The first part of this thesis aims at defining the conditions triggering muddy floods in the Belgian loess belt. On average, each municipality is confronted with 3.6 muddy floods each year. Annual costs associated with their off-site impacts are estimated at € 16-172 millions for the entire Belgian loess belt. A topographic threshold is derived to predict the source areas of muddy floods. Furthermore, the storms required to produce a flood are, on average, smaller in May and June (25 mm) than between July and September (46 mm). This difference is explained by the variability of soil surface characteristics that determine the runoff potential of cultivated soils (soil cover by crops and residues, soil surface crusting and roughness). Steady state infiltration rates of cropland and grassed areas were characterised in the field using a 0.5 m2-portable rainfall simulator. Overall, grassed areas have a lower infiltration rate (16-23 mm h-1) than croplands (25-52 mm h-1). Muddy floods are mostly observed between May-September because of the coincidence of critical soil surface conditions for runoff generation with the most erosive storms. After an adaptation of its decision rules to the local conditions, the STREAM expert-based model provides satisfactory runoff/erosion predictions at the catchment scale. The second part of the thesis aims at evaluating the effectiveness of measures to control muddy floods. A modelling case-study showed that peak discharge was reduced by more than 40% by installing a grassed waterway and a dam at the outlet of a 300 ha-catchment. Monitoring the same catchment (2002-2007) demonstrated that the grassed waterway as well as three dams prevented any muddy flood in the downstream village despite the occurrence of several extreme storms (with a maximum return period of 150 years). Peak discharge was reduced by 69%. Specific sediment yield dropped from 3.5 t ha-1 yr-1 to a mean of 0.5 t ha-1 yr-1 after the installation of the control measures, thereby reducing drastically sediment transfer to the alluvial plain. Finally, a methodology is provided to implement grassed waterways and earthen dams in other dry valleys in the Belgian loess belt and comparable environments.

Made available in DSpace on 2014-07-29T15:01:47Z (GMT). No. of bitstreams: 1 Dissertacao parte1 Thiago Quintiliano de Castro.pdf: 5430014 bytes, checksum: f3e872648dc1cc1c6c038172a0c1138e (MD5) Previous issue date: 2011-09-22 / This study aimed to evaluate the experimental performance of three types of permeable pavements constructed in three different structural conditions in order to control runoff in urbanized areas of the city of Goiania, Goias, adapting to the legal requirements and using local manufactured materials. It was evaluated nine experimental plots of 3.2 m² as the following types: PAV - concrete block "paver", PCP - porous concrete plate and GCC - concrete block "concregrama" and the following structural conditions: I - base of sand and natural subgrade, II - base of sand and compacted subgrade and III - base of sand, gravel subbase and compacted subgrade. Using an artificial rain simulator, 18 tests were performed with two pre-defined rain, a medium intensity (69 mm / h) and a high intensity (180 mm / h). The subgrade soil and building materials were characterized, measured the surface and subsurface runoff, and moisture of the layers of the pavement. The parameters of the models of Horton and Green-Ampt were obtained by adjusting the calculated data infiltration. Combinations PCP-II, PCP-III, II-CCG, CCG-III and PAV-III showed little or no runoff. The delay and persistence in critical times of the runoff hydrograph also secured good results to the PCP, which generally showed higher soaking times (7,2 to 30,4 minutes) compared to the other types of pavement. The structure that showed the best hydrological performance was the III, whose results ranged from 0 to 0,19 for the runoff coefficient. The results showed that porous pavements evaluated in this study contribute to the reduction of runoff, because of low runoff coefficients (0 to 0,36) obtained. Constructive guidelines on the type of permeable pavement that performed better were drawn and described. / O presente trabalho teve como objetivo avaliar o desempenho experimental de três tipos de pavimentos permeáveis construídos em três condições estruturais diferentes com vistas ao controle do escoamento superficial em áreas urbanizadas do município de Goiânia, Goiás, adequando-se às exigências legais e utilizando-se de materiais provenientes de fabricantes locais. Foram avaliadas nove parcelas experimentais de 3,2 m² conforme os seguintes tipos de revestimento: PAV - Bloco de concreto maciço tipo paver , PCP Placa de concreto poroso e CCG Bloco de concreto vazado tipo concregrama , e as seguintes condições estruturais: I - base de areia e subleito natural, II - base de areia e subleito compactado e III - base de areia, sub-base de brita tipo 1 e subleito compactado. Utilizando-se de um simulador de chuva artificial, foram realizados 18 ensaios com duas chuvas pré-definidas, uma de média intensidade (69 mm/h) e outra de alta intensidade (180 mm/h). Foram caracterizados o solo do subleito e os materiais de construção, medidos os escoamentos superficial e subsuperficial, bem como a umidade das camadas dos pavimentos. Os parâmetros dos modelos de Horton e de Green-Ampt foram obtidos por meio do ajuste dos dados calculados de taxa de infiltração. Os pavimentos PCP-II, PCP-III, CCG-II, CCG-III e PAV-III apresentaram pouco ou nenhum escoamento superficial. O retardo e o prolongamento nos tempos críticos do hidrograma de escoamento superficial também garantiram bons resultados ao revestimento PCP, que no geral apresentou os maiores tempos de embebição (7,2 a 30,4 minutos) em comparação aos demais tipos de revestimento. A estrutura que apresentou o melhor desempenho hidrológico foi o Trecho III, cujos resultados variaram de 0 a 0,19 para o coeficiente de escoamento. A análise dos resultados mostrou que os pavimentos permeáveis avaliados neste trabalho contribuem à redução do escoamento superficial, em razão dos baixos coeficientes de escoamento (0 a 0,36) obtidos, assim como ao armazenamento temporário de águas de chuva e ao incremento da infiltração de água no solo urbano. As diretrizes construtivas do tipo de pavimento permeável que obteve melhor desempenho foram traçadas e descritas.