Indicate whether each statement below is TRUE or FALSE [] Basic assumptions of t
ID: 1714251 • Letter: I
Question
Indicate whether each statement below is TRUE or FALSE [] Basic assumptions of the unit hydrograph method are that: 1) Rainfall excess of equal durations are assumed to produce hydrographs with equivalent time base regardless of the intensity of the rain; and 2) Direct runoff ordinates for a storm of given duration are assumed directly proportional to rainfall excess volumes. Thus, twice the rainfall produces doubling of hydrographs ordinates. [] The rational method is designed to calculate runoff for very large watersheds (e.g.: Mississippi river watershed) given the runoff coefficient, rainfall intensity and watershed areas. [] In order to accurately delineate watersheds the engineer needs to take into account political boundaries and decisions. [] Low impact development strategies that are based on increased infiltration capacity are equally efficient in soils of type A and type D. [] If one of the effects of long term climate variability is an increasing trend in the mean precipitation extremes, we can expect that engineering design methods such as the Bulletin 17B will result in under-designed structures. [] While the normal distribution for flood frequency analyses is based on 3 parameters, the log-Pearson type-3 is based on 2 parameters. [] The National Capital Region is especially vulnerable to flooding due to not only the urban runoff but also storm surges and the Potomac River Flow. We have seen in class the newly implemented flood gate to protect the federal triangle for a 10,000 year flood event. [1 The D-8 algorithm is commonly used to determine flow direction and automatically delineate watersheds. Its procedure is based on the calculation of the direction of steepest descent from each neighboring cell from a DEM 1 Based on a Flow Accumulation raster cell value, we can directly determine the upstream drainage area by multiplying its value by the raster pixel area. [] Basic assumptions of the unit hydrograph method are that: 1) Rainfall excess of equal durations are assumed to produce hydrographs with equivalent time base regardless of the intensity of the rain; and 2) Direct runoff ordinates for a storm of given duration are assumed directly proportional to rainfall excess volumes. Thus, twice the rainfall produces doubling of hydrographs ordinates. [1 The Green-Ampt method is developed to calculate evapotranspiration considering the land-use cover. [] Low Impact Development (LID) strategies are designed to reduce the impact of land use change on watershed runoff and water quality. A typical example can be the National Flood Insurance Program. [] IDF curves are developed based on statistical analyses of rainfallExplanation / Answer
1. TRUE
2. FALSE
3. TRUE
4. FALSE
5. FALSE
6. FALSE
8. TRUE
9. TRUE
10. TRUE
11. TRUE