductivité atteint même la valeur de 10 mm/h après un cumul de pluie de 180 mm. Cette variation de la conductivité montre l’avantage à court terme du sarclage qui améliore l’infiltration mais qui à long terme tend à dégrader la surface.Les résultats obtenus à l’échelle de la surface élémentaire (10 m²) valident bien les mesures ponctuelles. La surface ERO a le même coefficient du ruissellement (Kr) en zones cristalline et sédimentaire tandis que les surfaces ST et cultivée ont un Kr plus élevé en zone cristalline. L’analyse de l’évolution temporelle du Kr de la surface cultivée du socle a montré que sur 63 événements pluvieux observés entre 2011 et 2013, 22 ont un Kr supérieur à la moyenne (qui est de 0.25) dont près de 2/3 sont observés après plus de 70 mm de pluie qui suivent le sarclage. Les résultats obtenus à ces deux échelles (ponctuelle et surface élémentaire) sont donc cohérents et montrent que la surface cultivée s’encroûte et peut ruisseler plus que la surface ST et autant que la surface ERO. A l’échelle du bassin versant (5 ha), les Kr sont plus élevés sur les bassins cristallins à cause de ces fortes valeurs de Kr des surfaces élémentaires mais aussi parce qu’ils sont composés d’autres surfaces à forte capacité ruisselante que sont la surface d’affleurement du socle altéré et la surface gravillonnaire ayant un Kr de 0.58. A ces trois échelles (ponctuelle, élémentaire, petit bassin), on note la non-dépendance du fonctionnement hydrodynamique à l'état hydrique initial.L’exploitation des résultats ponctuels obtenus sur le site cristallin (conductivité moyenne de BIOL, ERO, et ST et conductivité variable sur la surface cultivée) dans le modèle de Green et Ampt a permis de caler le potentiel de front par état de surface et décrire de manière très satisfaisante les ruissellements mesurés sur les surfaces élémentaires. Sur la base des ruissellements ainsi calculés, nous avons simulé les hydrogrammes à l’exutoire des bassins expérimentaux en assimilant le fonctionnement de ces derniers à celui des surfaces élémentaires en spatialisant leur infiltrabilité. En faisant l’hypothèse d’une ré-infiltration nulle sur les versants, nous avons appliqué une fonction de transfert simple prenant en compte la distance de chaque surface élémentaire par rapport au réseau hydrographique, une vitesse d'écoulement constante et une pluie imbibante de 3 à 4 mm devant saturer la couverture sableuse de ravine, ce qui est beaucoup moins qu'en zone sédimentaire. Finalement, les hydrogrammes simulés reproduisent assez bien les caractéristiques des hydrogrammes mesurés, ce qui offre une perspective d’application de certains principes du modèle sur de plus grands bassins. / This work aims at characterizing and comparing the hydrodynamical functioning at several spatial scales within the granitic-basement and sedimentary zones of Western Niger. Then, a simple hydrological model that could be suitable for use at larger scales is proposed and tested.Qualitatively, the two geological domains have common and specific surface features.The experimental work carried out onto common surface features (biological crust, BIOL; erosion crust, ERO; fallow structural surface, ST and cultivated, C) shows that, at the point scale, ERO has the same hydraulic conductivity K value in both contexts. On the other hand, surfaces features C and especially ST have lower K values in granitic context.Monitoring of the ST and C sites along the rainy season proved the stationarity of the ST conductivity value. On the contrary, K varies widely with the amount of rain received from an initial value of 170 mm/h after weeding down to 20 mm/h (i.e. the ST measured value) after 70 mm of rain and even 10 mm/h after 180 mm of rain. This variation shows the short-term benefit of weeding onto infiltration but a degradation of the soil surface on the long term.At the plot scale (10 m2), runoff measurements are consistent with point measurements. ERO has the same runoff coefficient (Kr) in granitic and sedimentary zones while ST and C surfaces have a higher Kr in granitic context.Runoff monitoring of the granitic site cultivated plots showed that from a total of 63 rain events between 2011 and 2013, 22 had a Kr value higher than the average value (0.25) from which 2/3 are observed after the surface had received more than 70 mm rain after weeding.Results obtained at the two scales (point and 10-m2 plot) are thus consistent and show that the cultivated surface gets crusted and may produce runoff more than fallow ST sites and as much as ERO features.At the basin scale (5 ha), Kr values are higher in the granitic site, not only because of the higher Kr value for a given surface feature but also because of the specific low-infiltrating surfaces which are granite outcrops and gravel crusts (Kr = 0.58).At the three previous scales (point, plot and small basin), runoff volume was found independent of soil initial moisture.Using the previous point-scale results in a Green-Ampt infiltration model led to calibrate the wetting front pressure head for each surface feature and to satisfactorily describe runoff volumes obtained at the plot scale.By estimating runoff with the Green-Ampt infiltration model at any given point, basin-scale hydrograms were obtained by adding the contribution of all elementary surfaces. Assuming no re-infiltration of runoff water within the basins, a simple transfer function was chosen accounting for the distance of each surface to the hydrological network, a constant water velocity of 0.05 m.s-1 and a volume of 3-4 mm of water necessary to fill the kori sand cover, which is much less than that in the sedimentary context. Finally, simulated hydrograms reproduce nicely the measured ones, which offers the perspective of applying some principles of the model to larger basins.