Flood hydrographs

The flood history in the region, including historical flood marks and information such as flood hydrographs, their dates of occurrence, and... 

The unit hydrograph should be derived from recorded flood hydrographs and their associated rainfall. 

Repeated water table measurements in a well may be presented on a hydrograph, as a function of time. In the example given in Fig. 4.7, the low water table may be interpreted as reflecting lack of recharge in the winter, and the rise may reflect snowmelt recharge followed by summer rains. Countless combinations of hydrograph shapes and modes of interpretation are possible. Knowledge of local precipitation and climate is needed for proper interpretation. Rapid response to rain or flood events may indicate... 

McCarthy, G.T. (1938). The unit hydrograph and flood routing. Conf. North Atlantic Division New London CT. US Army Corps of Engineers Vicksburg. 

Hydrographs for locations downstream of a gauging station can be constmcted by a process known as flood routing which incorporates a stream flow model and the equation of continuity to predict flow rates. The stream flow model must incorporate physical characteristics of the channel. A number of routing models are available as computer software packages. 

Storm drainage systems can also affect stream flow, as runoff is deliberately directed into nearby streams. This rapid exiting of water from the increased impervious area can quickly reduce the Is time between precipitation input and flood runoff. The resultant increase in the stream hydrograph invariably gives rise to peak discharge flows that result in local and regional flooding. 

Frequent phenomena. For frequent phenomena, flood related variables such as water level, amount of precipitation and wind speed characterize the marine, meteorological or climatological environment. The extreme values of these variables can be derived by statistical analysis of routine measurements over a network of fixed stations by international, national, local or private oceanographic, hydrographic or meteorological services. 

Flow the peak flow and the flow time history of the entire flood event (flow hydrograph). 

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